Source: TEXAS A&M UNIVERSITY submitted to NRP
INCREASING WATER USE EFFICIENCY FOR CROP PRODUCTION: AN APPROACH OF SOIL-PLANT WATER RELATIONS
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
COMPLETE
Funding Source
HATCH
Reporting Frequency
Annual
Accession No.
1002534
Grant No.
(N/A)
Cumulative Award Amt.
(N/A)
Proposal No.
(N/A)
Multistate No.
(N/A)
Project Start Date
Feb 3, 2014
Project End Date
Jan 31, 2019
Grant Year
(N/A)
Program Code
[(N/A)]- (N/A)
Recipient Organization
TEXAS A&M UNIVERSITY
750 AGRONOMY RD STE 2701
COLLEGE STATION,TX 77843-0001
Performing Department
Uvalde-TAMU Agr Res & Ext Cntr
Non Technical Summary
The 50-year projections of statewide water supply and demand by the Texas Water Development Board indicate a steady increased demand and steady declining water supply from 2010 to 2060. As agriculture is the biggest consumptive user of fresh water (accounting for 80-90% of national water use), the society naturally expects the scientific community to provide solutions and suggestions for improving crop production while preventing excessive ground water consumption for irrigation. The aim of this project is to identify opportunities for saving irrigation water through studying soils and crop physiological activities of row cropsin the Wintergarden region of southern Texas.We plan to collect field-scale information of crop growth characteristics and relate this to models of crop evapotranspiration and growth.Our hypothesis is that there is still room for additional irrigation water saving without sacrificing the profits from crop production. This could be brought about through adopting various managemnt strategies, including the use of crop varieties with deeper root growth, more efficient canopy architecture, conservation tillage and deficit irrigation, etc. We hope to quantify how much water can be saved through changes in crop management. As our research will be conducted at the field scale, the results and findings will have significant impact on sustainable irrigation water use by regional growers.
Animal Health Component
70%
Research Effort Categories
Basic
20%
Applied
70%
Developmental
10%
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
1020210107025%
2031510102030%
1111719106030%
2051549108115%
Knowledge Area
102 - Soil, Plant, Water, Nutrient Relationships; 111 - Conservation and Efficient Use of Water; 205 - Plant Management Systems; 203 - Plant Biological Efficiency and Abiotic Stresses Affecting Plants;

Subject Of Investigation
1510 - Corn; 1549 - Wheat, general/other; 1719 - Cotton, other; 0210 - Water resources;

Field Of Science
1060 - Biology (whole systems); 1070 - Ecology; 1081 - Breeding; 1020 - Physiology;
Goals / Objectives
Identify crop traits for improving crop water use efficiency and drought stress tolerance. This will allow a better understanding of the agronomic values of crop traits that manifest themselves under field conditions.Predict crop water use and evapotranspiration under particular soil, climate and management scenarios. One major outcome from this objective is a robust and accurate estimation of crop water use through combined use of and integrating various methods for quantifying soil-plant system water flow.Apply and develop decision-making tools for optimal management of crop water use. This involves knowledge integration and technology development for helping growers to make optimal decisions in irrigation management and crop production to cope with shortage of water and climate change.
Project Methods
The research work described in this project will be carried out under typical growing conditions of major row crops (corn, cotton and wheat) in the Wintergarden region of southern Texas. As shortage of water is the major factor limiting crop production in this region, irrigation management under different tillage conditions using different crop varieties will be the main focus in the project. The methods of research include observation, measurement, survey and modeling of crop physiological characteristics related to crop water use, growth and development. The main research efforts will be devoted to the collection of data of physiological processes (such as root growth and leaf photosynthesis and transpiration), as well as applying and developing models for integrating soil-plant processes to accurately predict crop water use and growth/development.The efforts of this project also include communications with regional growers/farmers to identify the relevant research problems and to address the problems by applying the scientific concepts due to this project.For evaluation purposes, the following key progress achievements may be considered:(1) Relate and link crop root/shoot characteristics (such as root growth and stomatal function) with crop growth to maximize harvest index.(2) Evaluate and validate ecophysiological models of crop water use against field plot-scale measurement of transpiration or evapotranspiration.(3) Assemble and integrate prior knowledge of crop growth and the data collected in this project for realistic prediction of cropping system productivity in the Wintergarden region.

Progress 02/03/14 to 01/31/19

Outputs
Target Audience:During this reporting period, Xuejun Dong and his group members reached differentgroups of audience, including students, farmers, professional scientists, local business managers, etc., and delivered numerouspresentations to crop/soil researchers, graduate students and/or the general public in regional and national/international conferences. The group mentored 4 undergraduate student workers, 5 graduate students (with one graduated MS student fully supported by the lab). We provided assistance and training/outreach to 12 local farmers, one officer of the Uvalde Underground Water ConservationDistrict. The groupmembers delivered 5 talks to educational field days, and 13 presentations to regional, national and international professional conferences. PI Dong deliverd 3 formal lecturesin class-room settings to professionals and graduate students. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?FromSeptember 2013 to January 2019, the Dong's group has trained a number of technicians, postodoc researchers (including visiting professors), and students.Research Assistant Beth Speer developed new skills inusing sap flow gauges to measure transpirationfrom individual plants. Reseach Assistant Angela Jones was trained to use the advanced mini-rhizotron technique to take plant root images and analize the resultant data. Research Asistant Shane Sieckenius developed skiils inusingground penetrating radar facility to remotely detectbelowground features, especially plantroots. Postdoc researcher Xiuwei Liu, while working at Dong's lab,developed skills both in ground penetratingradar technology and leaf alkane composition quantification using isotopic methods. Four visiting professors, Yongjiang Zhang, Jianchu Shi, Bin Peng and Gongneng Feng,participated in various field-based research projects and made significant contributions indata analysis and writing ofjournal articles. Graduate student Rahul Raman was trained to characterize leaf and canpoytraits of corn and sorghum genotypes for improved water use efficiency. The groupalso provided opportunities for fourundergraduate students to learnfield and lab procedures in agronomy research. How have the results been disseminated to communities of interest?The research results were summarized as oral/poster presentations in various professional conferences, online stories, as well as peer-reviewed journal publications. Each yearin past five years, the groupmembersparticipated inmore than three major conferences. Theyalso interacted with local farmers and entrepreneurs as well as local ground water district officers to disseminate reseach findings and look for new opportunities for forming partnership to enhance the group's research and extension effectiveness. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? (a) Using field measured data of stomatal conductance, we showedthat cotton variety DP1044 shut down its water use earlier than PHY499 in late season, leading to increased water use efficiency in the former. Further study showed that, compared with PHY499, stomatal conductance of DP1044 was more responsive to severe drought, which was accompanied by increased leaf water use efficiency. On the other hand, PHY499 responded to the increased water availability by increasing leaf and root growth, as well as stand water consumption. (b) Bystudying leaf wax isotopes of winter wheat varieties in contrasting environments, we found that compound-specific alkane isotopes can be used as precision predictors of water use efficiency and grain yield, which could help to expedite the process of crop breeding for improved water use efficiency in wheat as well as potentially with other agricultural crops. The main impact this finding has to plant physiology research community is to challenge the long-held view that the bulk leaf carbon isotopes are perhaps best indicators of integrated leaf water use efficiency in plants. More importantly, as the biosynthesis of particular alkane molecules are controlled by far fewer number of genes than do the various carbon molecules making up the bulk leaf, our finding is pointing to a new direction of looking for specific precision molecules for indicating WUE, thus has the hope of speeding up the breeding-based crop improvement process under water-limited conditions. (c) We developed a ground-based phenotyping cart and applied it for detecting leaf rust infection rate in winter wheat remotely. we found that Normalized Difference Red-Edge (NDRE) was better than Normalized Difference Vegetation Index (NDVI) in predicting leaf rust infection rate in winter wheat and the relationship was strongest during the flowering stage. In addition, in the jointing stage, our model also had considerable sensitivity. Two aspects are important in terms of impact: (a) our finding may help breeders rapidly detect leaf rust infection rate in leaf population (not just flag leaves) for a large number of genotypes, provided suitable sensors are used with UAS (Unmanned Aerial Systems).(b) The sensitivity of NDRE in indicating leaf rust development in early growth stages of wheat may be of value for farmers to prescribe a timely chemical control of leaf rust in winter wheat. (d) In collaboration with plant physiologist John Butnor at USDA Forest Service, as well as utilizing the multi-location trials within Texas A&M AgriLife Research, we developed a method to measure crop fine roots using ground penetrating radar (GPR) system. To our best knowledge, this was the first report demonstrating that GPR can measure fine root characteristics at a bulk soil level. Our further research indicated an improved prediction of root biomass of winter wheat under field conditions using a 2.6 GHz antenna, as compared with a 1.6 GHz antenna. These findings support the use of GPR technology as a vital component of crop root phenotyping studies in the future. (e) We developed computer programs (R and Minitab) for automated data processing to extract root distribution parameters of field crops using measured root length density data. Our root data from multiple years and across multiple locations allowed us to test current hypotheses regarding plant root economic spectrum and global root patterns across contrasting environments. We were surprised to note that two Kansas wheat varieties displayed significantly deeper roots compared with selected ten varieties that have adapted to the Southern Great Plains region in past decades. This unexpected finding was discussed in detail in our 2019 paper (J. Agron. Crop Sci.) and has implications for future breeding research in winter wheat. (f) Since September 2013, our ecophysiology research on multiple row crops (corn, cotton, sesame, sorghum, and wheat) generated the potential annual water savings worth of $2.8 million in the Wintergarden region through improved use of field management byadjustingirrigation amount and timing) and using soil amendment to improve water use efficiency. This will help agriculture in the Wintergarden region to cope with water shortage due the eminent competition from the rapidly growing urban water consumption near San Antonio. (g) Soil amendment Ag1000-treated plant used water 7-10% more efficiently than the control plants, and the leaves in the former had more vertical orientation than those of the latter. Thus, Ag1000 soil amendment has the potential water saving benefits. (h) Our field research indicated that corn yield can be increased up to 10% by reducing root-zone temperature through the delivery of night-time drip irrigation; this practice can be easily adopted at no cost by farmers. (i) Our field measurementin corn and sorghum varieties added to the currently accumulating evidence that challenges the long-held belief that biomass/yield formation in field crops is often accompanied with proportional water consumption. Instead, we found that a higher water use may not always lead to a higher biomass accumulation and/or grain yield, and thus there are opportunities for selecting high-yielding corn/sorghum genotypes that use less water during the growing season. (j) The results show that a 10% reduction in early irrigation water use resulted in similar or higher yields as compared to full irrigation. This demonstrated the value of regulated deficit irrigation in crop management (2895 ± 110 kg/ha and 2957 ± 93 kg/ha, respectively). (k) Our field studies from 2013 to 2015 indicated that grain yield in winter wheat was similar under different irrigation regimes (2739 kg/ha), suggesting that wheat production under limited irrigation (50% of evapotranspiration demand) seems acceptable in this region. (l) We tested three sesame varieties (S32, S28, S36) in large field plots in Uvalde, TX. Results show that number of capsules per plant was the most important seed yield component influencing seed yield. Irrigation during the bloom stage, especially late bloom stage, is critical for obtaining a high seed yield. (m) A collaboration between Texas Engineering Experiment Station (TEES) and AgriLife Research is helping torefine a computer model for optimal water management in cropping systems considering rainfall uncertainty.

Publications

  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Dong, X., Leskovar, D., Crosby, K., and Marek, T. (2014). Quantifying crop water use in arid and semi-arid regions: Opportunities based on soil-plant water relations. Journal of Arid Land Studies, 24-1: 141-144.
  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Sun, Y., Gu, L., Dickinson, R.E., Pallardy, S.G., Baker, J., Cao, Y., DaMatta, F.M., Dong, X., Ellsworth, D., Van Goethem, D., Jensen, A.M., Law, B.E., Loos, R., Martins, S.C.V., Norby, R.J., Weston, D., Winter, K. (2014). Effects of mesophyll conductance on fundamental photosynthetic parameters and their relationships estimated from leaf gas exchange measurements. Plant, Cell and Environment, 37: 978-994.
  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Dong, X., Patton, J., Gu, L., Wang, J.Z., and Patton, B. (2014). Leaf photosynthesis and plant competitive success in a mixed-grass prairie: With reference to exotic grasses invasion. Journal of Ecosystem and Ecography, 4: 152. doi: 10.4172/2157-7625.1000152.
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Dong, X., and Patton, B.D. (2015). Predicting soil water retention curves based on particle-size distribution using a Minitab macro. African Journal of Soil Science, 3(1): 079-085.
  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Zhang, Z.-S., Chen, Y.-L., Xu, B.-X., Huang, L., Tan, H.-J., and Dong, X.-J. (2014). Topographic differentiations of biological soil crusts and hydraulic properties in fixed sand dunes, Tengger Desert. J. Arid Land 7(2): 205-215.
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Zhang, Z.-S., Dong, X., Xu, B.-X., Chen, Y.-L., Zhao, Y., Gao, Y.-H., Hu, Y.-G., and Huang, L. (2015). Soil respiration sensitivities to water and temperature in a revegetated desert. JGR - Biogeosciences, 120(4): 773-787.
  • Type: Journal Articles Status: Published Year Published: 2016 Citation: Dong, X. (2016). How to put plant root uptake into a soil water flow model. F1000Research, 5:43 (doi: 10.12688/f1000research.7686.1)
  • Type: Journal Articles Status: Published Year Published: 2016 Citation: Liu, X., Dong, X., and Leskovar, D.I. (2016). Ground penetrating radar for underground sensing in agriculture: a review. International Agrophysics. 30(4):533-543.
  • Type: Journal Articles Status: Published Year Published: 2016 Citation: Dong, X., Xu, W., Zhang, Y., and Leskovar, D.I. (2016). Effect of irrigation timing on root zone soil temperature, root growth and grain yield and chemical composition in corn. Agronomy 6, 34. doi: 10.3390/agronomy6020034
  • Type: Journal Articles Status: Published Year Published: 2016 Citation: Leskovar, D.I., Othman, Y., and Dong, X. (2016). Strip tillage improves soil biological activity, fruit yield and sugar content of triploid watermelon. Soil & Tillage Res. 163: 266-273.
  • Type: Journal Articles Status: Published Year Published: 2016 Citation: Zhang, Z.-S., Zhao, Y., Dong, X.-J., Shi, Y.-F., Chen, Y.-L., and Hu, Y.-G. (2016). Evolution of soil respiration depends on biological soil crusts across a 50-year chronosequence of desert revegetation. Soil Science and Plant Nutrition 62(2): 140-149
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Liu, X., Feakins, S., Dong, X., Xue, Q., Marek, T., Leskovar, D.I., Neely, C.B., and Ibrahim, A.M.H. (2017). Experimental study of leaf wax n-alkane response in winter wheat cultivars to drought conditions. Organic Geochemistry 113: 210-223.
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Liu, X., Dong, X., Xue, Q., Leskovar, D.I., Jifon, J., Butnor, J.R., and Marek, T. (2017). Ground penetrating radar (GPR) detects fine roots of agricultural crops in the field. Plant and Soil, 423: 517-531.
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Zhang, Y.J., Hou, M., Xue, H., Liu, L., Sun, H., Li C., and Dong, X. (2017). Photochemical reflectance index and solarinduced fluorescence for assessing cotton photosynthesis under water-deficit stress. Biologia Plantarum, 62: 817-825.
  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Liu, X., Feakins, S., Dong, X., Xue, Q., Han, J., Marek, T., Leskovar, D.I., Neely, C.B., and Ibrahim, A.M.H. (2018). Evaluating leaf wax and bulk leaf carbon isotope surrogates for water use efficiency and grain yield in winter wheat. Crop Science, 59: 718-732.
  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Dong, X., Peng, B., Liu, X., Qin, K., Xue, Q., and Leskovar, D. I. (2018). An automated calculation of plant root distribution parameters based on root length density data. Applied Ecology and Environmental Research, 17: 3545-3552.
  • Type: Journal Articles Status: Submitted Year Published: 2018 Citation: Peng, B., Liu, X., Dong, X., Xue, Q., Neely, C.B., Marek, T., Ibrahim, A.M.H., Zhang, G., Leskovar, D.I., and Rudd, J. C. (2019). Root morphological traits of winter wheat under contrasting environments. Journal of Agronomy and Crop Science, in review.
  • Type: Journal Articles Status: Submitted Year Published: 2019 Citation: Liu, X., Dong, X., Ma, X., Blancaor, E.B., and Butnor, J.R. (2019). Ground penetrating radar with a high frequency antenna improves root biomass detection in sandy soil-grown winter wheat. Ground Penetrating Radar, in review.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2014 Citation: Dong, X., Leskovar, D., Pierson, B., Pierson L.S., Sharma, S.P., Gibby, A., and Pape, G. (2014). Ag1000 soil amendment increased root growth and intrinsic leaf water use efficiency in corn. The 2014 Annual Meeting of ASA-CSSA-SSSA, Long Beach, CA. November 2-5, 2014.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2014 Citation: Dong, X., Forbes, D., Speer, B., Shallock, J., Rowland, D., and Morgan, C. (2014). Effects of tillage and reduced irrigation on cotton yield in southern Texas. The 2014 Annual Meeting of ASA-CSSA-SSSA, Long Beach, CA. November 2-5, 2014.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2015 Citation: Dong, X., Xu, W., Speer, B., Zhang, Y., Christman, J., and Leskovar, D.I. Can Irrigation Timing Ameliorate High Night Temperature Stress on Corn? ASA-CSSA-SSSA Annual Meeting, Minneapolis, MN, Nov. 15-18, 2015.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2015 Citation: Dong, X., Speer, B., Zhang, Y., Hathcoat, D., Ibrahim, A.M.H., Neely, C.B., Xue, Q., Marek, T., Rudd, J.C., and Leskovar D.I. Cultivar-Irrigation Interactions in Shoot/Root Traits of 15 Wheat Varieties in Wintergarden Region. ASA-CSSA-SSSA Annual Meeting, Minneapolis, MN, Nov. 15-18, 2015.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2015 Citation: Dong, X. Root distribution and its representation for quantifying plant water uptake: An applied perspective. The 2015 Annual Meeting of ASHS New Orleans, Louisiana. August 4-7, 2015. (Invited)
  • Type: Conference Papers and Presentations Status: Published Year Published: 2015 Citation: Morgan, C.L.S. , Bell, J.M., DeLaune, P.B., Dong, X., Lewis, K.L., and Foster, J.L. Agronomic Management Strategies in Texas: Securing Soil and Improving the Efficiency of Water Use. ASA-CSSA-SSSA Annual Meeting, Minneapolis, MN, Nov. 15-18, 2015.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2015 Citation: Zhang, Y., Hou, M., Xue, H., Liu, L., Sun, H., Dong, X., and Li, C. Using photochemical reflectance index and solarinduced fluorescence to assess cotton photosynthesis under water-deficit stress. ASA-CSSA-SSSA Annual Meeting, Minneapolis, MN, Nov. 15-18, 2015.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2015 Citation: Zhang, Y., Dong, X., Speer, B., Leskovar, D. Leaf gas exchange and water use of two cotton varieties under different irrigation regimes. The 27th Annual Conference of Texas Plant Protection Association. Dec. 8-9, 2015. Bryan, TX.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2016 Citation: Murray, S.C., Knox, L., Hartley, B., Mendez, M.A., Richardson, G., Thomasson, A., Shi, Y., Rajan, N., Neely, H., Bagavathiannan, M., Dong, X., Rooney, W. (2016). High clearance phenotyping systems for season-long measurement of corn, sorghum and other row crops to complement unmanned aerial vehicle systems. Proc. SPIE 9866, Autonomous Air and Ground Sensing Systems for Agricultural Optimization and Phenotyping, 986607 (17 May 2016); doi: 10.1117/12.2228323
  • Type: Conference Papers and Presentations Status: Published Year Published: 2016 Citation: Liu, X., Dong, X., Hathcoat, D., Neely, C., Ibrahim, A.M.H., Leskovar, D.I. (2016). Testing winter wheat varieties under different irrigation regimes considering heat and disease stress in southwest Texas. Small Grains Workers Meeting, College Station, TX, August 3-4, 2016.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2016 Citation: Liu, X., Dong, X., Xue, Q., Ibrahim, A.M.H., Neely, C.B., Leskovar, D.I., and Marek, T. (2016). Path Analysis of Root/Shoot Traits and Grain Yield in Winter Wheat in Texas Wintergarden and High Plains, ASA-CSSA-SSSA Annual Meeting, Phoenix, AZ, Nov. 6-9, 2016.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2016 Citation: Murray, S.C., Richardson, G., Malambo, L., Shi,Y., Hartley, B., Demieville, J., Pekar, J., Thomasson, J. A., Popescu, S., Cope, D., Valasek, J., Olsenholler, J., Bishop, M.P., Dong, D., Rooney, W.L., Oliver, G., Ratcliff, C., Baltensperger, D., Maeda, M., Jung, J., Starek, M., Brewer, M.J., Landivar, J.A. (2016). Temporal estimates of maize plant growth in a breeding program using ground based and unmanned aerial vehicle systems,ASA-CSSA-SSSA Annual Meeting, Phoenix, AZ, Nov. 6-9, 2016.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2017 Citation: Raman, R., Dong, X., Murray, S., Rooney, B., Malla, S. (2017). Characterization of drought tolerance traits in corn and sorghum: a phenotypical approach, ASA-CSSA-SSSA Annual Meeting, Tampa, FL, Oct. 21-25, 2017.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2017 Citation: Liu, X., Dong, X., Xue, Q., Leskovar, D.I., Jifon, J., Butnor, J.R., and Marek, T. (2017). Using Ground Penetrating Radar to Detect Fine Roots of Agricultural Crops in the Field, ASA-CSSA-SSSA Annual Meeting, Tampa, FL, Oct. 21-25, 2017.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2017 Citation: Raman, R., Dong, X., Murray, S., Rooney, B., and Malla, S. (2017). Water-Use Efficiency of Selected Corn and Sorghum Genotypes in Southwest Texas, The 29th Annual Conference of Texas Plant Protection Association. Dec. 5-6, 2017. Bryan, TX.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2017 Citation: Dong, X., Sieckenius, S., Djidonou, D., Leskovar, D.I., Joshi, V.. Soil Water Infiltration and Retention Under Saline and Sodic Conditions. Oral presentation to the 2017 Annual Meeting of ASA-CSSA-SSSA, Tampa, FL. October 21-25, 2017.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Dong, X. and Morgan, G. (2018). Leaf osmotic potentials of selected cotton varieties under different irrigation regimes in southwest Texas. The Beltwide National Cotton Conference, January 3-5, 2018. San Antonio, TX.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Raman, R., Dong, X., Murray, S. C., Rooney, W. L., and Malla, S. (2018). Identification of yield potential of different corn and sorghum genotypes in southwest Texas. Southern Branch of American Society of Agronomy Annual Meeting. February 4-6, 2018, Jacksonville, FL.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Qin K., Leskovar D.I., Dong X., Jifon J. (2018). Effects of humic substances and growth environments on the rhizosphere microbial biomass in a bell pepper system. HortScience 53 (9), S100-S101
  • Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: Dong, X., Sieckenius, S., Peng, B., Morgan, G., and Joshi, V. (2019). Cotton yield and fiber quality in relation to leaf and canopy traits under different irrigation regimes in southwest Texas. The Annual Beltwide National Cotton Conference, January 8-10, 2019. New Orleans, LA.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: Dong, X., Sieckenius, S., Peng, B., Xue, Q., Ibrahim, A.M.H. (2019). Predicting leaf rust infection rate in winter wheat using normalized difference vegetation index. ASA-Southern Regional Conference, Birmingham, AL., February 3-5, 2019.


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

Outputs
Target Audience:During this reporting period, Xuejun Dong and his group members delivered four presentations to crop/soil researchers, graduate students and/or the general public in regional and national conferences. On February 5, 2018, Rahul Raman gave a talk in the Southern Branch Annual Meeting of American Society of Agronomy, in Jacksonville, FL. The topic was on yield performance of novel genotypes of corn and sorghum in southwest Texas. On March 29, 2018, Dong delivered a lecture entitled ' Root water uptake: integrating measurements and modeling approaches ' to a group of graduate students at Texas A&M University, College of Agriculture and Life Sciences. On August 2, 2018, Bin Peng gave a presentation entitled 'Effects of environment x variety on root traits of winter wheat' at the Small Grain Worker's Workshop, held in College Station, TX. Dong hosted the Annual Soils Critic meeting, a regular gathering of soil/crop scientists at Texas T&M and beyond, at Uvalde during August 25-26, 2018. He also gave a presentation entitled 'Soil-plant water relations and crop production in southwest Texas.' Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?During this reporting period, X. Dong's program provided training and professional development for one graduate student (Rahul Raman), one research assistant (Shane Sieckenius) and one visiting scholar (Bin Peng). Raman analyzed the data of corn/sorghum drought tolerance traits that he had collected in past two years, wrote his M.S. thesis and successfully defended it on July 6, 2018. Sieckenius continued developing his skills in using the ground penetrating radar for soil and root survey under field conditions. Peng has participated in various research projects and has completed writing a journal paper on the effects of genotype and environments on root traits of winter wheat, which has been submitted to Journal of Agronomy and Crop Science. How have the results been disseminated to communities of interest?The research results were summarized as oral/poster presentations in professional conferences, online stories, as well as peer-reviewed journal publications. We disseminated the recent research findings to colleagues in the southern USA (through ASA-Southern Branch annual meeting), and soil and crop researchers in Texas (at the Soils Critic meeting and Small grain Workers' meeting). Dong also worked with Uvalde Leader News reporter Kimberly Rubio on developing a story featuring the impact of excessive rainfall on cotton yield and quality in southwest Texas. Dong demonstrated to local farmers and extension agents during the Vegetable Spring Field Day held at Uvalde, TX on May 11, 2018 on using the mustard cover crops to improve soil health in southwest Texas. Finally, our continued research on GPR application, leaf wax as proxy of indicating plant water use efficiency, as well as comparative root traits in the U.S. southern Great Plains regions, were published or under review by peer-reviewed journals. What do you plan to do during the next reporting period to accomplish the goals?Next period will be focused on new progress made from October 1, 2018 to January 29, 2019, and as well as summarizing the research achievements made during the past five years.

Impacts
What was accomplished under these goals? Goal 1: Research on crop shoot/root traits under field conditions were conducted in winter wheat, corn, sorghum, and cotton. In this reporting period, we conducted the 2nd year survey of the winter wheat nursery plots in Castroville, TX using a push-wheel phenotyping cart equipped with multiple sensors. We scanned 500 plots for five times from March 12 to May 1, 2018. Data analysis is in progress to use linear regression to relate leaf rust infection rate to easily measured vegetation indices obtained from an ACS-430 Crop Circle sensor mounted on the sensing cart. We combined leaf wax carbon/hydrogen isotope composition data measured in 2015 and 2016 to provide further results reinforcing the findings obtained earlier in our paper published in Organic Geochemistry. This year's new results have been published in Crop Science, which provides a further support for the notion that leaf alkane carbon and hydrogen isotope compositions in wheat are better indicators of leaf water use efficiency than the bulk leaf carbon isotopes that have been widely used in past decades. Our most recent work in GPR-based crop root phenotyping indicates that, using a 2.6 GHz antenna, as compared with a 1.6 GHz antenna, significantly improved accuracy of predicting root biomass of winter wheat under field conditions. The work has been submitted to Ground Penetrating Radar (the first journal dedicated to GPR research) for review. By analyzing the corn and sorghum phenotyping data collected in southwest Texas (graduate student Rahul Raman's work), some interesting trends were observed to contrast the field growth performance and water use patterns of 15 corn and 15 sorghum genotypes growing side-by-side in the same field in 2016 and 2017. (i) By calculating seasonal water use of different corn/sorghum genotypes, we found that a higher water use may not always lead to higher biomass accumulation and/or grain yield formation, and thus there are opportunities for selecting high-yielding corn/sorghum genotypes that use less water during the growing season. (ii) A negative relationship between number of green leaves and grain yield was found in corn genotypes, whereas, in sorghum genotypes, the relationship was positive. (iii) Overall, leaf thickness, leaf dry matter content, osmotic potential, plant height, and NDVI are the most important predictors of grain yield of corn and sorghum genotypes. By analyzing the root morphological traits data collected in 2015-2017 for selected 10 winter wheat varieties in contrasting environments in Texas Wintergarden and High Plains regions, we have obtained the following results: (i) Root length density (RLD) decreased, while specific root length (SRL) and specific root surface area (SSA) increased with soil depth. (ii) Compared with Uvalde (a warmer, wetter and clay soil-dominated site), the environment in Bushland (a cooler, drier and loamy soil-dominated site) promoted deeper root growth, but increased root tissue density, reduced specific root length and root specific surface area, suggesting that the dichotomy of 'conservative' vs. 'acquisitive' root strategy of the root economic spectrum framework partially applied in describing the variations of wheat root traits measured in contrasting environments. (iii) Both SRL and RLD were positively associated with grain yield, with the former relation stronger under drought stress. There is an opportunity of using easily measurable vegetation indices to predict leaf water potentials for field crops. Once this relationship be established and verified under field conditions, it is possible to more readily describe drought response of large number of crop genotypes under field conditions based on remotely sensed vegetation indices. We used a push-wheel sensing cart, as well as a back-pack sensing frame to measure diurnal changes in NDVI for corn, cotton and wheat in relation to leaf water potential in the 2018 growing season and the analysis of the data is in progress Goals 2/3: We developed computer programs (R and Minitab) for automated data processing to extract root distribution parameters of field crops using measured root length density data. In particular, the data processing method can help to estimate normalized root length density, which is useful for quantifying plant root water uptake under field conditions. This work has been accepted for publication in Appl. Ecol. Environ. Res., and the computer code is available through Zenodo at: https://zenodo.org/record/1484655#.XCPKy2l7lhF

Publications

  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Zhang, Y.J., Hou, M., Xue, H., Liu, L., Sun, H., Li C., and Dong, X. (2018). Photochemical reflectance index and solar-induced fluorescence for assessing cotton photosynthesis under water-deficit stress. Biol. Plant. 62: 817-825. DOI: 10.1007/s10535-018-0821-4
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Liu, X., Feakins, S., Dong, X., Xue, Q., Han, J., Marek, T., Leskovar, D.I., Neely, C.B., and Ibrahim, A.M.H. (2018). Evaluating leaf wax and bulk leaf carbon isotope surrogates for water use efficiency and grain yield in winter wheat. Crop Sci. doi: 10.2135/cropsci2018.07.0452.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Dong, X. and Morgan, G. (2018). Leaf osmotic potentials of selected cotton varieties under different irrigation regimes in southwest Texas. The Beltwide National Cotton Conference, January 3-5, 2018. San Antonio, TX.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Raman, R., Dong, X., Murray, S. C., Rooney, W. L., and Malla, S. (2018). Identification of yield potential of different corn and sorghum genotypes in southwest Texas. Southern Branch of American Society of Agronomy Annual Meeting. February 4-6, 2018, Jacksonville, FL.
  • Type: Journal Articles Status: Accepted Year Published: 2018 Citation: Dong, X., Peng, B., Liu, X., Qin, K., Xue, Q., and Leskovar, D. I. (2018). An automated calculation of plant root distribution parameters based on root length density data. Appl. Ecol. Environ. Res., accepted as of November 22, 2018.


Progress 10/01/16 to 09/30/17

Outputs
Target Audience:During this reporting period, Xuejun Dong's group delivered several taks to both crop researchers and general public in local and national/international conferecnes. On May 18, 2017, Xuejun Dong gave a talk on the Joint Vegetable and Wheat Field Day held at the Uvalde Research and Extension Center and discussed about the sucess of detecting rust disease in wheat using multispectal phenotyoing under field conditions. On June 21, 2017, Dong delivered a seminar entitled 'Soil-plant water relations and agricutlural crop proeduction in arid regions' to a grpupd visitors from Uzbekistan and Turkmanistan as part of the Cochran Felowship program. During the joint annual meeting of American Society of Agronomy, Crop Science Society of America and Soil Science Society of America, held in Tampa, Florida, October 21-25, 2017, Xuejun Dong, Xiuwei Liu (Post Doc researcher) and Rahul Raman (MS student) each gave a presentation deseminating the recent research findings from the Uvalde agronomy group with topics related to (a) soil water infiltration and retention under saline and sodic conditions, (b) the use of ground penetrating radar in detecting crop fine roots under field conditions, and (c) the genotype by environment interactions of corn and sorghum leaf traits under drought conditions in southwest Texas. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?This project provided training and professional development for one Post Doc researcher, one MS student and one undergraduate student worker. In September 2017, Dr. Xiuwei Liu travelled to University of Southern California (USC) to measure stable isotope compositions of plant leaf wax. During the 40 days at USC, Xiuwei worked under the supervision of Professor Sarah Feakins. Sponsored by Dr. Xuejun Dong's program, Rahul Raman (MS graduate student) finished his 2nd year field work measuring corn/sorghum drought tolerance traits under field conditions. Rahul is co-advised by professors Seth Murray, Bill Rooney and Subas Malla. During this reporting period, Dalton Thompson (undergraduate student at Southwest Texas Junior College in Uvalde, TX) received continued training to conduct various field measurements and sampling to support plant stress physiology research at Uvalde. How have the results been disseminated to communities of interest?The research results were summarized as oral/poster presentations in professional conferences, online stories, as well as peer-reviewed journal publications. Dr. Xiuwei Liu presented a poster to the ASA-CSA-SSSA annual meeting held in Tampa, Florida, highlighting the successful application of ground penetrating radar to quantify crop fine roots. The work later was published in Plant and Soil. In may 2017, Dr. Xuejun Dong introduced his recent work on ground-based multi-spectral phenotyping to the combined vegetable and wheat field day held at the Uvalde research Center, which was attended by crop researchers and local producers. Xuejun Dong also worked with ag reporter Paul Schattenberg to release the key research results on leaf wax and root phenotyping through online stories published in AgriLife Today. What do you plan to do during the next reporting period to accomplish the goals?We will continue our work using the ground-based phenotyping tools (GPR and a push-wheel sensing cart and back-pack sensing frame) to measure crop traits under field conditions. We will further analyze the data collected using field phenotyping tools to generate peer-reviewed publications. Finally, we will further develop and test the dynamic programming model for irrigation management in crop production.

Impacts
What was accomplished under these goals? Goal 1. Research on crop traits under field conditions were conducted in winter wheat, corn, sorghum and energy cane. (a) In collaboration with the UAS team at Texas A&M Corpus Christi and breeding teams at College Station and Amarillo, we used a ground-based phenotyping cart to test if the presence of leaf rust in winter wheat is reflected in measured vegetation indices. The work was done in April, 2017 at the Castroville Wheat Nursery, Castroville, Texas. The results showed that canopy reflectance at red-edge band can to some extent reflect the presence of leaf rust in winter wheat; however, the relationship is weaker after flowering with increased leaf aging. (b) A collaboration between Texas A&M crop researchers and an ecologist at University of Southern California yielded new results highlighting the potential of using compound-specific alkane isotopes as precision predictors of water use efficiency (WUE) and grain yield in winter wheat, which would help to expedite the process of crop breeding for improved WUE in wheat as well as other agricultural crops. Here the keyword 'precision' refers to the use of simpler molecules (such as alkane carbon/hydrogen isotopes), as opposed to the complex ones represented by the bulk leaf carbon isotope fractionation, as a basis for marker-assisted selection in identifying water efficient crop cultivars in a breeding program. This work was conducted using the same 10 winter wheat varieties planted for two consecutive years in two Texas locations - Uvalde (located in Texas Wintergarden) and Amarillo (located in Texas High Plains) - with different soil and climate conditions. (c) In collaboration with a plant physiologist at USDA Forest Service, as well as utilizing the multi-location trials within Texas A&M AgriLife Research, we developed a method to measure crop fine roots using ground penetrating radar (GPR) system. Specifically, the field test was done in winter wheat (growing in Uvalde, Amarillo and Dilley, Texas) and energy cane (growing in Weslaco, Texas). Using a 1600 MHz antenna, we tested 4 different GPR signal indices, and found that the average GPR pixel intensity index without intensity threshold was the best in predicting fine root biomass and diameter of winter wheat and sugar cane. GPR has beeen successfully used to quantify tree coarse (thick) roots in forest ecosystems in past two decades. But we believe our work in 2017 (published in Plant and Soil) possibly is the first report demonstrating that GPR can measure fine root characteristics at a bulk soil level. Our results support the use of GPR technology as a vital component of crop root phenotyping studies in the future. Goals 2 and 3. A collaboration between Texas Engineering Experiment Station (TEES) and AgriLife Research is helping to refine a computer model for optimal water management in cropping systems considering rainfall uncertainty. We consider the objective of maximizing the crop production when the optimizing factor is minimizing the use of water (irrigation). Furthermore, finding an optimal irrigation schedule involves many different factors such as the geographic location, the type of soil, the date in a year, and the type of crops, to name just a few. We designed a stochastic dynamic programming model to find an optimal irrigation schedule, where those factors are represented as parameters of the optimizing functions incorporating the probability of precipitation as a factor of uncertainty. We consider a discrete time system with n stages, where n could represent seven days in a weekly cycle, or the number of weeks involved in a crop production cycle. Each stage is denoted as t, with t = 1, ..., n. To decide the amount of irrigation at time t, one needs to know the (potential) amount of water contained in the soil at time t, denoted as w_t, and the (potential) amount of water needed by the crop to attain its optimal growth at time t, denoted as d_t. These two variables serve the state variables. Each variable has the (normalized) value range of between zero and one. The value of w_t being zero means that the soil is completely dry, and the value of one means that the soil is completely saturated at the time t. The value of d_t being zero means that there is no need of water for the crop to achieve its optimal growth, and the value of one means that there definitively needs be irrigated at the time t. The main idea is that at stage t, given an initial state s_t = (w, d) and the probability of precipitation during t, we want to compute the expected optimal (maximizing) gain with the expected optimal (minimizing) cost, and decide on the action to take, which will have impact on the optimal cost and gain in the next stage. Thus, a stage is defined by the following four components: (i) An initial state s_t in S_t, where S_t is the set of feasible initial states, in which each state is represented as a pair (w, d), where 0 <= w <= 1 denotes the amount of water contained in the soil, and 0 <= d <= 1 the amount of water demand by the crop to attain its optimal growth at the time. (ii) A decision variable at a_t in A_t, where A_t is the set of feasible actions (whether to irrigate or not). (iii) A local cost/gain function c_t (s_t, a_t) that represents the cost of water usage with the gain of optimal crop growth if, upon the initial state s_t, the action a_t is taken. (iv) A state transition function f_t (s_t, a_t) that transitions the system to the next state s_{t+1}. The core of the dynamic programming model is to achieve the expected optimal gain G_t (s_t) by maximizing optimal policy over stages t, t + 1, ..., n.

Publications

  • Type: Conference Papers and Presentations Status: Published Year Published: 2017 Citation: Dong, X., Sieckenius, S., Djidonou, D., Leskovar, D.I., Joshi, V.. Soil Water Infiltration and Retention Under Saline and Sodic Conditions. Oral presentation to the 2017 Annual Meeting of ASA-CSSA-SSSA, Tampa, FL. October 21-25, 2017.
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Liu, X., Feakins, S., Dong, X., Xue, Q., Marek, T., Leskovar, D.I., Neely, C.B., and Ibrahim, A.M.H. (2017). Experimental study of leaf wax n-alkane response in winter wheat cultivars to drought conditions. Organic Geochemistry 113: 210-223. http://dx.doi.org/10.1016/j.orggeochem.2017.07.020
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Liu, X., Dong, X., Xue, Q., Leskovar, D.I., Jifon, J., Butnor, J.R., and Marek, T. (2017). Ground penetrating radar (GPR) detects fine roots of agricultural crops in the field. Plant and Soil doi:10.1007/s11104-017-3531-3.
  • Type: Journal Articles Status: Under Review Year Published: 2017 Citation: Zhang, Y.J., Hou, M., Xue, H., Liu, L., Sun, H., Li C., and Dong, X. (2017). Photochemical reflectance index and solar-induced fluorescence for assessing cotton photosynthesis under water-deficit stress. Biologia Plantarum (revised version submitted September 10, 2017).
  • Type: Conference Papers and Presentations Status: Published Year Published: 2017 Citation: Leskovar, D.I., Othman, Y., and Dong, X. (2017). Strip Tillage Improves Soil Biological Activity, Fruit Yield and Sugar Content of Triploid Watermelon. Watermelon Research and Development Group (WRDG) Meeting. Feb. 3-4, 2017. Mobile, Alabama.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2017 Citation: Raman, R., Dong, X., Murray, S., Rooney, B., Malla, S. (2017). Characterization of drought tolerance traits in corn and sorghum: a phenotypical approach, ASA-CSSA-SSSA Annual Meeting, Tampa, FL, Oct. 21-25, 2017.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2017 Citation: Liu, X., Dong, X., Xue, Q., Leskovar, D.I., Jifon, J., Butnor, J.R., and Marek, T. (2017). Using Ground Penetrating Radar to Detect Fine Roots of Agricultural Crops in the Field, ASA-CSSA-SSSA Annual Meeting, Tampa, FL, Oct. 21-25, 2017.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2017 Citation: Raman, R., Dong, X., Murray, S., Rooney, B., and Malla, S. (2017). Water-Use Efficiency of Selected Corn and Sorghum Genotypes in Southwest Texas, The 29th Annual Conference of Texas Plant Protection Association. Dec. 5-6, 2017. Bryan, TX.


Progress 10/01/15 to 09/30/16

Outputs
Target Audience:During this reporting period, Xuejun Dong worked with six growers in southwst Texas to gain their supprot in a soil conservation (through the use of limited tillage and cover corps) proposal. One of the growers agreed to donate 10 acre land for use in field testing of soil health involving cover crops. In March 2016, Xuejun delvierd a lecture on modeling of plant root water uptake for crop breeding to a groupd of gradute students at Texas A&M University, College Station. In August 2016, Xiuwei Liu (Post Doc researcher) delivered a talk about winter wheat responses to irrigation regimes in the Texas Small Grains Workers annual meeting at College Station. In Novermber 2016, Xiuwei and Xuejun attended the American Society fo Agronomy Annual Meeting in Phoenix, AZ and gave a presentation on shoot/root traits of winter wheat sampled at two locaitons in Texas with contrasting climate and soil types. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?This proejct provided training and professional development for one Post Doc researcher, one MS student and one undergraduate student worker. In June 2016, Dr. Xiuwei Liu attended a training workshop for using the ground penetrating radar (GPR) at the Geophysical Survey Systems, Inc. in Nashua, NH. In September 2016, Dr. Liu went to University of Southern California to get trained in using the stable isotope technique to measure plant leaf wax and carbon/hydrogen isotope composition. Sponsored by Dr. Xuejun Dong's prgoram, Rahul Raman (MS graduate student) started this first summer field work June 1, 2016. Rahul conducted field surveys on corn and sorghum physiological traits related to water use efficiency under different irrigation regimes. During this reporting period, Dalton Thompson (undergraduate student at Southern Texas Junior College in Uvalde, TX) was trainted to do various field measurment and sampling to support plant stress physiology research at Uvalde. How have the results been disseminated to communities of interest?The research results were summarized as an oral presentation given to the annual Small Grains Workers' meeting, held at Texas A&M University, College Station, August 3-4, 2016. The title of the presentation was "Testing winter wheat varieties under different irrigation regimes considering heat and disease stress in southwest Texas". A poster presentations entitled "Path analysis of root/shoot traits and grain yield in winter wheat in Texas Wintergarden and High Plains" was given to the joint annual meeting of American Society of Agronomy, Crop Science Society of America and Soil Science Society of America to be held in Phoenix, AZ, November 6-9, 2016. Also, March 22, 2016, X. Dong was invited to give a graduate lecture at College Station, TX to discuss about current development in modeling methods for quantifying plant root water uptake as part of research efforts in breeding-based plant improvement. What do you plan to do during the next reporting period to accomplish the goals?In the next reporting cycle, ground-based phenotyping tools (GPR and a push-wheel or back-pack sensing frame) will be used in field phenotyping of row crops and/or vegetable crops. Also discussed will be the results using the newly developed dynamic programming computer model for irrigation management in crop production.

Impacts
What was accomplished under these goals? Goal 1. Research on crop traits under field conditions were conducted in winter wheat, corn, sorghum and sesame. (a) We tested ten winter wheat varieties, namely 'Duster', 'Fannin', 'Fuller', 'Gallagher', 'TAM 112', 'TAM 114', 'TAM 304', 'TAM 305', 'TAM 401', and 'WB Cedar', for shoot/root traits under different irrigation regimes in two locations of Texas: Uvalde (Wintergarden) and Amarillo (High Plains). In both locations, the tests were conducted under two irrigation regimes, namely, full irrigation (100% of crop evapotranspiration (ET) replenishment) and deficit irrigation (60% of ET replenishment). Three traits were considered: specific leaf area (SLA, defined as leaf area per unit leaf mass), specific root length (SRL, root length per unit of root mass) and root to shoot ratio (RS). The direct and indirect effects of the three variables to grain yield was conceptualized in a path analysis model and statistical resampling method was used to test for significance of the various path coefficients. Results indicated that in Uvalde (clay soil) about 75% of roots were found at shallow soil depth (0-40 cm), while in Amarillo (silty clay loam) the roots were about evenly distributed between shallow (0-40 cm) and deeper (40-100 cm) profile. Path analysis suggested that in Amarillo SLA had a stronger influence on grain yield, while in Uvalde the greater influence to grain yield came from SRL instead. This result will motivate future investigation to pinpoint the underlying reasons for the contrast in root distribution patterns as well as their significne for wheat breeding. (b) We also characterized leaf wax alkane concentration and compound-specific carbon/hydrogen isotopes in the tested winter wheat varieties obtained from two Texas locations. This work was the result of a close collaboration between Texas A&M and University of Southern California researchers. Leaf cuticular wax forms the boundary between plant leaf cells and the atmosphere, and reflects physiological and biochemical responses of plants to environment. We found leaf wax composition patterns with longer n-alkane chain length at Uvalde were associated with higher temperatures, and not with aridity in this study. Leaf wax alkane concentration and leaf wax isotopes as well as bulk leaf δ13C value all increased at the higher and drier site (Amarillo) and under deficit irrigation and correlated particularly with bulk δ13C. This is the first time that leaf wax alkane concentrations have been shown to vary systematically with environmental conditions in monocots and has implication for understanding plant functional biology and reconstructing past grassland ecosystems. Significantly negative relationships of bulk δ13C, δD_wax (hydrogen isotope concentration) and δ13C_wax with grain yield and WUE (water use efficiency) were found under full irrigation in Uvalde and bulk δ13C and δD_wax under deficit irrigation in Amarillo. The results show the potential for compound-specific approaches to pinpoint physiological and biochemical differences between wheat varieties. (c) To cope up with limited water conditions, it is needed to identify crop genotypes that can withstand drought, thereby maintaining better growth, development, and yield. We tested 15 genotypes of corn (Zea mays L.) and sorghum (Sorghum bicolor L.) in Uvalde under well watered and water deficit conditions. The effect of irrigation was not significant due to abundant rains received in May-June 2016. So our focus for this season is in genotype performance. The 15 genotypes of corn had tropical or temperate origin, while the 15 genotypes of sorghum consisted of inbreds and hybrids. In corn, tropical or partially temperate - tropical derived genotypes yielded higher than mostly temperate derived ones. In sorghum, hybrids yielded better than inbred but showed lower leaf area index as compared to inbreds. Hybrid genotypes that were considered as drought tolerant based on their performance at different locations earlier yielded better and showed significantly different result (p-value 0.0001) as compared to hybrid genotypes susceptible to drought and inbred genotypes that were considered as drought susceptible and drought tolerant. In both corn and sorghum, genotypes having higher leaf area index (LAI) showed lower yield. Further test under different irrigation regimes is needed to identify the underlying reason and agronomic significance. (d) Finally, we characterized sesame growth and yield responses to irrigation management in southwest Texas. Sesame has high capacity of drought tolerance and fits well into the cropping systems in Texas. Under shortage of water for agricultural crop production, growers in Texas are increasingly interested in using sesame in their crop rotation systems. However, information is lacking on performance of different varieties under different irrigation regimes. We tested three varieties provided by Sesame Co. under full and deficit irrigation regimes in Uvalde. In 2015, each of the three sesame varieties (S28, S32 and S36) was grown in large field plots (each of 0.7 acre) and replicated three times in a 12-acre field irrigated with center pivot system. Results show that, in terms of seed yield, variety S32 performed best among the three varieties tested. S36 appeared to be more suitable for limited irrigation condition, instead of high water input production. Overall, our data suggested that number of capsules per plant was the most important seed yield component influencing seed yield. Irrigation during the bloom stage, especially late bloom stage, could be critical for a high seed yield. Goals 2 and 3. To support optimal water management in cropping systems, a computer model has been developed in order to simulate crop growth and water balance. This crop growth/water use model is linked with a stochastic dynamic programming model for optimal irrigation management during the growing season, utilizing both the information of realized (past) rainfall, and the unknown (stochastic) future rainfall. This work is a result from a collaboration between researchers at Texas A&M AgriLife and Texas Engineering Experiment Station (TEES). Currently, the model is being parameterized using the measured data of biomass growth, soil water, and daily weather (maximum/ minimum temperatures and precipitation) of the winter wheat crop growing in two Texas locations, Uvalde and Amarillo, with contrasting soil and climate.

Publications

  • Type: Journal Articles Status: Published Year Published: 2016 Citation: Liu, X., Dong, X., and Leskovar, D.I. (2016). Ground penetrating radar for underground sensing in agriculture: a review. International Agrophysics. 30(4):533-543. doi: 10.1515/intag-2016-00010
  • Type: Journal Articles Status: Published Year Published: 2016 Citation: Dong, X., Xu, W., Zhang, Y., and Leskovar, D.I. (2016). Effect of irrigation timing on root zone soil temperature, root growth and grain yield and chemical composition in corn. Agronomy 6, 34. doi: 10.3390/agronomy6020034
  • Type: Journal Articles Status: Published Year Published: 2016 Citation: Leskovar, D.I., Othman, Y., and Dong, X. (2016). Strip tillage improves soil biological activity, fruit yield and sugar content of triploid watermelon. Soil & Tillage Res. 163: 266-273.
  • Type: Journal Articles Status: Published Year Published: 2016 Citation: Zhang, Z.-S., Zhao, Y., Dong, X.-J., Shi, Y.-F., Chen, Y.-L., Hu, Y.-G. (2016). Evolution of soil respiration depends on biological soil crusts across a 50-year chronosequence of desert revegetation. Soil Science and Plant Nutrition 62(2): 140-149
  • Type: Conference Papers and Presentations Status: Published Year Published: 2016 Citation: Murray, S.C., Knox, L., Hartley, B., Mendez, M.A., Richardson, G., Thomasson, A., Shi, Y., Rajan, N., Neely, H., Bagavathiannan, M., Dong, X., Rooney, W. (2016). High clearance phenotyping systems for season-long measurement of corn, sorghum and other row crops to complement unmanned aerial vehicle systems. Proc. SPIE 9866, Autonomous Air and Ground Sensing Systems for Agricultural Optimization and Phenotyping, 986607 (17 May 2016); doi: 10.1117/12.2228323
  • Type: Conference Papers and Presentations Status: Published Year Published: 2016 Citation: Liu, X., Dong, X., Hathcoat, D., Neely, C., Ibrahim, A.M.H., Leskovar, D.I. (2016). Testing winter wheat varieties under different irrigation regimes considering heat and disease stress in southwest Texas. Small Grains Workers Meeting, College Station, TX, August 3-4, 2016.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2016 Citation: Liu, X., Dong, X., Xue, Q., Ibrahim, A.M.H., Neely, C.B., Leskovar, D.I., and Marek, T. (2016). Path Analysis of Root/Shoot Traits and Grain Yield in Winter Wheat in Texas Wintergarden and High Plains, ASA-CSSA-SSSA Annual Meeting, Phoenix, AZ, Nov. 6-9, 2016.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2016 Citation: Murray, S.C., Richardson, G., Malambo, L., Shi,Y., Hartley, B., Demieville, J., Pekar, J., Thomasson, J. A., Popescu, S., Cope, D., Valasek, J., Olsenholler, J., Bishop, M.P., Dong, D., Rooney, W.L., Oliver, G., Ratcliff, C., Baltensperger, D., Maeda, M., Jung, J., Starek, M., Brewer, M.J., Landivar, J.A. (2016). Temporal estimates of maize plant growth in a breeding program using ground based and unmanned aerial vehicle systems,ASA-CSSA-SSSA Annual Meeting, Phoenix, AZ, Nov. 6-9, 2016.


Progress 10/01/14 to 09/30/15

Outputs
Target Audience:During this reporting period, X. Dong interacted with colleagues both in the Texas A&M University System, the professional societies and the Wintergarden produicers/residents to deliver science-based information. He supervised two student workers to conduct agronomy field research. He was invited to deliver a talk entitled "Root distribution and its representation for quantifying plant water uptake: An applied perspective" to the American Society of Horticultural Sciences annual meeting, which was held in New Orleans, Louisiana, August 4-7, 2015. He discussed with local producers and wheat researchers about root traits, water use and yield of winter wheat varieties in the Wintergarden region during the Wheat-Vegetable Joint Field Day at the Uvalde Research Center in April 2015. He also helped to reslove a lawn health problem reported by a local resident. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?One full-time research technician and two student workers were trained to carry out various field and lab experiments. This project, as well as additional funds we sought from various sources, allowed us to hire one post-doc research associate and one master student. The project also attracted two visiting scholars, one from Agricultural University of Hebei, China, and the other from China Agricultural University. These two scholars brought in new ideas to our programs. How have the results been disseminated to communities of interest?The research results were summarized as poster presentations (5 abstracts) to the joint annual meeting of American Society of Agronomy, Crop Science Society of America and Soil Science Society of America to be held in Mineapolis, MN, November 15-18, 2015. One oral presentation on cotton water use was delivered at the Beltwide Cotton Conference held in San Antonio, January 5-7, 2015. Also, X. Dong was invited to give a presentation on root physiology during the Annual Meeting of American Society of Horticultural Scinces, in New Orleans, Louisiana, August 4-7, 2015. To communicate our research findings to local growers and professionals, X. Dong delivered a presentation to the Joint Wheat-Vegetable Crops Field Day, which was held at the Texas A&M AgriLife Rsearch - Uvalde, April 21, 2015. Finally, X. Dong distributed his computer programs on plant root water uptake and modeling to Zenodo, a rapidly developing research data repository created by OpenAIRE and CERN. This will provide uniquely citable software products for use and collaboration within an international community of researchers. What do you plan to do during the next reporting period to accomplish the goals?The next reporting cycle will feature the use of remote sensing tools for plant trait phenotyping. Also research on sesame will be highlighted.

Impacts
What was accomplished under these goals? Goal 1. Research on crop traits under field conditions were conducted in corn, winter wheat and cotton. (a) We tested the effect of irrigation timing on corn growth and yield. The hypothesis was that high night temperature stress may compromise corn growth and yield; delivering irrigation water through drip in the early evening may help to reduce the root zone temperature and thus improve plant growth under high-temperature stress situations. Our data show that corn plants grown under night-time drip irrigation tended to have more root growth and higher yields. On the other hand, ear height, the kernel chemical composition, leaf chlorophyll content and stomatal conductance did not exhibit a clear response to irrigation timing. The cooling effect of night-time drip irrigation is related to the average daily soil temperature, with larger extent of temperature reduction occurring on days when soil tended warmer than when it was cooler. Additional field measurements and controlled experiments are needed in order to prove the causal relationship between irrigation timing and corn growth and yields. (b) We tested 15 winter wheat varieties to investigate how photosynthetic and root water use traits are linked to grain yield under different irrigation regimes (100%, 75% and 50% of evapotranspiration demand). The traits we considered include specific leaf area, leaf area index, root length density and root distribution pattern. In both the 2013-2014 and 2014-2015 seasons, grain yield was similar under different irrigation regimes (2739 kg/ha). Thus production under limited irrigation (50% of evapotranspiration demand) is preferred. Leaf rust infection caused 26%, 11% and 13% of yield reduction under 100%, 75% and 50% irrigation regime, respectively. Two varieties most susceptible to leaf rust ('TAM 112' and 'Coronado') also had the lowest grain yields. Roots tended to grow deeper at intermediate level of irrigation (75% ET demand) than at lower (50%) or higher (100%) irrigation. (c) In 2015, we focused on characterizing water use traits of two widely planted varieties in the U.S. cotton belt, 'DP1044' and 'PHY499'. Understanding how they cope with extreme water stress through regulation of leaf gas exchange and water status can help us make a better farm decision in irrigation management. Knowledge of the field performance of these model varieties also provides hints for future breeding efforts aiming at improved water use efficiency. An interesing aspect of our experiment is that it compared the two cotton varieties side-by-side in the same field in southwest Texas under contrasting irrigation regimes. Results show that under limited water supply both DP1044 and PHY499 exhibited drought adaptation water use strategy, although stomatal conductance of DP1044 was more responsive to severe drought, which was accompanied by increased leaf water use efficiency. On the other hand, PHY499 responded to the increased water availability by increasing leaf an root growth, as well as stand water consumption. Goal 2. The main work done to address this objective includes further soil physical characteization and computer programming to assist transpiration modeling. (a) Soil hydraulic property characterization. We used Rosetta software to estimate parameters of soil water retention curves based on soil texture and bulk density data. Alternatively, soil water retention curves were fitted based on data of soil water potential and soil water content directly measured at the same depth of soil under field conditions. (b) A software was developed to quantify canopy scale transpiration and light use efficiency for field crops. The method was originally proposed by John Norman et al. and published on the website of Li-Cor Bioscience in 2002. Despite the important implications the paper has for crop transpiration study, it has not received its due attention, mainly because of the lack of an updated software support. We had decided to do this job under current project and the main computer code has been completed. (c) Some data management work was done to adapt a specific root uptake model for general purpose use. The main paper was published in F1000Research and the software distributed at https://zenodo.org. Goal 3. This year's effort was mainly concentrated on characterizing the baseline data needed to calibrate and evaluate the DSSAT cropping system model in the Wintergarden region. The data collected and organized fall into three types: (a) Long-term weather data in past 15 years from 2001-2015, including maximum and minimum air temperatures, solar radiation and precipitation on a daily basis. (b) Soil properties under different tillage regimes. This inlcudes soil texture, bulk density, saturated hydraulic conductivity and total C to total N ratio. (c) Plant growth and biomass partition data under different irrigation regimes. This includes above-ground biomass data from harvests at 2-weeks intervals during growing seasons for wheat, corn and cotton.

Publications

  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Zhang, Z.-S., Dong, X., Xu, B.-X., Chen, Y.-L., Zhao, Y., Gao, Y.-H., Hu, Y.-G., and Huang, L. 2015. Soil respiration sensitivities to water and temperature in a revegetated desert. JGR - Biogeosciences DOI: 10.1002/2014JG002805
  • Type: Journal Articles Status: Accepted Year Published: 2015 Citation: Dong, X. 2015. How to put plant root uptake into a soil water flow model. F1000Research (method paper)
  • Type: Conference Papers and Presentations Status: Accepted Year Published: 2015 Citation: Dong, X., Xu, W., Speer, B., Zhang, Y., Christman, J., and Leskovar, D.I. Can Irrigation Timing Ameliorate High Night Temperature Stress on Corn? ASA-CSSA-SSSA Annual Meeting, Minneapolis, MN, Nov. 15-18, 2015.
  • Type: Conference Papers and Presentations Status: Accepted Year Published: 2015 Citation: Dong, X., Speer, B., Zhang, Y., Hathcoat, D., Ibrahim, A.M.H., Neely, C.B., Xue, Q., Marek, T., Rudd, J.C., and Leskovar D.I. Cultivar-Irrigation Interactions in Shoot/Root Traits of 15 Wheat Varieties in Wintergarden Region. ASA-CSSA-SSSA Annual Meeting, Minneapolis, MN, Nov. 15-18, 2015.
  • Type: Conference Papers and Presentations Status: Accepted Year Published: 2015 Citation: Morgan, C.L.S. , Bell, J.M., DeLaune, P.B., Dong, X., Lewis, K.L., and Foster, J.L. Agronomic Management Strategies in Texas: Securing Soil and Improving the Efficiency of Water Use. ASA-CSSA-SSSA Annual Meeting, Minneapolis, MN, Nov. 15-18, 2015.
  • Type: Conference Papers and Presentations Status: Accepted Year Published: 2015 Citation: Zhang, Y., Hou, M., Xue, H., Liu, L., Sun, H., Dong, X., and Li, C. Using photochemical reflectance index and solar-induced fluorescence to assess cotton photosynthesis under water-deficit stress. ASA-CSSA-SSSA Annual Meeting, Minneapolis, MN, Nov. 15-18, 2015.
  • Type: Conference Papers and Presentations Status: Accepted Year Published: 2015 Citation: Zhang, Y., Dong, X., Speer, B., Leskovar, D. Leaf gas exchange and water use of two cotton varieties under different irrigation regimes. The 27th Annual Conference of Texas Plant Protection Association. Dec. 8-9, 2015. Bryan, TX.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2015 Citation: Dong, X., Jones, A., Speer, B., Cothren, J.T., and Leskovar, D.I. 2015. Leaf stomatal conductance, transpiration and leaf area growth patterns of four cotton varieties under different irrigation regimes in southern Texas. The Beltwide National Cotton Conference, January 5-7, 2015. San Antonio, TX.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2015 Citation: Dong, X. Root distribution and its representation for quantifying plant water uptake: An applied perspective. The 2015 Annual Meeting of ASHS New Orleans, Louisiana. August 4-7, 2015. (Invited)


Progress 02/03/14 to 09/30/14

Outputs
Target Audience: During this reporting period, X. Dong interacted with colleagues both in the Texas A&M University system and at various professional meeings/conferences, regional and national. He supervised summer student workers who helped me carry out field work. He also communicated with agricultural extension agents and local farmers to better understand the emerging issues in crop production. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Under this project, one full-time research technician and two student workers were trained to carry out various field and lab experiments, including field plot layout, equipment use, data collection and sample processing. How have the results been disseminated to communities of interest? The research reuslts were summarized as oral presentations (2 abstracts) to the joint annual meeting of American Society of Agronomy, Crop Science Society of America and Soil Science Society of America to be held in Long Beach, California, November 2-5, 2014. One abstract on cotton water use was accepted by the Beltwide Cotton Conference to be held in San Antonio, January 5-7, 2015. X. Dong also delivered presentations to the Annual Wheat-Vegetable Crops Field Day, which was held at the Texas A&M AgriLife Rsearch - Uvalde, April 23, 2014. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? This project will have impacts on changing grower's management decisions on more efficient use of limited water for crop production. This will be accomplished by collecting data on crop traits related to water use and by accurately determine crop water use and produciton under various management and climate scenarios. Goal1. In this first year of the project, we established field trials of three major crops (corn, cotton and wheat) in oder to collect needed data. The variables to be measured were mostly at field plot scale, but it turned out to be very time consuming to obtain quality data of shoot and root traits. This motivated us to build a push-wheel sensing cart for monitoring crop canopy temperature and biomass/hight growth dynamics under field conditions. This sensing cart to be put in use next growing season. Here we report three experiments in which we measured crop traits under field management conditions. (a) Corn experiment with biological soil amendment application to increase water use efficiency. In a center-pivot irrigated field, corn (Dekalb 6469) was planted March 20, 2014 in 40-inch row space. Two rows of corn were treated with soil amendment Ag1000 TM (bacteria and fungi as active ingredients) and two nearby rows were used as controls. The Ag1000 TM solution was applied in a 40 ft long strip with a rate of 10 gallons/acre, once every two weeks, started two weeks after emergence. Leaf photosynthesis and leaf orientation was measured three times during mid-days, and roots of 72 plants were excavated to count crown root number. Although there was no significant difference between Ag1000-treated and contorl plants in root number and grain yleld, the Ag1000-treatd plant used water 7-10% more efficient than the control plants, and the leaves in the former had more vertical orientation than those of the latter. Thus, Ag1000 soil amendment has the potentail water saving benefits. (b) Water use characteristics of four cotton varieties under irrigated conditions in southwest Texas. Four varieties of cotton (PHY499 WRF, DP1044 B2RF, FM1944 GLB2 and DP0935 B2RF) were planted in a center pivot field under three different levels of irrigation (100%, 75% and 50% of crop evapotranspiration) in a factorial design. Both variety and irrigation level were replicated twice. Results show a significant effect of irrigation on cotton yield (p=0.001), while variety effect was not significant (p=0.3). At 50% and 100% irrigation levels, the yield of seed cotton increased in the following order: FM1944 (2149 and 2750 lbs/acre, respectively), PHY499 (2242 and 2817 lbs/acre), DP0935 (2268 and 2878 lbs/acre) and DP1044 (2533 and 2966 lbs/acre). Leaf gas exchange rate, leaf area index and sap flow rate were measured during the experiment. Of the four varieties, PHY499 and DP1044 were selected to measure sap flow. From August 4 to 10, the average sap daily flow rate under 50% irrigation was 2.1 and 1.27 kg/day/m2 (leaf area), respectively, for PHY499 and DP1044. Following a heavy rain in August 19, 2014 (1.5 in.), the corresponding sap flow rate for the period of August 19 to 25 increased to 4.3 and 2.7 kg/day/m2, respectively. Data of stomatal conductance also indicated that DP1044 shut down its water use earlier than PHY499 in August. It is likely that overall water use efficiency of DP1044 may be higher than PHY499. (c) Winter wheat root traits in relation to grain yield under different irrigation conditions. In November 2013, fifteen winter wheat varieties were planted under three levels of irrigaiton (full irrigation, 75% and 50% full irrigation) in a conventionally tilled, center pivot irrigated field. The fifiteen varieties were: Armour, Billings, Cedar, Coronado, Doans, Duster, Fannin, Fuller, Gallagher, Santa Fe, Shocker, TAM112, TAM304, TAM305, TAM401. Upon harvest in May 23, 2014 and the measurement of yield, soil cores were collected to measure root traits. Each soil core was sub-divided into 5 segments at 20 cm intervals and washed for roots using an elutriation system. The roots were kept in 20% ethanol solution before being measured using the WinRHIZO software for morphological traits. No signifcnat effect of variety or irrigation was found in root diameter and specific root length (leng per unit mass). However, roots were finner at intermediate soil depth of 40-60 cm than either the top (0-20 cm) and bottom (100-120 cm) layer. Under wet condtions (full irrigation and 75% full), root length density per unit soil volume was poorly correlated with grain yield (r=-0.15, p=0.6). The same correlation was much higher under dry condition (50% irrigation, r=0.39, p=0.15). Under 50% irrigation, the highest yield was measured in Shocker (44 bu/ac), which also had the highest root length density (2.4 cm/cm3). On the contrary, under the same 50% irrigation, a local popular variety Fannin yielded low (37 bu/ac) and also had a low root density (1.7 cm/cm3). Currently due to shortage of water, more acres of wheat are planted in southwest Texas, particularly under limited irrigation. Thus superioir root traits will be important in variety selection and breeding efforts. However, grain yield is influenced by multiple factors and traits. Further work will emphasize both root and shoot traits by use of high throughput phenotyping. Goal 2. The objective of quantifying transpiration and crop water use will be addressed by using a simplified root water uptake model. One major effort is to estimate hydraulic functions pertinent to soil types in Uvalde of Texas. For this, we had collected 24 composite soil samples representing the Uvalde silty clay loam and tested for textural composition and bulk density. Also, we developed computer code to automatically extract soil water relations parameters based on easily measured soil textural data. We are measuring the soil infiltration rate and hydraulic conductivity under field conditions, but at this time we do not have reportable results yet. Goal 3. X. Dong participated in the 2014 DSSAT Training Workshop held at Griffin, Georgia, USA from May 19 to 24, 2014, and gained technical knowledge of applying the DSSAT modeling system to local conditions using different cropping system models and soil-climate information. Research is in progress to include into the crop system models the local soil/crop data and historical wheather data of Uvalde region. At the same time, we analyzed data from past 5 years' (2009-2013) research conducted at the Uvalde research center to investigate the effects of soil tillage and irrigation on cotton yield. A 12-acre cotton field (a quarter of a center pivot irrigated field) was divided into three sections radially for three irrigation treatments (100% irrigation based on potential evapotranspiration and crop coefficient; 70% reduced irrigation during early crop stage; and 70% of full irrigation throughout the crop season). The early reduced irrigation was applied during the early growth stage (prior to flowering). The cotton variety used was DP 935. Across the five years, irrigation had significant effect on cotton yield (p=0.027), with production from the 70% deficit irrigation treatment being lower than the full irrigation and the early reduced irigation treatment (2277 ± 106 kg/ha, 2895 ± 110 kg/ha and 2957 ± 93 kg/ha). The effect of tillage was not significant (p=0.27), although the yield from the strip-tilled plots was numerically higher than that from the conventional tillage (2789 ±90 kg/ha vs. 2631 ± 95 kg/ha). The results show that a 10% reduction in early irrigation water use resulted in similar or higher yields as compared to full irrigation. This demonstrated the value of regulated deficit irrigation in crop management.

Publications

  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Dong, X., Leskovar, D., Crosby, K., and Marek, T. (2014). Quantifying crop water use in arid and semi-arid regions: Opportunities based on soil-plant water relations. Journal of Arid Land Studies, 24-1: 141-144.
  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Sun, Y., Gu, L., Dickinson, R.E., Pallardy, S.G., Baker, J., Cao, Y., DaMatta, F.M., Dong, X., Ellsworth, D., Van Goethem, D., Jensen, A.M., Law, B.E., Loos, R., Martins, S.C.V., Norby, R.J., Weston, D., Winter, K. (2014). Effects of mesophyll conductance on fundamental photosynthetic parameters and their relationships estimated from leaf gas exchange measurements. Plant, Cell and Environment, 37: 978-994.
  • Type: Conference Papers and Presentations Status: Accepted Year Published: 2014 Citation: Dong, X., Forbes, D., Speer, B., Shallock, J., Rowland, D., and Morgan, C. (2014). Effects of tillage and reduced irrigation on cotton yield in southern Texas. The 2014 Annual Meeting of ASA-CSSA-SSSA, Long Beach, CA. November 2-5, 2014.
  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Dong, X., Patton, J., Gu, L., Wang, J.Z., and Patton, B. (2014). Leaf photosynthesis and plant competitive success in a mixed-grass prairie: With reference to exotic grasses invasion. Journal of Ecosystem and Ecography, 4: 152. doi: 10.4172/2157-7625.1000152.
  • Type: Journal Articles Status: Accepted Year Published: 2014 Citation: Dong, X., and Patton, B.D. (2014). Predicting soil water retention curves based on particle-size distribution using a Minitab macro. African Journal of Soil Science, Accepted.
  • Type: Conference Papers and Presentations Status: Accepted Year Published: 2014 Citation: Dong, X., Leskovar, D., Pierson, B., Pierson L.S., Sharma, S.P., Gibby, A., and Pape, G. (2014). Ag1000 soil amendment increased root growth and intrinsic leaf water use efficiency in corn. The 2014 Annual Meeting of ASA-CSSA-SSSA, Long Beach, CA. November 2-5, 2014.
  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Zhang, Z.-S., Chen, Y.-L., Xu, B.-X., Huang, L., Tan, H.-J., and Dong, X.-J. (2014). Topographic differentiations of biological soil crusts and hydraulic properties in fixed sand dunes, Tengger Desert. Journal of Arid Land, doi: 10.1007/s40333-014-0048-y