Optimizing Water Use Efficiency for Environmentally Sustainable Agricultural Production Systems in Semi-Arid Regions

Goals / Objectives
Obj 1: Quantify the environmental factors that affect the degree of crop drought stress. Sub-obj 1A Assess the effects of rising atmospheric CO2 concentration on crop coefficients used in deficit irrigation scheduling systems. Sub-obj 1B Relate seasonal plant stress and water use efficiency responses of crop plants to irrigation scheduling techniques using stable carbon isotope discrimination. Sub-obj 1C Identify active root areas under sub-surface irrigation to determine optimal cultivar for dryland management. Obj 2: Develop crop management strategies that enhance water use efficiency. Sub-obj 2A Quantify the effects of wind speed, tillage management, and irradiance on surface water evaporation. Sub-obj 2B Identify changes in microbial and chemical characteristics that may impact water availability and productivity in dryland production. Obj 3 Develop a framework of methods and models for quantifying and studying the risks associated with water from rainfall for dryland agriculture over the Southern High Plains and other dryland agricultural regions. Sub-obj 3A Evaluate the ability of current weather generator configurations to reproduce the distributional characteristics of Southern High Plains summer weather variability. Sub-obj 3B Run calibrated and validated cotton and sorghum crop models with both observed and stochastically generated weather inputs to generate simulated dryland yield outcomes. Sub-obj 3C Convert modeled yield outcomes generated with simulated weather data into net profit outcomes to form corresponding profit distributions for dryland cotton and sorghum production. Obj 4: Evaluate management practices that prevent soil degradation by soil erosion in semiarid cropping and rangeland systems. Sub-obj 4A Investigate soil redistribution & dust emissions from agro-ecosystems including rangelands & native plant communities under the stressors resulting from climate change. Sub-obj 4B Evaluate management systems in terms of multi-decadal erosion rates estimated from radioisotope inventories. Obj 5: Evaluate management practices to increase soil water availability and contribute to higher water and nutrient use efficiencies. Sub-obj 5A Partitioning of evapotranspiration to water evaporation from soil & crop surfaces for dryland & irrigated cropping systems across different N fertilizer management strategies. Sub-obj 5B Investigate changes in groundwater quantity & quality that may affect cropland production in semiarid & arid regions. Obj 6: Develop management practices that contribute to maintaining microbial diversity and functions needed to improve soil health, ensure ecosystem sustainability, and maintain crop productivity under a changing climate. Sub-obj 6A Compare the effects of different management practices in semiarid regions on soil health indicators including the microbial community size, diversity & functions. Sub-obj 6B Characterize the effects of climatic events on soil health & the effects of future climate change (CO2, temperature and rainfall) on agro-ecosystems by measuring root biomass, soil microbial diversity & soil organic matter pools.

Project Methods
Sustainable agriculture, with emphasis on conservation of natural resources, is a challenge in the semiarid climate of the Southern High Plains (SHP). Of concern is developing cropping systems that cope with climate change, depletion of aquifers used for irrigation, and growing seasons characterized by frequent droughts and erratic rainfall. Climate change is expected to impose general global challenges but, clearly, solutions to these problems will be site specific. Within a framework to quantify and study the risks associated with dryland agriculture, we need sustainable agricultural systems that optimize productivity, conserve water, control soil erosion and improve soil health for agricultural production in semiarid regions and in a changing climate. We will continue long-term research that identifies management practices that impact water availability in dryland farming vs. lands in the Conservation Reserve Program. Our goal is to provide agricultural producers with tools to manage limited water resources in the semi-arid environment of the SHP. New technologies for exposing crops in the field to elevated levels of atmospheric CO2 concentration will be used to monitor hourly and daily whole canopy water use efficiency by simultaneously measuring the ratio of net CO2 assimilation to evapotranspiration. Optimum irrigation scheduling techniques will be determined from stable carbon isotope discrimination while optimal cultivars for dryland agriculture will be selected by identifying and comparing active rooting areas. This multifaceted research program will provide the knowledge base for optimizing the use of scarce water resources in arid and semi-arid regions where ground water resources are being depleted.

Progress 08/09/17 to 02/14/22

Outputs
PROGRESS REPORT Objectives (from AD-416): Obj 1: Quantify the environmental factors that affect the degree of crop drought stress. Sub-obj 1A Assess the effects of rising atmospheric CO2 concentration on crop coefficients used in deficit irrigation scheduling systems. Sub-obj 1B Relate seasonal plant stress and water use efficiency responses of crop plants to irrigation scheduling techniques using stable carbon isotope discrimination. Sub-obj 1C Identify active root areas under sub-surface irrigation to determine optimal cultivar for dryland management. Obj 2: Develop crop management strategies that enhance water use efficiency. Sub-obj 2A Quantify the effects of wind speed, tillage management, and irradiance on surface water evaporation. Sub-obj 2B Identify changes in microbial and chemical characteristics that may impact water availability and productivity in dryland production. Obj 3 Develop a framework of methods and models for quantifying and studying the risks associated with water from rainfall for dryland agriculture over the Southern High Plains and other dryland agricultural regions. Sub-obj 3A Evaluate the ability of current weather generator configurations to reproduce the distributional characteristics of Southern High Plains summer weather variability. Sub-obj 3B Run calibrated and validated cotton and sorghum crop models with both observed and stochastically generated weather inputs to generate simulated dryland yield outcomes. Sub-obj 3C Convert modeled yield outcomes generated with simulated weather data into net profit outcomes to form corresponding profit distributions for dryland cotton and sorghum production. Obj 4: Evaluate management practices that prevent soil degradation by soil erosion in semiarid cropping and rangeland systems. Sub-obj 4A Investigate soil redistribution & dust emissions from agro- ecosystems including rangelands & native plant communities under the stressors resulting from climate change. Sub-obj 4B Evaluate management systems in terms of multi-decadal erosion rates estimated from radioisotope inventories. Obj 5: Evaluate management practices to increase soil water availability and contribute to higher water and nutrient use efficiencies. Sub-obj 5A Partitioning of evapotranspiration to water evaporation from soil & crop surfaces for dryland & irrigated cropping systems across different N fertilizer management strategies. Sub-obj 5B Investigate changes in groundwater quantity & quality that may affect cropland production in semiarid & arid regions. Obj 6: Develop management practices that contribute to maintaining microbial diversity and functions needed to improve soil health, ensure ecosystem sustainability, and maintain crop productivity under a changing climate. Sub-obj 6A Compare the effects of different management practices in semiarid regions on soil health indicators including the microbial community size, diversity & functions. Sub-obj 6B Characterize the effects of climatic events on soil health & the effects of future climate change (CO2, temperature and rainfall) on agro-ecosystems by measuring root biomass, soil microbial diversity & soil organic matter pools. Approach (from AD-416): Sustainable agriculture, with emphasis on conservation of natural resources, is a challenge in the semiarid climate of the Southern High Plains (SHP). Of concern is developing cropping systems that cope with climate change, depletion of aquifers used for irrigation, and growing seasons characterized by frequent droughts and erratic rainfall. Climate change is expected to impose general global challenges but, clearly, solutions to these problems will be site specific. Within a framework to quantify and study the risks associated with dryland agriculture, we need sustainable agricultural systems that optimize productivity, conserve water, control soil erosion and improve soil health for agricultural production in semiarid regions and in a changing climate. We will continue long-term research that identifies management practices that impact water availability in dryland farming vs. lands in the Conservation Reserve Program. Our goal is to provide agricultural producers with tools to manage limited water resources in the semi-arid environment of the SHP. New technologies for exposing crops in the field to elevated levels of atmospheric CO2 concentration will be used to monitor hourly and daily whole canopy water use efficiency by simultaneously measuring the ratio of net CO2 assimilation to evapotranspiration. Optimum irrigation scheduling techniques will be determined from stable carbon isotope discrimination while optimal cultivars for dryland agriculture will be selected by identifying and comparing active rooting areas. This multifaceted research program will provide the knowledge base for optimizing the use of scarce water resources in arid and semi-arid regions where ground water resources are being depleted. We made significant accomplishments from 2017 to 2022 via data compilation, model development, and establishing indexes that support management strategies for semiarid regions with limited irrigation. Within Objective 1, to quantify a major environmental factor affecting the degree of drought stress on crops, we developed a new method to expose small plants to elevated levels of atmospheric [CO2] concentration, that was adapted from previous work done with open, flow-through chambers. Using this approach, it is now possible for plant scientists to perform short-term [CO2] enrichment studies of 4 to 6 weeks or longer in duration depending on plant species. In Sub-objective 1B, we attempted to relate stable carbon isotope discrimination in extracted cotton seed oil to plant water stress. While a critical vacancy prohibited us from correlating photosynthetic leaf stable carbon isotope discrimination to that of developing fruits, we related the end-of-season stable carbon isotope signal of oil, cotton burrs, and leaves to irrigation levels. We did not mechanistically demonstrate the validity of the hypothetical underpinnings of the concept, but we empirically demonstrated the validity of the approach as a surrogate for season long water stress measurement. In Sub-objective 1C, we developed hardware to measure soil water in a 0.3-m cylinder filled with fritted clay. However, due to the critical vacancy the test to identify active roots was not pursued. Objective 2 focused on crop management strategies to enhance water use efficiency. Within Sub-objective 2A, a 15 m long wind tunnel was modified to fit 4 weighing lysimeters under high intensity lamps to study the effects of wind speed, tillage management, and irradiance on surface soil water evaporation. The lysimeters were custom built to allow a cotton module builder to press the shells into undisturbed soil. The knives on the balances were serviced and we used temperature-stable load cells to measure evaporation within 0.33 mm/day. A vented natural gas heater was used to maintain near-constant temperature and vapor pressure deficit during the winter months scheduled for evaporative testing. We are continuing this study in our next project plan. Within Sub-objective 2B, we conducted several studies that will be continued in the next project plan to establish linkages of soil biology on soil water conservation. The main accomplishment was a statistical model that compared laboratory methods to evaluate markers for bacteria vs. fungal groups, and their relationship to sites under dryland or irrigation sites within the Southern High Plains (SHP). Although the model identified irrigation- water as an important variable affecting microbes, we need more research on how these indicators are predictors of changes in soil water storage. A funded National Institute of Food and Agriculture grant, in collaboration with New Mexico State and Colorado State University will expand the geographical coverage of semiarid regions by evaluating soil health indicators in plots under cover crops and manure applications in New Mexico and Colorado. Our goal is a framework for soil health assessment in semiarid environments and to link different soil health indicators with soil functions, e.g., soil water dynamics. To meet Objective 3 goals, we used crop simulation models to estimate the risks and uncertainties of dryland production in the semiarid SHP. Sub- objective 3A tested artificial weather generators that might be used in regions where weather data to drive crop models is sparse or unavailable. However, these evaluations were time-consuming and did not produce publishable results. Instead, Sub-objective 3B model simulations were driven by the available high-quality daily weather data provided by regional Mesonet weather stations. Simulations were conducted to determine best management practices for dryland cotton and sorghum and to compare those crops profitability over a range of commodity price and production costs. These results showed sorghum to be a viable crop to cotton, or useful in cotton-sorghum crop rotations. The fiscal year (FY) 2022 Sub-objective 3C goal ⿿the completion of a SHP dryland risk analysis web application⿿ was not accomplished because the agency prohibited the operation of web servers in June 2020. Given the importance of soil water storage in semiarid agriculture, additional research was conducted in FY 2020 using crop models to evaluate the effects of increasing soil organic carbon (SOC) on soil water storage. Simulations were also conducted in FY 2021 to estimate irrigation practices that maximize the irrigated water use efficiency of SHP cotton production. Other FY 2018 research statistically evaluated field experiment data to estimate the effects of planting dates on SHP cotton yields and fiber quality. Data from a weather station at the Texas Tech University New Deal facility in FY 2020 was used to support stockyard mortality research. In FY 2019 analysis of SHP weather data was used to support a post-doctoral effort to investigate the effects of climate on soil microbial populations. In FY 2022, crop simulation studies were conducted to estimate the impacts of winter wheat cover crops on soil water content and SHP dryland cotton production. Within Objective 4 to evaluate management practices that prevent soil degradation by soil erosion, we made progress investigating soil redistribution and dust emissions from different sources including rangelands and native plant communities. We have a long-term project at the Sevilleta National Wildlife Refuge in New Mexico. Travel was granted to the site in March 2022 to reinstall the desert grassland following removal for a control burn and a collection trip is planned for the fall. Preliminary results of soil redistribution rates were published. Objective 5 deals with water quantity or quality from the Ogallala aquifer as a shared resource providing groundwater for irrigated agriculture in the SHP. We have conducted different studies for a model to explore strategies to maximize the use of water from irrigation and from rain within Sub-objective 5A and B as our efforts to reduce water withdrawn from the aquifer. We have done extensive simulation using as input data gathered from previous field experiments that measured the storage of rainfall and crop yields within major soil types in the SHP. Also, various aspects of groundwater quantity and quality were studied within Sub-objective 5C, including long-term changes of groundwater supplies, seasonal changes in water salinity, and investigation of some consequences of seasonal pumping of groundwater resources. Groundwater samples were collected from 20 wells in 5 Texas counties for a 3 to 6- year period, to investigate seasonal variations of groundwater salinity associated with active pumping during the growing season. Results showed that when wells are actively pumped, water quality can change in complex and unpredictable ways prompting further investigations of the mechanisms involved in measured seasonal water quality changes. We developed a method to compute the average deviation of the groundwater level from a nonstationary annual-average water level. Perturbation curves are observed to follow a regular pattern of declining water levels during the growing season followed by a recovery after irrigation systems are shut down. In areas with limited groundwater, farmers may temporarily shut off irrigation systems when soil water is adequate. Thus, one can often detect periods during the growing season when irrigation is paused, and the water table is allowed time to partially recover. Seasonal changes in the local volume of stored water in the Ogallala aquifer can alter the flow of natural springs along the eastern escarpment. Reductions of spring flow can reduce the supply of freshwater available for livestock production. This is important because beef is the number one agricultural product in Texas. Measurements of spring discharge over a 7-year period revealed that spring discharge follows a seasonal pattern of reduced flows during the summer and peak flows during the winter. It is likely that the combined effects of groundwater extraction for irrigation and the growth of natural vegetation contribute to the observed seasonal patterns of spring discharge. Objective 6 addressed management practices to maintain diversity to improve soil health and crop productivity under a changing climate. Results showed improved soil microbial communities depending on the cover crop that were linked to soil organic carbon (SOC) accumulation in this region. For example, SOC content was greater with oats than pea, canola, and their mixes, which was also related to higher wet aggregate stability, and higher microbial community size in oats than fallow. Soil organic matter (SOM) is central to soil health assessment due to its critical role on microbial diversity, nutrient cycling, aggregate stability, and water storage and infiltration. Our research will continue in the new project plan to address these interactions of alternative management when droughts are more frequent. Within Sub-objective 6B, we completed our simulated studies to characterize the effects of climatic events on soil health and the effects of future climate change on agroecosystems by measuring root biomass, soil microbial diversity, and SOM pools. Results indicated that an increase in CO2 could increase soil respiration and a shift in the microbial community toward higher fungi including an increase of arbuscular mycorrhizal fungi (AMF). However, other published results demonstrated decreases in AMF with droughts in 2011 and 2016 with subsequent recovery, indicating that different factors along with climate change need to be considered to determine their effects in soil biology and their impact on the overall soil health of an agroecosystem. ACCOMPLISHMENTS 01 Maximizing the irrigation productivity of the Ogallala aquifer in the U. S. Southern High Plains. The Ogallala aquifer under the Southern High Plains (SHP) is an important groundwater resource for U.S. cotton production, but because pumping rates exceed the aquifer⿿s recharge rates its water levels are steadily declining. To ensure that the aquifer⿿s remaining water is used productively, farmers need to know which irrigation practices use the aquifer⿿s water most efficiently in cotton production. To define the most efficient irrigation practices for SHP farmers, ARS scientists from Lubbock, Texas, conducted cotton crop model simulations in which the amount and timing of irrigation was independently varied during the growing season. These simulations showed that maximum irrigation water use efficiency, that is, the amount of lint yield produced per inch of applied irrigation, occurred when between 12 to 14 inches of irrigation was applied. Simulations that varied irrigation timing showed that when 12 inches was applied only during the cotton crop⿿s mid-stage reproductive and late-stage maturation periods, irrigation efficiency was increased even further. The results of this research provide important irrigation management guidelines that will allow SHP cotton producers to maximize the ⿿crop per drop⿿ of the remaining groundwater of the southern Ogallala aquifer. 02 Dryland cotton lint yield as a function of rainfall in the U.S. Southern High Plains. Agriculture in the Southern High Plains (SHP) is shifting from producing crops with a diminishing supply of irrigation- water from the Ogallala aquifer to dryland cropping systems. To establish a relation between cotton lint yield and rainfall scientists at ARS in Lubbock, Texas, used county-level values of cotton lint yield and annual rainfall from 1972 to 2018. The ratio between cotton lint yield and rainfall is called crop water productivity (CWP). In our analysis we selected 16 counties from the SHP, including Martin, Glasscock, and Midland in the south and Cochran, Lubbock,and Hockley in the north. We speculate that results from these counties are precursors of future cotton production patterns that will emerge in the SHP. Our results showed that only 2011 ⿿ a record drought with 7 inches of rain ⿿ failed to produce a dryland cotton crop. The average cotton lint yield ranged from a high of 360 lb/acre in Lubbock County to a low of 225 lb/acre in Andrews County. However, the counties with the highest CWP of 19 lb/acre per inch of rain were in Glasscock, Midland and Martin County. We conclude that management production methods used by dryland producers in these counties represent the future schemes that need to be adopted to sustain the emerging dryland cropping systems across the SHP.

Impacts
(N/A)

Publications

Li, J., Ravi, S., Wang, G., Van Pelt, R.S., Gill, T.E., Sankey, J.B. 2022. Woody plant encroachment of grassland and the reversibility of shrub dominance: Erosion, fire and feedback processes. Ecosphere. 13(3). Article e3949. http://doi.org/10.1002/ecs2.3949.
Thapa, V.R., Ghimire, R., Vanleewen, D., Acosta Martinez, V., Shukla, M. 2022. Response of soil organic matter to cover cropping in water-limited environments. Geoderma. 406. Article 115497. https://doi.org/10.1016/j. geoderma.2021.115497.
Lascano, R.J., Payton, P.R., Mahan, J.R., Goebel, T.S., Gitz, D.C. 2022. Annual rainfall and dryland cotton lint yield - Southern High Plains of Texas. Agricultural Sciences. 13:177-200. https://doi.org/10.4236/as.2022. 132014.
Bergh, E.L., Calderon, F.J., Clemensen, A.K., Durso, L.M., Eberly, J.O., Halvorson, J.J., Jin, V.L., Margenot, A.J., Stewart, C.E., Van Pelt, R.S., Liebig, M.A. 2022. Time in a bottle: Use of soil archives for understanding long-term soil change. Soil Science Society of America Journal. 86(3):520-527. https://doi.org/10.1002/saj2.20372.
Edwards, B.L., Webb, N.P., Van Zee, J.W., Courtright, E.M., Cooper, B.F., Metz, L., Herrick, J.E., Okin, G., Duniway, M.C., Tatarko, J., Tedela, N., Newingham, B.A., Pierson Jr, F.B., Toledo, D.N., Van Pelt, R.S. 2021. Parameterizing an aeolian erosion (AERO) model for rangelands. Aeolian Research. 54. Article 100769. https://doi.org/10.1016/j.aeolia.2021.100769.
Mauget, S.A., Ulloa, M., Mitchell-Mccallister, D. 2022. Simulated irrigation water productivity and related profit effects in U.S. Southern High Plains cotton production. Agricultural Water Management. 266. https:// doi.org/10.1016/j.agwat.2022.107582.
Eibedingil, I.G., Gill, T.E., Van Pelt, R.S., Tong, D.Q. 2021. Comparison of aerosol optical depth product from MODIS product collection 6.1 and AERONET in the western United States. Remote Sensing. 13(12):2316. https:// doi.org/10.3390/rs13122316.
Eibedingil, I.G., Gill, T.E., Van Pelt, R.S., Tong, D.Q. 2021. Combining optical and radar satellite imagery to investigate the surface properties and evolution of the Lordsburg Playa, New Mexico, USA. Remote Sensing. 13(17):3402. https://doi.org/10.3390/rs13173402.
Baker, J.T., Lascano, R.J., Yates, C.E., Gitz, D.C. 2022. Nighttime CO2 enrichment did not increase leaf area or shoot biomass in cotton seedlings. Agriculture and Forest Meteorology. 320. https://doi.org/10.1016/j. agrformet.2022.108931.

Progress 10/01/20 to 09/30/21

Outputs
PROGRESS REPORT Objectives (from AD-416): Obj 1: Quantify the environmental factors that affect the degree of crop drought stress. Sub-obj 1A Assess the effects of rising atmospheric CO2 concentration on crop coefficients used in deficit irrigation scheduling systems. Sub-obj 1B Relate seasonal plant stress and water use efficiency responses of crop plants to irrigation scheduling techniques using stable carbon isotope discrimination. Sub-obj 1C Identify active root areas under sub-surface irrigation to determine optimal cultivar for dryland management. Obj 2: Develop crop management strategies that enhance water use efficiency. Sub-obj 2A Quantify the effects of wind speed, tillage management, and irradiance on surface water evaporation. Sub-obj 2B Identify changes in microbial and chemical characteristics that may impact water availability and productivity in dryland production. Obj 3 Develop a framework of methods and models for quantifying and studying the risks associated with water from rainfall for dryland agriculture over the Southern High Plains and other dryland agricultural regions. Sub-obj 3A Evaluate the ability of current weather generator configurations to reproduce the distributional characteristics of Southern High Plains summer weather variability. Sub-obj 3B Run calibrated and validated cotton and sorghum crop models with both observed and stochastically generated weather inputs to generate simulated dryland yield outcomes. Sub-obj 3C Convert modeled yield outcomes generated with simulated weather data into net profit outcomes to form corresponding profit distributions for dryland cotton and sorghum production. Obj 4: Evaluate management practices that prevent soil degradation by soil erosion in semiarid cropping and rangeland systems. Sub-obj 4A Investigate soil redistribution & dust emissions from agro- ecosystems including rangelands & native plant communities under the stressors resulting from climate change. Sub-obj 4B Evaluate management systems in terms of multi-decadal erosion rates estimated from radioisotope inventories. Obj 5: Evaluate management practices to increase soil water availability and contribute to higher water and nutrient use efficiencies. Sub-obj 5A Partitioning of evapotranspiration to water evaporation from soil & crop surfaces for dryland & irrigated cropping systems across different N fertilizer management strategies. Sub-obj 5B Investigate changes in groundwater quantity & quality that may affect cropland production in semiarid & arid regions. Obj 6: Develop management practices that contribute to maintaining microbial diversity and functions needed to improve soil health, ensure ecosystem sustainability, and maintain crop productivity under a changing climate. Sub-obj 6A Compare the effects of different management practices in semiarid regions on soil health indicators including the microbial community size, diversity & functions. Sub-obj 6B Characterize the effects of climatic events on soil health & the effects of future climate change (CO2, temperature and rainfall) on agro-ecosystems by measuring root biomass, soil microbial diversity & soil organic matter pools. Approach (from AD-416): Sustainable agriculture, with emphasis on conservation of natural resources, is a challenge in the semiarid climate of the Southern High Plains (SHP). Of concern is developing cropping systems that cope with climate change, depletion of aquifers used for irrigation, and growing seasons characterized by frequent droughts and erratic rainfall. Climate change is expected to impose general global challenges but, clearly, solutions to these problems will be site specific. Within a framework to quantify and study the risks associated with dryland agriculture, we need sustainable agricultural systems that optimize productivity, conserve water, control soil erosion and improve soil health for agricultural production in semiarid regions and in a changing climate. We will continue long-term research that identifies management practices that impact water availability in dryland farming vs. lands in the Conservation Reserve Program. Our goal is to provide agricultural producers with tools to manage limited water resources in the semi-arid environment of the SHP. New technologies for exposing crops in the field to elevated levels of atmospheric CO2 concentration will be used to monitor hourly and daily whole canopy water use efficiency by simultaneously measuring the ratio of net CO2 assimilation to evapotranspiration. Optimum irrigation scheduling techniques will be determined from stable carbon isotope discrimination while optimal cultivars for dryland agriculture will be selected by identifying and comparing active rooting areas. This multifaceted research program will provide the knowledge base for optimizing the use of scarce water resources in arid and semi-arid regions where ground water resources are being depleted. We made significant progress compiling data related to management strategies for semiarid regions of lower rainfall and of diminishing irrigation-water leading to water conservation and sustaining crop yields. Within objective 1, to quantify the environmental factors that affect the degree of crop drought stress, we completed two growing seasons (field-based growth chambers) studying the effects of elevated atmospheric carbon dioxide (CO2) concentration on peanut and on cotton. This is the first available data reporting that during water-stress episodes, long-term elevated CO2 atmospheric concentrations [650 µmol CO2 m2/s] increased leaf-level light-saturated CO2 assimilation (53%), increased vegetative biomass (58%), and increased pod yield (39%) relative to ambient CO2. These results will inform how elevated CO2 atmospheric concentrations may reduce the negative impacts of repeated water stress events on rain-fed peanut in semi-arid regions at critical developmental stages. For Objective 2, related to the development of crop management strategies that enhance water use efficiency, we continued the work with the wind- tunnel and to obtain soil monoliths proposed for Sub-objective 2A. For Sub-objective 2B, data obtained from an earlier soil sampling in different fields allowed us to establish a relationship between irrigation-water and soil microbes. For example, we developed and tested a predictive model that related soil physical and chemical properties, abiotic factors, to biological responses. As an example, by comparing a DNA marker for fungi as a function of fungal fatty acid markers, the model predicted increases of 1.18, and 1.44 times per unit increase in pH and soil organic carbon (SOC), respectively, but decreases of 0.78 units relative to gravimetric water content. Although the model identified irrigation-water as an important variable affecting microbes, additional research is needed on how these indicators are predictors of changes in soil water storage. We plan to use more cost-effective ester-linked fatty acid methyl ester analyses within our indicators as both fungal and bacterial markers can be evaluated using the same soil sample. Producers can then use this information to select agronomic management options that improve the soil microbial community leading to improved soil health. Studies within Objective 3 relate to the development of a framework of methods and models for quantifying the risks associated with dryland agriculture in semi-arid regions. Our goal is to use the approach we developed to assess the economic sustainability of dryland agriculture on the Southern High Plains (SHP). In October 2021, a weather station was installed at the Texas Tech University New Deal stockyard facility to support research conducted by ARS researchers. During fiscal year 21, research was conducted using pedotransfer functions and the Decision Support System for Agrotechnology Transfer (DSSAT) crop growth (CROPGRO)- Cotton crop model to simulate the effects of increasing SOC on the water retention properties and lint yield production of two representative SHP soils. Preliminary research evaluated weather generator configurations as well as collected weather data records for future crop simulation research for stakeholders in Martin County, Texas. Within Objective 4 to evaluate management practices that prevent soil degradation by soil erosion, we continue making progress on studies to investigate soil redistribution and dust emissions from different sources including rangelands and native plant communities. Some data were received from cooperators in Arizona for microbial assessment by collaborators at George Mason University. Plans are being made to re- install equipment at one of the rangeland sites at the Sevilleta National Wildlife refuge that was removed for a controlled burn. Our research activities also included a comparison of dust data obtained with remote sensing vs ground-based network data. We made significant progress evaluating management systems in terms of multi-decadal erosion rates estimated from radioisotope inventories part of Sub-objective 4B. For example, soil cores from the Big Spring Field Station were obtained and processed for plutonium extraction. These samples, along with other core samples from locations sampled in 1947 will allow us to determine how much of the changes in soil properties may be due to soil erosion. A non- funded cooperative agreement with Northern Arizona University was extended so that we can continue to have access to their radio-laboratory. Data from all these studies will continue to improve dust source identification and implementation of management practices that reduce wind erosion. Objective 5 consists of different studies that relate to the use of a model to explore strategies to maximize the use of water from irrigation and from rain. We have done extensive simulation work using as input data gathered from previous field experiments that measured the storage of rainfall and crop yields within major soil types in the SHP. Sub- objective 5C focuses on changes in groundwater quantity and quality that may affect cropland production in semiarid and arid regions. We collected samples of water from various sources in the SHP region over the past 3 years. Results from our groundwater investigations show that most wells become more saline while wells are actively pumping. Salinity profile measurements have revealed that groundwater tends to be more saline at the bottom of a well. As a result, when a well becomes active the more saline water is mixed from below into the upper portion of the profile and the entire water column becomes more uniform and generally more saline. Measurements of the discharge from a natural spring was found to follow a seasonal pattern of diminished discharge during the summer growing season while irrigation wells are active. This result suggests that irrigation of cropland on the SHP can influence spring-fed streams in the ranchlands to the east of the SHP. With regard to our rainfall study, results suggest that there is a surprisingly weak correlation between rainfall chemistry and atmospheric conditions, such as wind speed or direction. Further analyses of rainfall samples did, however, show a significant inverse relationship between salinity and the amount of rainfall collected in the rain gauge. We made significant progress analyzing data from studies related to Objective 6 focused on the development of management practices that contribute to maintaining diversity to improve soil health, crop productivity, and ecosystem functions under a changing climate. Previous soil samplings from research plots in the SHP showed different microbial communities depending on the cover crop evaluated. These changes were also correlated to differences in the soil organic matter dynamics. For example, SOC content was 9⿿22% greater with oats than pea, canola, and their mixes, which was also related to higher wet aggregate stability (36⿿49%), and higher microbial community size (up to 41%) in oats than fallow. Our studies suggest the use of oat as a cover crop to improve soil health and resilience of cropping systems through increases in SOC accumulation in this region. Within Sub-objective 6B, we completed our simulated studies to characterize the effects of climatic events on soil health and the effects of future climate change (CO2, ambient temperature, and rainfall) on agro-ecosystems by measuring root biomass, soil microbial diversity, and soil organic matter pools. Results indicate that an increase in CO2 could cause an increase of 82% in soil respiration, and a shift in the microbial community toward higher fungi including an increase in 46% of arbuscular mycorrhizal fungi (AMF). These results may only translate to semiarid regions where soils are sandy and/or have low soil organic matter, and the overall changes in the soil microbiome, soil health, and peanut⿿s agroecosystem functioning still need to be addressed. However, we detected decreases in AMF with natural droughts in 2011 and 2016 with subsequent recovery, which shows there are different factors with climate change that need to be considered to determine their effects in soil biological health. Record of Any Impact of Maximized Teleworking Requirement: Maximized teleworking had both positive and negative impacts on our research projects. For example, travel restrictions limited our access to field sites and data collection mostly during the summer of 2020 on studies related to soil biological health, wind erosion, and water quality measurements. Restrictions to enter the laboratory limited our ability to complete certain work on new sampling systems and to perform routine maintenance on sampling systems when needed. Further, not hosting graduate students from Texas Tech University limited the labor needed for these studies. However, telework was beneficial as it allowed us to work with a flexible schedule, improving data management. For example, we had more time to work on stored data collected over years in need to be compared with other regions or datasets. Manuscript preparation has benefited from the absence of field work as has the opportunity to develop collaborative research planning and formal proposals. Two projects were funded by NASA and by NSF from proposals developed during the maximized telework. Several new proposals were also submitted within the past year including two AFRI-grants for summer internship initiatives that will help underrepresented groups including Hispanic students enrich their academic knowledge, gain valuable professional experience, and skills through hands-on learning opportunities. An additional proposal was submitted to USDA-Farm Service Agency to evaluate the Conservation Reserve Program within the next 4 years with 8 collaborators from ARS and several other universities at a national scale with total funding of 8 million dollars, and 2.5 million dollars for ARS collaborators. Overall, the levels of collaborations and research projects at national scales that these proposals will bring are exceptional. ACCOMPLISHMENTS 01 Identification of Lordsburg Playa dust source locations impairing visibility. Lordsburg Playa in southwest New Mexico is crossed by Interstate Highway 10. Since the highway was built and records kept, dozens of people have died due to crashes caused by reduced visibility from dust. The source of dust has not been identified. Therefore, a team of ARS and university scientists (University of Texas at El Paso, Hebei Normal University, and University of Tulsa) used the Portable In- situ Wind ERosion Laboratory (PI-SWERL) to test possible dust emission sources and suggest priorities for reclamation. Specific areas were found with highest dust emission potentials, which have become priority for remediation. It is expected that remediation of the sources of the fugitive dust accomplished as a result of this ARS study will save lives and improve air quality. 02 Improvement of spatially dust collection data to better detect sources of wind erosion. Dust continues to be a problem because of decreased air quality and erosion of soil from agroecosystems. Remote sensing of atmospheric dust concentrations has allowed estimates to be made between ground-based stations but uncertainties remain. An ARS scientist in Lubbock, Texas in conjunction with university scientists (George Mason University, Fairfax, Virginia; University of Texas at El Paso) compared the atmospheric dust concentrations obtained from orbiting satellites and from a ground-based dust detection network. Results indicated that satellite dust estimates are more robust at higher latitudes and that the older of the two satellite sensors is the less accurate of the two. These data may be used to adjust algorithms used to estimate dust from satellite data resulting in more accurate spatially distributed dust data with national improvements in air quality and soil health. 03 Seasonal reductions of spring discharge linked to cropland irrigation on the Southern High Plains (SHP). The Ogallala aquifer supplies groundwater for crops in the SHP and to spring-fed streams that flow through cattle ranches in the Rolling Plains to the east of the region. ARS scientists in Lubbock, Texas conducted a study to detect seasonal changes of spring discharge at the eastern edge of the SHP. Spring discharge was found to follow a seasonal pattern of declining flow during the summer growing season followed by a recovery starting in late fall and reaching maximum discharge during winter and early spring. This result suggests that irrigation of cropland in the SHP can reduce the flow of spring-fed streams in the ranchlands to the east of this region, which can reduce the amount of water available to cattle ranches located downstream of the SHP. This study will encourage more efficient use of available groundwater in this region since water is a shared resource that can influence the production of beef cattle, which is the number one agricultural product in Texas. 04 Rainfall on the Southern High Plains (SHP) varies in salt content. As the Ogallala Aquifer is gradually depleted, many farms on the SHP will be forced to shift from irrigated to rainfed (dryland) agriculture. As the region⿿s agriculture becomes increasingly dependent on rainfall, knowledge of various aspects of precipitation becomes increasingly important for agricultural producers. For example, they need to know more about the quantity of rain, the timing and distribution across rain events, and possible variations of rainfall chemistry. Therefore, an ARS scientist from Lubbock, Texas has collected rainfall samples at two locations in the SHP for the past five years. The study showed that rainfall samples exhibit a high degree of variability with respect to the concentration of dissolved salts, which can negatively affect agroecosystems. Measurements show a distinct increase in the concentration of dissolved salts with decreasing precipitation amount. A theory was derived that describes the concentration of dissolved salts in rainfall, which will help producers that are transitioning to dryland agriculture, understand natural and anthropogenic variations of rainfall chemistry that can influence crop production. 05 Linking soil microbes to water management in agroecosystems. Soil health initiatives require soil biological indicators that can be linked to essential soil functions to help producers make management decisions that will result in greater sustainability and productivity of the agroecosystem. Producers need cost effective indicators of increases in fungi relative to bacteria as this measurement can represent higher soil C sequestration, soil aggregation, and soil organic matter accumulation, which should lead to higher soil water holding capacity. Scientists from ARS in Lubbock, Texas and colleagues from Agriculture and Agri-Food Canada and the University of Florida tested a predictive model for soil physical and chemical properties, abiotic factors, and biological responses in soil samples taken from the Southern High Plains. When comparing two biological methods, the model that best predicted presence of microbial genes with DNA work as a function of microbial markers from fatty acid analyses included silt + clay, season, and irrigation as important variables affecting soil biology. More research is needed on how these indicators are predictors of soil water storage. We will now use the fatty acid analyses as it is a more cost-effective assessment compared to gene work to evaluate fungal and bacterial groups within the same soil sample. This will provide information to producers so they can select management practices linked to increases in soil water storage, using changes in a sensitive indicator, i.e., soil microbial community. 06 Increased soil organic carbon (SOC) effects on soil water retention and crop production. Increasing SOC is widely believed to increase a soil⿿s capacity to hold water, and, potentially, to increase agricultural yields in drier growing regions like the U.S. Southern High Plains (SHP) . ARS scientists from Lubbock, Texas and Texas A&M AgriLife used crop simulation models to estimate how increasing SOC impacts soil water retention and cotton lint yield production of a clay loam soil and a fine sandy loam soil. Higher SOC increased both soil⿿s ability to hold water, but those effect⿿s magnitudes were considerably less than previously expected. As surface SOC levels in both soils increased, the sandier soil⿿s average simulated cotton lint yields were basically unchanged, while yields simulated with the clay loam actually decreased. This work showed that increased SOC had a minor effect of soil water retention in the two soils, and a neutral or negative effect on cotton lint yield. As a result, soil conservation management practices intended to increase SOC may not have the desired effect of increasing cotton lint yields and profits. 07 Modeling demonstrated how soil conservation practices can enhance soil water content for two predominant soil series in the Texas High Plains (THP). Due to a decline of irrigation-water from the Ogallala aquifer, producers in this region are transitioning from deficit-irrigation to dryland production and need management practices to store water in the soil from precipitation. Scientists from ARS in Lubbock, Texas evaluated the daily and annual water balance for three scenarios of rain (dry, average, and wet) and two major soil series (Pullman and Amarillo) in the THP. The evaluation was done with the mechanistic simulation model Energy and Water Balance (ENWATBAL). Results showed that in years with average and high precipitation, storage of rainfall in the profile occurred in the Pullman but not in the Amarillo series. The next step is to use the ENWATBAL model to quantify the effect of furrow dikes on soil water storage as a function of rainfall frequency and amount. However, producers will benefit from results that the use of furrow dikes, minimum tillage, and crop covers enhances the storage of rainfall in the soil for subsequent use by the crop for both major soil series of the THP.

Impacts
(N/A)

Publications

Burke, J., Lewis, K., Ritchie, G.L., DeLaune, P.B., Keeling, W.J., Acosta- Martinez, V., Moore, J., McLendon, T. 2021. Net positive soil water content following cover crops with no tillage in irrigated semi-arid cotton production. Soil and Tillage Research. 208. https://doi.org/10.1016/ j.still.2020.104869.
Ale, S., Himanshu, S., Mauget, S.A., Hudson, D., Goebel, T.S., Liu, B., Baumhardt, R.L., Bordovsky, J., Brauer, D.K., Lascano, R.J., Gitz, D.C. 2021. Simulated dryland cotton yield response to selected scenario factors associated with soil health. Frontiers in Sustainable Food Systems. https:/ /doi.org/10.3389/fsufs.2020.617509.
Stout, J.E. 2020. Seasonal patterns of spring discharge at silver falls, crosby county, texas. Texas Journal of Science. 72(1). Article 6. https:// doi.org/10.32011/txjsci_72_1_Article6.
Perez-Guzman, L., Phillips, L.A., Acevedo, M.A., Acosta Martinez, V. 2020. Comparing biological methods for soil health assessments: EL-FAME, enzyme activities, and qPCR. Soil Science Society of America Journal. 85(3):636- 653. https://doi.org/10.1002/saj2.20211.
Thapa, V.R., Ghimire, R., Acosta Martinez, V., Marslis, M.A., Schipanski, M. 2020. Cover crop biomass and species affect soil microbial community structure and enzymatic activities in semiarid cropping systems. Applied Soil Ecology. 157:103735. https://doi.org/10.1016/j.apsoil.2020.103735.
Li, C., Veum, K.S., Goyne, K., Nunes, M.R., Acosta Martinez, V. 2021. A chronosequence of soil health under tallgrass prairie reconstruction. Applied Soil Ecology. 164. Article 103939. https://doi.org/10.1016/j. apsoil.2021.103939.
Otuya, R., Slaughter, L., West, C., Deb, S., Acosta Martinez, V. 2020. Compost and legume management differently alter soil microbial abundance and soil carbon in semi-arid pastures. Soil Science Society of America Journal. 85(3):654-664. https://doi.org/10.1002/saj2.20215.
Perez-Guzman, L., Phillips, L.A., Seuradge, B.J., Agomoh, I., Drury, C.F., Acosta Martinez, V. 2021. An evaluation of biological soil health indicators in four long-term continuous agroecosystems in Canada. Agrosystems, Geosciences & Environment. 4(2):1-13. https://doi.org/10.1002/ agg2.20164.
Mauget, S.A., Himanshu, S., Goebel, T.S., Ale, S., Lascano, R.J., Gitz, D. C. 2021. Soil and soil organic carbon effects on simulated Southern High Plains dryland cotton production. Soil and Tillage Research. 212. https:// doi.org/10.1016/j.still.2021.105040.
Broughton, K., Payton, P.R., Baker, J.T., Yates, C.E., Tan, D., Tissue, D., Bange, M. 2020. Effects of elevated CO2 and warmer temperature on early- season field-grown cotton in high-input systems. Crop Science. https://doi. org/10.1002/csc2.20313.
Allen, L.H., Boote, K.J., Jones, J.W., Jones, P.H., Pickering, N.B., Baker, J.T., Vu, J.C., Gesch, R.W., Thomas, J.M.G., Prasad, V.P. 2020. Sunlit, controlled-environment chambers are essential for comparing plant responses to various climates. Agronomy Journal. 112(6):4531-4549. https:// doi.org/10.1002/agj2.20428.
Sapkota, M., Young, J., Slaughter, L., Acosta Martinez, V., Coldren, C. 2021. Soil microbial biomass and composition from urban landscapes in a semiarid climate. Applied Soil Ecology. 158. https://doi.org/10.1016/j. apsoil.2020.103810.

Progress 10/01/19 to 09/30/20

Outputs
Progress Report Objectives (from AD-416): Obj 1: Quantify the environmental factors that affect the degree of crop drought stress. Sub-obj 1A Assess the effects of rising atmospheric CO2 concentration on crop coefficients used in deficit irrigation scheduling systems. Sub-obj 1B Relate seasonal plant stress and water use efficiency responses of crop plants to irrigation scheduling techniques using stable carbon isotope discrimination. Sub-obj 1C Identify active root areas under sub-surface irrigation to determine optimal cultivar for dryland management. Obj 2: Develop crop management strategies that enhance water use efficiency. Sub-obj 2A Quantify the effects of wind speed, tillage management, and irradiance on surface water evaporation. Sub-obj 2B Identify changes in microbial and chemical characteristics that may impact water availability and productivity in dryland production. Obj 3 Develop a framework of methods and models for quantifying and studying the risks associated with water from rainfall for dryland agriculture over the Southern High Plains and other dryland agricultural regions. Sub-obj 3A Evaluate the ability of current weather generator configurations to reproduce the distributional characteristics of Southern High Plains summer weather variability. Sub-obj 3B Run calibrated and validated cotton and sorghum crop models with both observed and stochastically generated weather inputs to generate simulated dryland yield outcomes. Sub-obj 3C Convert modeled yield outcomes generated with simulated weather data into net profit outcomes to form corresponding profit distributions for dryland cotton and sorghum production. Obj 4: Evaluate management practices that prevent soil degradation by soil erosion in semiarid cropping and rangeland systems. Sub-obj 4A Investigate soil redistribution & dust emissions from agro- ecosystems including rangelands & native plant communities under the stressors resulting from climate change. Sub-obj 4B Evaluate management systems in terms of multi-decadal erosion rates estimated from radioisotope inventories. Obj 5: Evaluate management practices to increase soil water availability and contribute to higher water and nutrient use efficiencies. Sub-obj 5A Partitioning of evapotranspiration to water evaporation from soil & crop surfaces for dryland & irrigated cropping systems across different N fertilizer management strategies. Sub-obj 5B Investigate changes in groundwater quantity & quality that may affect cropland production in semiarid & arid regions. Obj 6: Develop management practices that contribute to maintaining microbial diversity and functions needed to improve soil health, ensure ecosystem sustainability, and maintain crop productivity under a changing climate. Sub-obj 6A Compare the effects of different management practices in semiarid regions on soil health indicators including the microbial community size, diversity & functions. Sub-obj 6B Characterize the effects of climatic events on soil health & the effects of future climate change (CO2, temperature and rainfall) on agro-ecosystems by measuring root biomass, soil microbial diversity & soil organic matter pools. Approach (from AD-416): Sustainable agriculture, with emphasis on conservation of natural resources, is a challenge in the semiarid climate of the Southern High Plains (SHP). Of concern is developing cropping systems that cope with climate change, depletion of aquifers used for irrigation, and growing seasons characterized by frequent droughts and erratic rainfall. Climate change is expected to impose general global challenges but, clearly, solutions to these problems will be site specific. Within a framework to quantify and study the risks associated with dryland agriculture, we need sustainable agricultural systems that optimize productivity, conserve water, control soil erosion and improve soil health for agricultural production in semiarid regions and in a changing climate. We will continue long-term research that identifies management practices that impact water availability in dryland farming vs. lands in the Conservation Reserve Program. Our goal is to provide agricultural producers with tools to manage limited water resources in the semi-arid environment of the SHP. New technologies for exposing crops in the field to elevated levels of atmospheric CO2 concentration will be used to monitor hourly and daily whole canopy water use efficiency by simultaneously measuring the ratio of net CO2 assimilation to evapotranspiration. Optimum irrigation scheduling techniques will be determined from stable carbon isotope discrimination while optimal cultivars for dryland agriculture will be selected by identifying and comparing active rooting areas. This multifaceted research program will provide the knowledge base for optimizing the use of scarce water resources in arid and semi-arid regions where ground water resources are being depleted. Our team made considerable progress in studies related to: data management and modeling; soil and dust samplings; and in greenhouse experiments. For example, within Objective 1, two complete growing seasons studying the effects of elevated atmospheric carbon dioxide (CO2) concentration on peanut and cotton were completed. Results from these experiments will provide information on the effects of rising CO2 concentration on crop coefficients used in deficit-irrigation scheduling systems. Twenty-five diverse cotton isolines with dates of introduction spanning a century were grown in the field under controlled deficit irrigation. In addition, genetically modified cotton with selected traits thought to affect water use efficiency were grown. Leaves were processed for stable carbon isotope analysis. We will continue with the extraction of cotton seed oil and the processing of cotton leaves and seeds from a single cultivar grown under several irrigation regimes when we return to work. Additionally, we built a prototype instrument to measure soil water content with a circular array of sensors. This is part of studies to identify active root areas under sub-surface drip irrigation to determine an optimal cultivar for dryland management. We modified polyvinyl chloride pots with 3-D printed ports that can be inserted into the pot at varying heights. Various 3-D printed ports were designed and tested to allow free water flow through the end of the port without allowing the sand and fritted clay to enter and clog the port. A 2 x 5 cm filter paper was found to be the smallest size that would absorb enough water for the isotopic extraction and analysis. We were able to determine that the minimum time to achieve full extraction of the water collected was 30 minutes. This is an important finding as the fast extraction time will facilitate processing the large number of samples that will result from these experiments. Accordingly, as we return to work we will resume the greenhouse and laboratory experiments from this objective. Within Objective 2, studies to identify changes in soil microbial and chemical characteristics that impact water availability in dryland production could not proceed as originally planned and were modified. For example, weekly measurements of soil water content measured with neutron probes that were going to be used to establish linkages to water infiltration were discontinued. These measurements are taken throughout the growing season in producer⿿s fields and are laborious. Thus, we shifted to quantify the spatial variability between water isotopes and microbial activity, and to establish a covariance of these measurements that could lead us to identify how they are related to each other. We made significant progress in completing the laboratory analyses of previously collected soil samples from two of the three fields that were part of this experiment. As part of Objective 3, we used crop simulations of the U.S. Southern High Plains (SHP) dryland sorghum and cotton production, a profit and risk analysis based on the resulting climate-representative yield distributions were converted into corresponding profit distributions reflecting 2005⿿2019 Texas commodity prices and 2018 production costs. Profitability of the two crops was compared in terms of median profits and loss probability, through a stochastic dominance analysis that assumed a slightly risk-averse producer. During fiscal year 2020 collaborative research efforts resulted in modeling effects of temperature and humidity on cattle mortality in SHP feedlots. The results of a second collaborative effort focused on the simulated water balances of two major SHP soil types. Other collaborative research during the fiscal year simulated the effects of soil organic matter on soil water capacity and dryland cotton yields using the Decision Support System for Agrotechnology Transfer Crop Grow (DSSAT CROPGRO)-Cotton crop model. For Objective 4, our analysis of dust emission data from a field campaign sampling cropped and native range soil surfaces in five Southwestern states using a portable wind erosion instrument, i.e., Portable In-Situ Wind ERosion Lab (PI-SWERL) was accomplished during the first 4 weeks of telework. This data, including critical parameters of threshold wind speed, maximum dust emissivity, and supply limitations, which was disseminated to two teams of university scientists working on dust emission models using remotely sensed aerodynamic roughness estimates. Maximized telework precluded the travel to the study site (Sevilleta National Wildlife Refuge) to collect samplers in the shrubland plant community and post-fire re-installation of sampler masts in the grassland. Within this objective, as part of a multi-location ARS study of soil change, researchers are preparing, extracting and scheduling chemical analysis of anthropogenic radioisotopes to estimate decadal scale soil redistribution that may be causing the changes in soil properties in the last 7 decades. One of our scientists was selected as an expert in a scientific advisory panel of the National Academies of Science, Engineering, and Medicine by a court mandated to arbitrate a dispute between two governmental parties with responsibility to remediate Owens Dry Lake, at one time North America's largest single dust source. To accomplish Objective 5, there are different studies related to partitioning of evapotranspiration to water evaporation from soil and crop surfaces for dryland and irrigated cropping systems across different N fertilizer management strategies. For one of the studies, we established numerous groundwater and surface water sampling sites east of the SHP. Samples were collected each month for laboratory analysis and in- situ measurements of temperature and dissolved oxygen, and additional chemical data were obtained from the Texas Commission on Environmental Quality (TCEQ). In addition, we measured spring flow rates and water chemistry at Dickens Springs and at Silver Falls in Crosby County. A new stock pond (cattle tank) study at the Yellow House Ranch in Hockley County, Texas revealed that water quantity and quality vary seasonally and is influenced by rainfall and runoff in the watershed. We also have studies, as part of Objective 5, to improve the use of rainfall for crop production by quantifying each element of the water balance to maximize the amount of rainfall that can be stored in the soil and to minimize runoff. This analysis was done using a mechanistic model applied to a bare soil with no crop and for three rainfall scenarios (below average, average and above average) for two major soil types of the SHP (Amarillo and Pullman series). Results showed that for years with average and above average (wet) rainfall, only soils in the Pullman series could store water. However, in the Amarillo soils, storage could be enhanced using furrow dikes, minimum tillage along with cover crops that minimize evaporative losses of water from the soil surface. We continue to develop mechanistic models to quantify the process of rainfall storage in the soil. Within Objective 6, frequent samplings from several producer⿿s sites across the SHP are providing us with an opportunity to evaluate different management practices including a transition to no-tillage. For example, we identified 13 sites, representing more than 10,000 acres, through a producer will provide a comparison of different combinations of cover crops and no-tillage. Additionally, sampling every year since 2011 at five producer's fields in Lamb County under similar cotton-management enable us to quantify the effect of climate on the soil microbial community. Our frequent samplings showed decreases in the community during 2016, which was a very warm year. Subsequent samplings in 2017, 2018 and 2019 demonstrated a remarkable resilience of the soil microbial communities in these semiarid soils. Accomplishments 01 Dryland sorghum production may be a profitable alternative to dryland cotton production in the U.S. Southern High Plains. During 2012-2018 an average of 64% of planted cotton acres on the U.S. Southern High Plains (SHP) were not irrigated and that fraction may increase as the Ogallala aquifer continues to decline. Because of the region⿿s risky agricultural production conditions and increasing reliance on rainfall to maintain profitability, producers need to know which rainfed crops and management practices are best for the SHP summer climate and environment. To determine best practices for the region⿿s two leading rainfed crops ⿿ cotton and sorghum ⿿ an ARS scientist from Lubbock, Texas, used Texas Tech University Mesonet weather data and crop simulation models to determine the crop⿿s best planting dates and compare their profitability under rainfed conditions. The highest average cotton lint yields resulted from April 24 planting dates, while July 1 planting produced the highest average sorghum yields. Although sorghum is normally a secondary crop for SHP rainfed producers, these model simulations suggest that it may be more profitable and less risky than cotton under certain sorghum price conditions. As a result, SHP rainfed cotton farmers might consider planting sorghum, or combining cotton with sorghum production, to stay profitable without irrigation. 02 Spring discharge investigation reveals seasonal patterns of irrigation. In the late 19th century, many large cattle ranches were established in West Texas along the breaks at the eastern edge of the Llano Estacado. These ranches were located near spring-fed streams that provided a reliable supply of water in a region with otherwise limited water resources. Large-scale irrigation has altered hydrological conditions across the High Plains region, which has influenced the flow of springs along the eastern edge of the Llano Estacado. ARS scientists from Lubbock, Texas, obtained measurements of spring flow rates over a period of seven years. These measurements did not show an appreciable reduction of spring discharge associated with the depletion of the Ogallala aquifer, as might be expected. However, spring discharge was found to follow a seasonal pattern of declining flow during the summer growing season followed by a recovery starting in late fall and reaching maximum discharge during winter and early spring. This result suggests that irrigation of cropland on the high plains of the Llano Estacado can influence the flow of ephemeral streams in the ranchlands to the east of the Llano Estacado. These seasonal effects can reduce the amount of water available to cattle ranches located downstream of the Southern High Plains. 03 Pullman soils are suited for dryland production as they can store rainfall in years with average and above average rainfall. Dryland production continues to increase in the Texas High Plains (THP) due to a decline in irrigation-water from the Ogallala aquifer. A strategy to minimize the impact of the decline on crop yields across the region is to maximize the use of rainfall by reducing runoff and increasing storage of water in the soil. The end result from this transition to more dryland production is the increased dependency of crop yields on the amount of rainfall captured and stored in the soil profile. Scientists from Lubbock, Texas, used a simulation model to evaluate the daily water balance and the impact of a dry (7 inches), an average (18 inches) and a wet (26 inches) year of rainfall for two major soil types of the THP, Pullman in the north and Amarillo in the south. Results showed that for an average and wet year the Pullman soils can store water from the rainfall. However, this was not the case for the Amarillo soils. Nevertheless, management practices such as minimum tillage and ground cover residue can be used to enhance the capture of rainfall and assure adequate soil water to successfully grow crops. This has important implications for dryland production in the THP and shows the importance of minimizing evaporative losses of water from the soil by using residue covers, particularly in the southern region of the THP. 04 Biological indicators of soil health showed remarkable resilience after an extreme drought. Soil health and conservation initiatives agree that higher microbial abundance and activity are indicative of a healthier soil following the ⿿more-is-better⿝ model. Scientists from ARS in Lubbock, Texas, and Agriculture and Agri-Food Canada in Harrow, Ontario, assessed the effect of climate variability on different biological indicators of soil health (e.g., microbial community size and enzyme activities involved in nutrient cycling). The five-year study evaluated five sites under continuous cotton from the Texas High Plains semi-arid region. The sites differed in irrigation practices (drip, pivot and dryland), and soil textural class (e.g., from sandy loam to clay). Soil health indicators declined at all sites in response to decreased precipitation and increased temperatures from 2015 to 2016. However, as conditions improved, the evaluated indicators showed increasing trends within 1-2 years demonstrating a remarkable resilience. Our study highlights the need for implementing sustainable agricultural systems that optimize productivity, and conserve water to maintain soil health in a changing climate.

Impacts
(N/A)

Publications

Mauget, S.A., Marek, G.W., Adhikari, P., Leiker, G.R., Mahan, J.R., Payton, P.R., Ale, S. 2020. Optimizing dryland crop management to regional climate. Part I: U.S. southern high plains cotton production. Frontiers in Sustainable Food Systems. 3:120.
Masiokas, M.H., Cara, L., Villaba,, R., Pitte,, P., Luckman, B.H., Toum, E. , Christie, D.A., Le Quesne, C., Mauget, S.A. 2019. Streamflow variations across the Andes (18°-55°S) during the instrumental era. Hydrology and Earth System Sciences. 9:17879.
Perez-Guzman, L., Acosta Martinez, V., Phillips, L.A., Mauget, S.A. 2020. Resilience of the microbial communities of semi-arid agricultural soils during natural climatic variability events. Applied Soil Ecology. 149.
Lascano, R.J., Stout, J.E., Goebel, T.S., Gitz, D.C. 2019. A portable and mobile rainfall simulator. Open Journal of Soil Science. 9:207-218.
Bandari, K., West, C., Acosta Martinez, V. 2020. Assessing the role of interseeding alfalfa into grass on improving pasture soil health in semi- arid Texas High Plains. Applied Soil Ecology. 147.
Allen, D., Ajami, N., Bahreini, R., Biswas, P., Eviner, V., Johnson, S., Okin, G., Russell, A., Tyler, S., Van Pelt, R.S., Venkantrum, A., Wassell, R. 2020. Report of the national academies of science, engineering, and medicine owens lake scientific advisory panel. Proceedings of the National Academy of Sciences.
Allen, L.H., Kimball, B.A., Bunce, J.A., Toshimoto, M., Harazono, Y., Baker, J.T., Boote, K.J., White, J.W. 2020. Fluctuations of CO2 in Free- Air CO2 Enrichment (FACE) depress plant photosynthesis, growth, and yield. Agricultural and Forest Meteorology. 284.
Broadway, P.R., Mauget, S.A., Sanchez, N.C., Carroll, J.A. 2020. Correlation of ambient temperature with feedlot cattle morbidity and mortality in the Texas Panhandle. Frontiers in Veterinary Science. 7:413.
Gitz, D.C., Baker, J.T., Xin, Z., Lascano, R.J., Stout, J.E. 2019. Systematic error introduced into sorghum yield data: Does the multiseed (msd) trait increase sorghum seed yield? American Journal of Plant Sciences. 10:1503-1516.
Grace, J., Acosta Martinez, V., Rideout-Hazak, S., Stanko, R., Ortega, A., Wester, D. 2019. Soil microbial community size and composition changes along a tanglehead (Heteropogon contortus) gradient in a semiarid region. Applied Soil Ecology. 138:37-46.
Lascano, R.J., Leiker, G.R., Goebel, T.S., Mauget, S.A., Gitz, D.C. 2020. Water balance of two major soil types of the Texas High Plains: Implications for dryland crop production. Open Journal of Soil Science. 10:274-297.
Mauget, S.A., Kothari, K., Leiker, G.R., Emendack, Y., Xin, Z., Hayes, C.M. , Ale, S., Baumhardt, R.L. 2020. Optimizing dryland crop management to regional climate. Part II: U.S. Southern High Plains sorghum production. Frontiers in Sustainable Food Systems. 3:119.

Progress 10/01/18 to 09/30/19

Outputs
Progress Report Objectives (from AD-416): Obj 1: Quantify the environmental factors that affect the degree of crop drought stress. Sub-obj 1A Assess the effects of rising atmospheric CO2 concentration on crop coefficients used in deficit irrigation scheduling systems. Sub-obj 1B Relate seasonal plant stress and water use efficiency responses of crop plants to irrigation scheduling techniques using stable carbon isotope discrimination. Sub-obj 1C Identify active root areas under sub-surface irrigation to determine optimal cultivar for dryland management. Obj 2: Develop crop management strategies that enhance water use efficiency. Sub-obj 2A Quantify the effects of wind speed, tillage management, and irradiance on surface water evaporation. Sub-obj 2B Identify changes in microbial and chemical characteristics that may impact water availability and productivity in dryland production. Obj 3 Develop a framework of methods and models for quantifying and studying the risks associated with water from rainfall for dryland agriculture over the Southern High Plains and other dryland agricultural regions. Sub-obj 3A Evaluate the ability of current weather generator configurations to reproduce the distributional characteristics of Southern High Plains summer weather variability. Sub-obj 3B Run calibrated and validated cotton and sorghum crop models with both observed and stochastically generated weather inputs to generate simulated dryland yield outcomes. Sub-obj 3C Convert modeled yield outcomes generated with simulated weather data into net profit outcomes to form corresponding profit distributions for dryland cotton and sorghum production. Obj 4: Evaluate management practices that prevent soil degradation by soil erosion in semiarid cropping and rangeland systems. Sub-obj 4A Investigate soil redistribution & dust emissions from agro- ecosystems including rangelands & native plant communities under the stressors resulting from climate change. Sub-obj 4B Evaluate management systems in terms of multi-decadal erosion rates estimated from radioisotope inventories. Obj 5: Evaluate management practices to increase soil water availability and contribute to higher water and nutrient use efficiencies. Sub-obj 5A Partitioning of evapotranspiration to water evaporation from soil & crop surfaces for dryland & irrigated cropping systems across different N fertilizer management strategies. Sub-obj 5B Investigate changes in groundwater quantity & quality that may affect cropland production in semiarid & arid regions. Obj 6: Develop management practices that contribute to maintaining microbial diversity and functions needed to improve soil health, ensure ecosystem sustainability, and maintain crop productivity under a changing climate. Sub-obj 6A Compare the effects of different management practices in semiarid regions on soil health indicators including the microbial community size, diversity & functions. Sub-obj 6B Characterize the effects of climatic events on soil health & the effects of future climate change (CO2, temperature and rainfall) on agro-ecosystems by measuring root biomass, soil microbial diversity & soil organic matter pools. Approach (from AD-416): Sustainable agriculture, with emphasis on conservation of natural resources, is a challenge in the semiarid climate of the Southern High Plains (SHP). Of concern is developing cropping systems that cope with climate change, depletion of aquifers used for irrigation, and growing seasons characterized by frequent droughts and erratic rainfall. Climate change is expected to impose general global challenges but, clearly, solutions to these problems will be site specific. Within a framework to quantify and study the risks associated with dryland agriculture, we need sustainable agricultural systems that optimize productivity, conserve water, control soil erosion and improve soil health for agricultural production in semiarid regions and in a changing climate. We will continue long-term research that identifies management practices that impact water availability in dryland farming vs. lands in the Conservation Reserve Program. Our goal is to provide agricultural producers with tools to manage limited water resources in the semi-arid environment of the SHP. New technologies for exposing crops in the field to elevated levels of atmospheric CO2 concentration will be used to monitor hourly and daily whole canopy water use efficiency by simultaneously measuring the ratio of net CO2 assimilation to evapotranspiration. Optimum irrigation scheduling techniques will be determined from stable carbon isotope discrimination while optimal cultivars for dryland agriculture will be selected by identifying and comparing active rooting areas. This multifaceted research program will provide the knowledge base for optimizing the use of scarce water resources in arid and semi-arid regions where ground water resources are being depleted. For a second year, ARS scientists working in Lubbock, Texas, made significant progress to develop management strategies for regions of lower rainfall and of diminishing irrigation-water to improve water conservation and develop soil biological indices to evaluate soil health. Studies were completed to quantify environmental factors that affect the degree of crop drought stress. Two growing seasons studying the effects of elevated CO2 concentration interactions with periodic drought stress on peanut were completed and a manuscript is under preparation. Different solvent-extraction methods for a stable C isotope technique to extract oil from cottonseeds was tested and were equally efficient, a result that will be reported in a short communication. An extraction method for a small numbers of seeds using microscale Soxhlet extractors was developed and is being characterized. A new instrument to quantify root-water uptake of crop cultivars grown in dryland conditions was evaluated using a 0.3 m diameter polyvinyl chloride pots, with holes in the bottom to drain water and vertical strips of bolts, 5 cm apart to measure conductance. Given the rapid movement of water through the fritted clay, standard soil sampling techniques were not useful and thus a method was developed, whereby filter papers could be inserted, extracted and replaced with a new filter paper and thereby multiple samples of the soil water could be sealed in glass tubes and frozen for later analysis. This is information needed to evaluate what cultivars are more efficient in using rainwater under dryland conditions. Capital expenditures were made to modify an available structure for experiments requiring climate control. We continue to install heaters and partitions needed for the experiment, which is scheduled for winter months due to the requirement of high ambient vapor pressure deficits. This year, ample spring rain broke a multi-year drought and provided sufficient soil water to extract soil monoliths needed for the experiment. Extraction equipment was readied for monolith collection and the monolith shells modified to accommodate the required instrumentation. We continued our soil sampling measuring changes in soil microbial community that when coupled with stable isotopes of the rainwater infiltrating the soil could lead to understand mechanisms to increase soil water storage. The crop growth (CROPGRO) simulation applied to sorghum modeling and statistical evaluation of measured and simulated crop yields was conducted. Crop yield database containing modeled cotton (lint) and sorghum (grain) yields was completed. After calibration, based on four years of sorghum field trials, the Decision Support System for Agrotechnology Transfer (DSSAT) CERES-Sorghum model was used to simulate rainfed sorghum production at numerous Southern High Plains production sites during 2005⿿2016. These simulations were repeated under 32 management options to evaluate the effects of planting date, plant density, and nitrogen (N) application on crop yield. The resulting sorghum yields completed the yield database required for a 36-month study comparing dryland cotton and sorghum profitability. An associated manuscript has been submitted to Frontiers in Sustainable Food Systems. During FY 2019 data from 11 years of May- and June-planted irrigated variety trials conducted at Texas A&M AgriLife Research Center in Lubbock was used to study the effects of planting date on cotton lint yield and fiber quality. These results were reported on a manuscript submitted to Agriculture that was accepted for publication. During FY 2019 collaborative research efforts begun focusing on the effects of soil organic matter on soil water capacity and dryland cotton lint yields, ambient temperature and humidity effects on cattle mortality in Southern High Plains feedlots, and on an R-based analysis of cotton genetic sequences. Studies evaluating management practices that prevent soil erosion in semiarid cropping and rangeland systems were advanced. Dust emissivity data collected during a field campaign testing the soil surfaces of cropped fields and native plant communities were analyzed. Also, soil samples collected at the time of dust emissivity were analyzed for particle diameter distribution, and a manuscript with these results is being written. Horizontal mass flux data from climax black grama grasslands and nearby shrublands on the Sevilleta National Wildlife Refuge in New Mexico were collected and the data analyzed. The shrubland sampler mast array was removed and reinstalled to the pattern used by the National Wind Erosion Research Network (NWERN). The three plots in the grassland were removed in preparation for a controlled burn in April that was cancelled and rescheduled for the late summer to early fall of 2019. The grassland samplers will be reinstalled post-burn in a NWERN pattern. Equipment was constructed that will allow periodic removal and reinstallation of sampler masts used in the NWERN sites in Big Spring and other remote plots. Finally, work has begun to develop an instrument that measures the strength of soil crusts that resist shear forces present during wind events. Through a non-funded cooperative agreement with the Department of Chemistry at Northern Arizona University, more than 300 soil extracts were prepared for 239+240Pu quantification by Magnetic Sector Inductively Coupled Plasma / Mass Spectrometry (ICP/MS). This data will identify the boundaries of the region in which fallout from the Trinity Site detonation in July of 1945 would render the radio-isotopic technique models as they currently exist invalid. Other samples including sample splits previously counted for 137Cs inventory from Bushland, Texas and organic soils from Michigan and Florida are scheduled for Magnetic Sector ICP/MS quantification this summer. Soil samples were collected at research stations in Big Spring, Texas, Akron, Colorado, and Moccasin, Montana to investigate several soil properties and their change since 1947, when archived samples were collected. The 239+240Pu analysis will quantify changes attributable to soil redistribution since the sampling date. An existing rainfall simulator (RFS) to be transported with a commercial cargo trailer was modified by cutting out the floor under the RFS and by removing the axles and replacing them with bilateral wheel hubs. Additionally, a remote control trailer mover rated for 1500 kg was purchased. The final result was a portable and mobile RFS that can be moved to fields using a hitch and can be operated by 50 % less people, from 4 to 2. The trailer and RFS were built and a manuscript is in preparation. An engineering computer-aided design (CAD) program will provide a detailed construction and of parts needed to build the RFS. An ARS scientist will use the RFS to collect data on rainfall rates and amount on major soil types and subsequent runoff and infiltration. These results will be merged with the energy and water balance (ENWATBAL) model to evaluate the components of the water balance. To model management practices for water use efficiency, several inputs must be measured including rainwater infiltration, ponding and runoff. The mobile RFS was finished and we are currently testing and calibrating the system for deployment to fields across the Texas High Plains and New Mexico. Field data obtained with the RFS will be combined with laboratory measurement to measure saturated hydraulic conductivity, bulk density, and soil water retention curves on undisturbed soil samples. The plan is to create a library of measured soil hydraulic properties for the Pullman, Amarillo and Brownfield soil series. These data are required for simulation models, e.g., ENWATBAL and DSSAT-CERES that we use in our research. Studies to investigate changes in groundwater quantity and quality that may affect cropland production in arid regions are on schedule. To date, a total of 21 well sites located on the Southern High Plains were sampled over the last couple of years. Samples were collected, when weather permitted, from all sites every two weeks. Depth to water measurements were obtained using a commercial water level meter whenever the wells were not operating. When the wells were in operation, water samples were obtained from faucets on the well. If a well was off then pencil bailers were lowered into the well to obtain water samples, which were tested for pH and electrical conductance. In FY 2019, we expanded our study to include other sources of water such as rainfall, springs, and surface water sources such as streams and ponds. We continued our progress in the evaluation of different management, including drought tolerant crops/forages, that sustain microbial diversity and functions to improve soil health, ensure ecosystem productivity, and reduce irrigation-water from the Ogallala aquifer. The area office post-doc awarded to this project is evaluating data for several soil health indicators and functions collected over 5 years that experienced record high and low rainfall. Discussions from a joint meeting of producers with Texas Tech and ARS scientists at Lubbock indicated interest in applying manure in combination with conservation tillage practices for dryland cotton production. Their interest is to evaluate how this approach impacts soil health. The response of soil microbial community and their functions including soil productivity and nutrient cycling due to increases in CO2 levels using portable growth chambers continues to be evaluated. Accomplishments 01 Assay of multiple enzyme activities (EAs) in a soil sample as a new soil biology-health index. Current protocols used to measure EAs are time-consuming and each assay requires a soil sample. This limits routine measurements of EAs by commercial laboratories and their use for large-scale soil health assessments due to the associated high cost. To alleviate this problem, ARS scientists in Lubbock, Texas, and Morris, Minnesota, developed an assay to simultaneously measure multiple EAs on the same soil sample. This simplified protocol is adaptable for a wide range of applications to evaluate soil health for a variety of cropping systems options and soil types. This approach reduces time and minimizes chemical waste generated from assaying individual EAs on several soil samples. Our expectation is that a single EA value derived from this combined enzyme assay will contribute to the adoption of EAs for producer-oriented soil health assessments in commercial laboratories. Further, it will facilitate meta-analyses and our understanding of trends and thresholds related to biogeochemical cycling potential across regions at large spatial scales. 02 Alternative forages for livestock production increased soil health and drought tolerance. Scientists from Texas Tech University and USDA-ARS in Lubbock, Texas, previously found improvements in soil health indicators (e.g., microbial community, organic matter, and enzyme activities of nutrient cycling) with the introduction of Old World bluestem (OWB) grass for livestock-cotton production in the Southern High Plains. The system also reduced tillage and irrigation (36 %) compared to monoculture cotton. Soil health was further compared under other forages more drought tolerant than OWB, which included OWB- alfalfa, alfalfa, and native mixed-grass pastures. The OWB-alfalfa system offered suppression of pestiferous ants, desirable cattle productivity when grazed, eliminated fertilizer requirements due to N fixation and enhanced soil health indicators, i.e., greatest fungal and bacterial populations and their enzyme activities. The forage system with alfalfa can provide a desirable forage for producers in a semi- arid region with a declining irrigation-water supply. 03 Seed size and uniformity affect crop value and harvest efficiency. Uniform seed size leads to easier harvesting, cleaning, and processing. It has long been thought that increasing seed numbers in plants would increase crop yield. Molecular biologists and breeders seldom look closely at seed size and usually characterize seeds with qualitative terms such as small or large, or simply weigh a hundred seeds and measure the average weight. A scientist from ARS in Lubbock, Texas, developed a method to quantitatively measure the volume differences of thousands of seeds resulting from differences in development. We showed that this approach is capable of clearly revealing differences in grain development in two types of sorghum. This approach can be used to select for uniformity of seed size in germplasm improvement and to examine efficiency of seed cleaning operations. 04 Sustainable agriculture depends upon maintaining production while reducing or even eliminating dependence on non-renewable resources. Although, molecular biologists have developed plants with traits such as those associated with resistance to insect damage or herbicide resistance, no single gene has been identified that is associated with drought tolerance. Maintaining yield under drought stress is important because precipitation is seldom optimal in the southwestern U.S. and irrigation water resources are being depleted. Scientists from ARS, Lubbock, Texas, Texas Tech University, Tohoku University (Japan), and the Volcani Center (Israel) inserted a gene from tomatoes into cotton plants. Cotton plants altered with the tomato gene continued to use sunlight to function under conditions where the normal plants had stopped functioning. Over the course of a preliminary small-scale pilot study, cotton yield was increased by 80%. These results suggested that this approach could result in traits to sustain or even improve cotton yield under mild droughty conditions typical of the southwestern U.S. 05 Planting date effects on cotton lint yield and fiber quality in the U.S. Southern High Plains. The U.S. Southern High Plains (SHP) is a leading U.S. cotton production region, but its high altitude and short growing season can reduce yields and fiber quality. To study the effects of SHP cotton planting dates in a field setting, ARS researchers at Lubbock, Texas, evaluated planting date effects on lint yield and fiber quality in 11 years of May- and June- planted irrigated variety trials. May planting increased lint yields in 8 of 10 years that comparisons could be made, and improved fiber fineness and maturity in 7 of 11 years. These effects, and analysis of SHP temperature data, show that late- April to early-May planting dates may increase lint yield and improve fiber quality. Although this practice may be best for the cool SHP summer growing environment it may also require high-vigor seed and pre- planting irrigation. 06 Irrigation system better suited to capture more rainfall in the Texas High Plains. In the Texas High Plains, the majority of the soils in cultivation are in three soil series: Olton, Pullman, and Amarillo, and soils tend to be sandier in the southern region and finer-textured soils more common in the northern region. The distribution of dryland and irrigated crop production is about 60% dryland and 40% irrigated. However, the amount of dryland production continues to increase every year due to the decline of the aquifer⿿s water table. Regardless of the cropping system in place the capture and use of rainfall is imperative. Further, what irrigation system (sprinkler vs. buried drip) makes better use of rainfall? Our hypothesis was that for the rainfall frequency and distribution of this region, crops would use more rain when irrigated with a sprinkler system compared to a buried drip. ARS scientists in Lubbock, Texas, tested the hypothesis using stable isotopes of water, given that rain- and irrigation-water have different isotopic signatures, and our hypothesis was shown to be correct. This result is explained by how rainfall frequency and amount affects the root distribution in the soil profile. For example, a sprinkler system promotes surface roots; whereas, a buried drip system tends to concentrate roots around the buried emitter. Thus a crop irrigated with a sprinkler system will likely have a root distribution adept to use water from rain events of 10-15 mm and a crop irrigated with a buried drip will not have the roots to use this water and as a result a larger proportion would be lost to evaporation. 07 Measurement of crop transpiration (T) under field conditions. In first analysis, the primary objective of irrigation is to replace the quantity of water transpired (T) by the crop. This is a simple premise but it is complicated by the fact that the measurement of crop T is difficult to obtain and as result measurements are replaced by calculations of evapotranspiration (ET), which requires estimates of soil water evaporation (E). For this purpose engineers have introduced a myriad of methods to calculate ET and of coefficients to empirically estimate T and E. Conversely, a null method to measure T was introduced by a Japanese scientist in the early 1980⿿s known as the stem heat balance method (SHBM). Scientists from ARS in Lubbock, Texas, evaluated a commercial version of the SHBM on cotton plants and we compared these measurements to values of cotton T measured with portable growth chambers on the same plants. Our results showed that the two values of cotton T measured with the SHBM and the chambers were statistically the same. The commercial sensor to measure cotton T provides a practical method that can be used to manage the irrigation of a crop. 08 Well sampling and salinity profile investigations. Scientists from ARS in Lubbock, Texas, samplings from groundwater at several locations across the Texas High Plains showed that while wells are active, the water quality can change; however, it is not always increasing in salinity. Salinity profile measurements have shown that, in most cases, groundwater is more saline towards the bottom of a well. As a result, when a well becomes active the more saline water is mixed from below into the upper portion of the profile and the entire water column becomes more uniform and generally more saline. With regard to the rainfall study, preliminary results suggest that there is a surprisingly weak statistical correlation between rainfall chemistry and atmospheric conditions, such as wind speed or direction. Further analysis of rainfall samples did, however, show a significant inverse relationship between salinity and the amount of rainfall collected in the rain gauge.

Impacts
(N/A)

Publications

Bhandari, K., West, C.P., Acosta Martinez, V., Cotton, J.E., Cano, A. 2018. Soil health indicators as affected by diverse forage species and mixtures in semi-arid pastures. Applied Soil Ecology. 132:179-186.
Mauget, S.A., Ulloa, M., Dever, J. 2019. Planting date effects on cotton lint yield and fiber quality in the U.S. Southern High Plains. Agriculture. 9:82.
Lascano, R.J., Baker, J.T., Payton, P.R., Gitz, D.C., Mahan, J.R., Goebel, T. 2018. Measurement of cotton transpiration. Agricultural Sciences.
Gitz, D.C., Baker, J.T., Payton, P.R., Xin, Z., Lascano, R.J. 2018. Analysis of grain size distribution through image analysis. American Journal of Plant Sciences. 9:2339-2346.
Stout, J.E. 2019. On the dissolved mineral content of rainfall samples on the Llano Estacado. Journal of Hydrometeorology. 20:1235.
Acosta Martinez, V., Perez-Guzman, L., Johnson, J.M. 2019. Simultaneous determination of ÿ-glucosidase, ÿ-glucosaminidase, acid phosphomonoesterase, and arylsulfatase in a soil sample for a biogeochemical cycling index. Applied Soil Ecology. 142:72-80.

Progress 10/01/17 to 09/30/18

Outputs
Progress Report Objectives (from AD-416): Obj 1: Quantify the environmental factors that affect the degree of crop drought stress. Sub-obj 1A Assess the effects of rising atmospheric CO2 concentration on crop coefficients used in deficit irrigation scheduling systems. Sub-obj 1B Relate seasonal plant stress and water use efficiency responses of crop plants to irrigation scheduling techniques using stable carbon isotope discrimination. Sub-obj 1C Identify active root areas under sub-surface irrigation to determine optimal cultivar for dryland management. Obj 2: Develop crop management strategies that enhance water use efficiency. Sub-obj 2A Quantify the effects of wind speed, tillage management, and irradiance on surface water evaporation. Sub-obj 2B Identify changes in microbial and chemical characteristics that may impact water availability and productivity in dryland production. Obj 3 Develop a framework of methods and models for quantifying and studying the risks associated with water from rainfall for dryland agriculture over the Southern High Plains and other dryland agricultural regions. Sub-obj 3A Evaluate the ability of current weather generator configurations to reproduce the distributional characteristics of Southern High Plains summer weather variability. Sub-obj 3B Run calibrated and validated cotton and sorghum crop models with both observed and stochastically generated weather inputs to generate simulated dryland yield outcomes. Sub-obj 3C Convert modeled yield outcomes generated with simulated weather data into net profit outcomes to form corresponding profit distributions for dryland cotton and sorghum production. Obj 4: Evaluate management practices that prevent soil degradation by soil erosion in semiarid cropping and rangeland systems. Sub-obj 4A Investigate soil redistribution & dust emissions from agro- ecosystems including rangelands & native plant communities under the stressors resulting from climate change. Sub-obj 4B Evaluate management systems in terms of multi-decadal erosion rates estimated from radioisotope inventories. Obj 5: Evaluate management practices to increase soil water availability and contribute to higher water and nutrient use efficiencies. Sub-obj 5A Partitioning of evapotranspiration to water evaporation from soil & crop surfaces for dryland & irrigated cropping systems across different N fertilizer management strategies. Sub-obj 5B Investigate changes in groundwater quantity & quality that may affect cropland production in semiarid & arid regions. Obj 6: Develop management practices that contribute to maintaining microbial diversity and functions needed to improve soil health, ensure ecosystem sustainability, and maintain crop productivity under a changing climate. Sub-obj 6A Compare the effects of different management practices in semiarid regions on soil health indicators including the microbial community size, diversity & functions. Sub-obj 6B Characterize the effects of climatic events on soil health & the effects of future climate change (CO2, temperature and rainfall) on agro-ecosystems by measuring root biomass, soil microbial diversity & soil organic matter pools. Approach (from AD-416): Sustainable agriculture, with emphasis on conservation of natural resources, is a challenge in the semiarid climate of the Southern High Plains (SHP). Of concern is developing cropping systems that cope with climate change, depletion of aquifers used for irrigation, and growing seasons characterized by frequent droughts and erratic rainfall. Climate change is expected to impose general global challenges but, clearly, solutions to these problems will be site specific. Within a framework to quantify and study the risks associated with dryland agriculture, we need sustainable agricultural systems that optimize productivity, conserve water, control soil erosion and improve soil health for agricultural production in semiarid regions and in a changing climate. We will continue long-term research that identifies management practices that impact water availability in dryland farming vs. lands in the Conservation Reserve Program. Our goal is to provide agricultural producers with tools to manage limited water resources in the semi-arid environment of the SHP. New technologies for exposing crops in the field to elevated levels of atmospheric CO2 concentration will be used to monitor hourly and daily whole canopy water use efficiency by simultaneously measuring the ratio of net CO2 assimilation to evapotranspiration. Optimum irrigation scheduling techniques will be determined from stable carbon isotope discrimination while optimal cultivars for dryland agriculture will be selected by identifying and comparing active rooting areas. This multifaceted research program will provide the knowledge base for optimizing the use of scarce water resources in arid and semi-arid regions where ground water resources are being depleted. In September 2017, the objectives and milestones of the research project 3096-12610-001-00D, entitled Improving the Productivity and Climatic Resilience of Agricultural Production Systems in Semiarid and Arid Ecosystems were added to this project. As the impacts of climate variability become more intense, plant breeders need simple tools to screen for traits that may result in higher water use efficiency, i.e., more crop yield with less water. Within this first year of our plan, we explored whether seasonal water use efficiency could be assessed by analyzing oil extracted from cotton seeds at harvest-time (Sub-objective 1B). Standard American Oil Chemist Society methods of seed oil extraction were compared to modified methods that use less harmful solvents for oil extraction. We are currently scaling these methods down to a micro-scale and comparing these to other extraction methods to ensure there is no effect on subsequent analyses. Current field work consisted of growing several cotton cultivars with release dates spanning a century under controlled irrigation conditions to ensure material is on hand for analyses of trends in water use efficiency as measured by stable carbon isotope analysis. A new tool to quantify root-water uptake on cultivars to be grown under dryland conditions was evaluated (Sub-objective 5B). A prototype sensor that measures soil water content using a novel circular design was tested using a fritted clay material that has a wide range of soil water content (0 to 55 % by volume). A 12�inch diameter PVC pipe was cut and used as a pot. Holes were drilled into the bottom to drain water, and a stainless steel was placed in vertical strips 5-cm apart starting from the bottom. Each strip of 5 bolts had an identical vertical strip on the opposite side of the pot making 3 sets of conductivity meters at 5 different heights. Each bolt can be tested for conductance and thus create a 3- dimensional map of conductivity across the depth of the pot. A computer fitted with a special running board and relay modules that power the voltage sent to the individual conductance cells was used to run the program and measure the conductivity across all bolts. This setup of a pot, computer/sensor, and program will be tested for performance using increasing volumes of salt water to detect the movement of the salty water through the fritted clay. Once the movement of salt water into the fritted clay profile is demonstrated, a cotton plant will be planted and allowed to develop to the 1st square. A new solution of salt water will be prepared with a source that is isotopically enriched compared to the tap water and plant samples will be taken to determine if the cotton plant is using the new water substituting for rainwater. This is essential information needed to evaluate what cultivars are more efficient in using rainfall under dryland conditions. An important component of water use efficiency is to minimize soil water evaporation as affected by management practices (Sub-objective 3A). For this purpose we designed experiments on a wind tunnel to evaluate the effects of wind and tillage on evaporation. We purchased materials and equipment to maintain a constant air temperature and high vapor pressure deficit for a 15-m wind tunnel with 4 weighing lysimeters to measure evapotranspiration. The monolith shells and extractor were fabricated and are ready for monolith extraction. The region is currently in a state of extreme drought and the soils are too dry and hard that prevent us from obtaining hydrologically intact soil monoliths. The project will proceed with installation of climate control equipment and testing of the system. Furthermore, quantifying the partitioning of water evaporation from the soil and crop to increase crop yield while minimizing the loss of water from the soil is critical in cropping systems. Given the loss of a scientist in our unit we modified our research related to the partitioning of evapotranspiration for dryland and irrigated cropping systems. We are currently using an energy water balance simulation model developed by a scientist in the unit (Objective 3). An important input to this model is the intensity and duration of rainfall events and their impact on infiltration and runoff. One way to obtain these data is by using a rain simulator. To expedite and facilitate the transport of the rain simulator to the field was to attach the simulator to the cargo trailer, which was modified by cutting out the floor under the rain simulator and removing the axles and replacing them with axle-less wheel hubs. Additionally, a remote control trailer mover rated for 3,300 lbs was purchased. In the end we will have a portable rain simulator that can be pulled using a truck-hitch to field sites of interest and can be operated as remote controlled rain simulator by 1�2 people rather than 3�4. Other input soils data for the model are the soil hydraulic properties of the major soil series on the Texas High Plains. For this purpose, equipment was set up to make measurements on soil cores sampled from Brownfield and Amarillo, Texas soil series. These measurements include infiltration, soil water holding capacity, soil water retention curve and saturated hydraulic conductivity. Simulation models were used to evaluate risk assessment associated from dryland cropping systems across the semiarid Texas High Plains (Objective 3). For publishable results, it is important to use correct historical weather input data. Data sets were subjected to quality control tests. Weather input (5 and 15 minute) data of air temperature, precipitation, radiation, and wind for 21 West Texas Mesonet stations during the 2005�2017 period were averaged or summed into daily averages or totals. Statistical analyses of these data sets are underway using several computer models. The CROPGRO-Cotton model was run using weather inputs from the 21 West Texas Mesonet stations over an 11 year-period, and repeated under 32 management options. A journal paper describing this work was submitted for publication. Further, these results will be reported at the August 2018 Cropping Systems Research Laboratory Field Day, the December 2018 American Geophysical Union meeting, and the January 2019 Beltwide Cotton Meeting. The cotton lint yield and soil water content data that were provided by a Bushland, Texas ARS collaborator were evaluated and used to calibrate and initialize the DSSAT CROPGRO-Cotton and CROPGRO-Sorghum models. An associated paper was submitted giving estimates of dryland cotton lint yield variation and profit risk under a range of management options. Another element of our research project is to evaluate management practices that diminish soil erosion in cropping and rangeland systems (Objective 4). Multiple natural and agricultural surfaces at 25 different locations in Texas, New Mexico, Arizona, Colorado, and Utah were tested for respirable dust emissions using a portable in-situ wind erosion laboratory (PI-SWERL). Data were analyzed and summarized, and preliminary results were presented at the 10th International Conference on Aeolian Research in Bordeaux, France 25�29 June 2018 and at the 2018 Soil and Water Conservation Society Annual International Conference. Results indicated that many dust emission models overestimate emission by failure to consider surface crusting and that the differences between the emission rates from a crusted surface and a disturbed surface are often greater than an order of magnitude. Access to sample processing facilities has been unavailable up until autumn, 2018. However, previously collected samples were prepared and reagents acquired for analysis which is anticipated in October and November 2018. Reference locations will be sampled during the early spring of 2019. Samples from cropped lands will be collected in late spring of 2019. We continue to sample several wells across the Texas High Plains to evaluate changes in groundwater quantity and quality that may affect future dryland cropland production (Sub-objective 5B). In addition to our sampling regime, we are evaluating changes in salinity with depth inside each sampled well. We purchased a depth-to-water meter that has a probe to measure salinity as well. This will allow us to measure changes in salinity with depth, creating a profile for each sampled well. These profiles will then be compared from October to March to quantify if the salinity of each well is changing over time. Changes in soil microbial and chemical properties are indicators of productivity under dryland conditions (Objective 6). We began our soil sampling and installed neutron probes to measure soil water content, and rainfall on Conservation Reserve Program and dryland sites designated for this experiment. Our aim is to establish linkages of the microbial component that is essential to improve soil water holding capacity and productivity. We also continue to collect soil samples in several producer sites to evaluate changes in soil microbial communities that could be related to soil water conservation under the current climate variability. These soil samples were collected starting in 2011, when a record drought/heat wave occurred on the Texas High Plains. Further, we are also evaluating soil microbial data as affected by different management scenarios between 2015�2017. We are currently experiencing another drought and with our sampling scenario we have an opportunity to test the microbial response to climate variability under semiarid conditions. Scientists contribute to two big databases. One scientist is a member of the steering committee for the USDA-ARS Nutrient Use and Outcome database (NUOnet). Another scientist leads the Soil Biology Group comprised of 15 ARS scientists within the Greenhouse Gas Reduction through Agricultural Carbon Enhancement network. Accomplishments 01 Early planted rain-fed cotton yields more lint. As the Ogallala Aquifer levels decline, cotton producers on the Southern High Plains (SHP) need information on management practices that maximize crop yields and profits without irrigation. However, many of the potential combinations of management practices have not been investigated. Therefore, ARS scientists at Lubbock, Texas used a crop model driven by weather inputs from 21 west Texas Mesonet stations (2005�2016) and 32 combinations of planting dates, fertilizer levels, and seeding rates. Earlier planting dates had the greatest positive yield effect, with the lint yields increasing by 145 pounds per acre when planted on May 15th compared to June 5th. Lower plant densities also had a positive effect on profits. These crop simulations suggest planting on or before May 15 at a low plant density should maximize profitability and minimize loss on the SHP. 02 Characterization of a sugar cane aphid resistant sorghum. As irrigation-water is depleted, producers over the Ogallala Aquifer need access to drought tolerant crops, like sorghum, which can be grown under rain-fed conditions. However, profits of sorghum production are low compared to other crops. Also, controlling problems created by the new pest, sugar cane aphid, force growers to use insecticides, increasing the costs of crop production and lowering profits. ARS scientists from Lubbock, Texas characterized a mutant sorghum that has thick, narrow leaves, which showed resistance to the aphid and was drought tolerant. Incorporation of this trait into breeding programs could result in sorghum lines with greater drought and resistance to sugar cane aphid, which should lower production cost and increase profitability. 03 A framework to understand seasonal water fluctuations in the Ogallala Aquifer. On the Texas High Plains, groundwater pumping for irrigation has led to a significant depletion of the resources. As the volume of groundwater decreases, farmers need a better understanding of seasonal changes in groundwater availability and pumping rates to manage their withdrawals over the growing season. Water levels are generally observed to decline during the growing season and gradually recover when irrigation wells are switched off. However, these changes in depth to groundwater are difficult to compare and interpret. In an attempt to better understand this process, a theoretical framework was developed by ARS scientists from Lubbock, Texas and scientists from Texas Tech University. The resulting curves can be readily interpreted and compared to provide insight into seasonal irrigation patterns. Such information will provide irrigators a better estimate of groundwater availability especially later in the growing season. 04 Enhanced water use efficiency in peanuts. Carbon dioxide levels in the air have increased over the past half century. However, the effects of this increased carbon dioxide on crops is not fully understood. Therefore, ARS scientists from Lubbock, Texas examined the response of peanuts to increased carbon dioxide levels in the air under field conditions using special chambers. We discovered that the numbers of tiny pores (stomata) in peanut leaves decreased at higher carbon dioxide. Because these tiny pores also transport water out of leaves, these results suggest a mechanism where peanuts will exhibit greater water use efficiency at higher carbon dioxide levels. These results are of interest to plant physiologists, agronomists and crop breeders to better understand how crop plants can adapt to climate change. 05 Analysis of air temperatures indicate that the summer climate of the U. S. Midwestern Corn Belt has not changed. There are concerns that increases in atmospheric carbon dioxide will increase air temperatures. However, it is not well understood how changes in summer air temperatures will affect crop production in various regions of the United States. Therefore, ARS scientists at Lubbock, Texas analyzed trends in mean summer maximum and minimum temperatures from 1895 to 2015 for the important U.S. crop growing regions. Warming trends in summer minimum temperatures were found over almost all of the U.S. and increasing summer maximum temperatures were found in the west and northeast. However, no significant increases in summer temperatures were found from 1970 to 2015 for the key crop production region of the Midwestern Corn Belt. This research shows that the summer temperatures of the important agricultural region of the Midwestern Corn Belt have been stable in recent decades. 06 Analyses of multiple soil enzymes in one sample provides a new index of soil health. Farmers are interested in how cropping practices promote soil health or degrade soils. Producers need simple soil health tools to assist their selection of sustainable soil management practices. However, simple measures of soil health have been difficult to develop. Although enzyme activities are sensitive to management and represent measures of soil functions, the current protocols are time-consuming because each enzyme is measured separately. Therefore, ARS scientists in Lubbock, Texas and Minnesota developed an assay of multiple enzyme activities on the same soil sample, providing a protocol adaptable to many climatic zones and cropping systems. This method provides an index related to soil health. Our expectation is that the new assay will enable producers and land owners to assess soil health and adopt cropping practices that increase soil health. 07 Surface crusting affects the extent of soil movement by wind. Wind erosion can cause considerable damage to cropland and natural ecosystems in arid and semi-arid regions. However, the factors that affect the extent of soil erosion by wind are poorly understood. It is well established that soil texture affects wind erosion; however models using primarily soil texture as a variable tend to overestimate actual rates of soil movement by wind. Therefore, ARS scientists at Lubbock, Texas investigated the effects of soil surface crusting on wind erosion, using a portable wind erosion unit. These results confirmed the importance of surface crusting in sediment movement by wind, and will help refine wind erosion models and guide conservation management practices. 08 Wind erosion of soils in arid grassland occurs and is worst in shrubby ecosystems. Arid grasslands and shrubby ecosystems are dominant land types in the Southwestern United States and other arid regions world- wide. These regions tend to be characterized by relatively high wind velocities. However, estimates of soil or sediment movement by wind are not fully developed. ARS scientists at Lubbock, Texas measured sediment transport at locations in the Sevilleta National Wildlife Refuge in central New Mexico. Results revealed greater sediment transport rates in shrub communities than in desert grasslands; however, transport also occurred in desert perennial grasslands. These results dispute the widely held belief that soils under arid perennial grasslands were not transported by wind.

Impacts
(N/A)

Publications

Lascano, R.J., Baumhardt, R.L., Goebel, T.S., Baker, J.T., Gitz, D.C. 2017. Irrigation termination date and amount on cotton lint yield and fiber quality. Open Journal of Soil Science. 7(9):216-234. doi:10.4236/ojss.2017. 79016.
Li, C., Fultz, L.M., Moore-Kucera, J., Acosta Martinez, V., Kakarla, M., Weindorf, D. 2018. Soil microbial community restoration in conservation reserve program semi-arid grasslands. Soil Biology and Biochemistry. 118:166-177.
Qian, F., Jerolmack, D., Lancaster, N., Nickolich, G., Reverdy, P., Roberts, S., Shipley, T., Van Pelt, R.S., Zoebeck, T.M., Koditschek, D.E. 2017. Ground robotic measurement of aeolian processes. Aeolian Research. 27:1-11.
Olsen, S.C., Boggiatto, P.M., Vrentas, C.E. 2017. Inactivation of virulent Brucella species in culture and animal samples. Applied Biosafety. 22(4) :145-151.
Cano, A.M., Nunez, A., Acosta Martinez, V., Schipanski, M., Ghimire, R., Rice, C., West, C. 2018. Current knowledge and future research directions to link soil health and water conservation in the Ogallala Aquifer region. Geoderma. 328:109-118.
Acosta Martinez, V., Cano, A.M., Johnson, J.M. 2017. An approach to determine multiple enzyme activities in the same soil sample for soil health-biogeochemical indexes. Applied Soil Ecology. 126:121-128.
Goebel, T.S., Stout, J.E., Lascano, R.J. 2018. Seasonal changes in water quality of the lower Ogallala Aquifer. Texas Water Journal. 9:69-81.
Gitz, D.C., Liu Gitz, L., Xin, Z., Baker, J.T., Payton, P.R., Lascano, R.J. 2017. Description of a novel allelic �thick leafed� mutant of sorghum. American Journal of Plant Sciences. 8:2956-2965.