Progress 01/01/18 to 12/11/21
Outputs
Target Audience: Fellow research, extension, NGO, and industry scientists who have a stake in sustainable farming systems. Undergraduate and graduate students Producers who are wanting to decrease their reliance on fertilizer and herbicide inputs. The general public who are concerned about environmentally unsustainable farming techniques. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Training activities: 1) This project trained 3 graduate students: one at Emory University and two at The University of Georgia. Two of the students Emory University and one from The University of Georgia) secured professional appointments in their respective disciplines. One student at the University of Georgia is completing his PhD in agricultural bioinformaticsl. How have the results been disseminated to communities of interest?Results have been disseminated using stakeholder-specific means. These are categorized as: Fellow research, extension, NGO, and industry scientists who have a stake in sustainable farming systems. Research results were published in peer-reviewed journals to reach a general scientific audience. In addition, results were disseminated at National and International professional meetings to provide opportunities for critique, in-depth interaction on specifics of methodologies and where the technology is applicable, and how it will impact future research and outreach efforts. Undergraduate and graduate students. Students were exposed to the theory of the living mulch system in crop and soil sciences classes, followed by field visits and laboratory exercises to illustrate how the living mulch system works, and examine the soil physicaland chemical properties imparted by the living mulch system. Producers who are wanting to decrease their reliance on fertilizer and herbicide inputs. Yearly field days were conducted at the J. Phil Campbell Research and Education Center in which producers could visit the research site, get the most recent research results, and ask questions about their specific requirements for technology transfer and implementation. The general public who are concerned about environmentally unsustainable farming techniques. An annual "Corn Boil" was held at the J. Phil Campbell Research and Education Center in which the public was invited. This is an event in which the public is invited to take tours of the research programs and learn about the reasons for conducting the research,the results of the experiments, and why the experiments are relevant to them.The Corn Boil concluded witha lunch in which hot dogs, homemade baked beans, watermelon, andExperiment Station-grown sweet corn was served. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
1) Soils in the LM (white clover) system had lower lime buffering capacity and greater pH, base saturation, cation exchange capacity (CEC), Ca, K2O, Mg, P2O5 , and total organic C concentrations than other treatments. Soil NH3 and NO3 had seasonal fluctuations associated with mineral N fertilizer and were lower in the LM treatment. After 3 yr, the soil bulk density was lower and porosity, water infiltration, and labile C were greater in surface soils from the LM treatment than in the surface soils of the other treatments. Use of a perennial LM cover crops expedited soil health regeneration compared to other treatments. 2)The mean total N provided from the cover crops was 145, 105, and 25 kg ha−1 in the LM, Crimson clover (CC), and cereal rye (CR) cover crop systems, respectively. Water uptake by the LM reduced soil water content, soil N availability, N uptake, and plant-available N (PAN) compared with the CC and CR cover crop systems. Average grain yield was 10.4, 13.3, and 13.0 Mg ha−1 for the LM, CC, and CR cover crop systems, respectively. Nitrogen internal utilization efficiency was not different among systems, but fertilizer N partial nutrient balance and partial factor productivity was greatest for LM and least for CR. Overall, the LM system had lower soil N availability, grain yield, and PAN, but it supplied a significant amount of legume N to corn and minimized the need for mineral N. We concluded that success of the LM system is dependent on N mineralization of the white clover residue and that yearly weather variation significantly affects mineralization of cover crop residues and PAN. Using 15N radioisotopes we were able to demonstrate that approximately 160 kg/ha of N was released from the white clover, and greater than 80% of the released nitrogen from the living mulch clover was taken up by the corn. 3) Mean soil CO2 and N2O fluxes (159.7 kg ha−1 d−1 and 0.027 kg N ha−1 d−1, respectively) observed in LM plots exceeded those from other treatments. Soil temperature, moisture, potentially mineralizable nitrogen (N), and nitrate partially explained these differences. Much of the CO2 from the living mulch was associated with plant respiration. Mean soil NH3 emissions were greater in LM (0.089 kg N ha−1 d−1) compared with no cover crop (0.038 kg N ha−1 d−1). Increased N2O and NH3 fluxes could be from release of N from decomposition of clover and from release of N into the soil as the corn shades the clover. Although LM plots did not reduce trace gas emissions, labile carbon content was at least 100 mg kg−1 greater than other treatments after 2 yr, improving soil health.
Publications
- Type:
Journal Articles
Status:
Other
Year Published:
2021
Citation:
Hanxia Li, Nicholas Hill, Jason Wallace. 202x. Living mulch fosters a more diverse and balanced bacterial community in corn production.
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Progress 01/01/20 to 12/31/20
Outputs
Target Audience:The targeted audiences for this project include professional peers, undergraduate and graduate students, producers, industry stakeholders. Changes/Problems:The major problems we encountered in our research effort were a) weed control during cover crop establishment, and b) perennial weed infestation as age of the LM system increased. Control of annual weeds during establishment was addressed and corrected by using various chemistries of herbicides. Subsequent research is investigating the ecology and control of perennial weeds. What opportunities for training and professional development has the project provided?Two graduate students and two research technicians were assigned to conduct research on this project. Students were required to attend professional meetings (national and regional) and present their results to their professional peers. Project investigators also attended meetings and were able to share the results with peers on formal and informal meetings. How have the results been disseminated to communities of interest?1. Annual field days were conducted where scientists, graduate students, industry and community stakeholders attended. Normal attendance of these annual events ranged between 200 and 300 individuals. 2. Undergraduate and Graduate classes participated in field trips to the research sites to provide an experiential learning opportunity for the student population at UGA. 3. Industry and government (U.S congresspeople; Georgia State Representatives; Georgia Commissioner of Agriculture) stakeholders attended a one-day presentation of ongoing research at the University of Georgia J. Phil Campbell Research and Education Center. 4. Local and industry related news media showcased the living mulch research in print, radio, and television media. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
1) Soils in the LM (white clover) system had lower lime buffering capacity and greater pH, base saturation, cation exchange capacity (CEC), Ca, K2O, Mg, P2O5, and total organic C concentrations than other treatments. Soil NH3and NO3had seasonal fluctuations associated with mineral N fertilizer and were lower in the LM treatment. After 3yr, the soil bulk density was lower and porosity, water infiltration, and labile C were greater in surface soils from the LM treatment than in the surface soils of the other treatments. Use of a perennial LM cover crops expedited soil health regeneration compared to othertreatments. 2)The mean total N provided from the cover crops was 145, 105, and 25 kg ha−1in the LM, Crimson clover (CC), and cereal rye (CR) cover crop systems, respectively. Water uptake by the LM reduced soil water content, soil N availability, N uptake, and plant-available N (PAN) compared with the CC and CR cover crop systems. Average grain yield was 10.4, 13.3, and 13.0 Mg ha−1for the LM, CC, and CR cover crop systems, respectively. Nitrogen internal utilization efficiency was not different among systems, but fertilizer N partial nutrient balance and partial factor productivity was greatest for LM and least for CR. Overall, the LM system had lower soil N availability, grain yield, and PAN, but it supplied a significant amount of legume N to corn and minimized the need for mineral N. We concluded that success of the LM system is dependent on N mineralization of the white clover residue and that yearly weather variation significantly affects mineralization of cover crop residues and PAN. 3) Mean soil CO2and N2O fluxes (159.7 kg ha−1d−1and 0.027 kg N ha−1d−1, respectively) observed in LM plots exceeded those from other treatments. Soil temperature, moisture, potentially mineralizable nitrogen (N), and nitrate partially explained these differences. Mean soil NH3emissions were greater in LM (0.089 kg N ha−1d−1) compared with no cover crop (0.038 kg N ha−1d−1). Increased N2O and NH3fluxes could be from release of N from decomposition of clover and from release of N into the soil as the corn shades the clover. Although LM plots did not reduce trace gas emissions, labile carbon content was at least 100 mg kg−1greater than other treatments after 2 yr, improving soil health.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2021
Citation:
Peters, S.J., Saikawa, E., Markewitz, D., Sutter, L., Avramov, A., Sanders, Z.P., Yosen, B., Wakabayashi, K., Martin, G., Andrews, J.S. and Hill, N.S., 2020. Soil trace gas fluxes in living mulch and conventional agricultural systems (Vol. 49, No. 2, pp. 268-280).
Hill, N.S., Levi, M., Basinger, N., Thompson, A., Cabrera, M., Wallace, J., Saikawa, E., Avramov, A. and Mullican, J., White clover living mulch enhances soil health versus annual cover crops. Agronomy Journal.doi.org/10.1002/agj2.20768
Basinger, N.T. and Hill, N.S., Establishing white clover (Trifolium repens) as a living mulch: weed control and herbicide tolerance. Weed Technology, pp.1-28.
Andrews, J.S., Sanders, Z.P., Cabrera, M.L., Saha, U.K. and Hill, N.S., 2018. Nitrogen dynamics in living mulch and annual cover crop corn production systems. Agronomy Journal, 110(4), pp.1309-1317.
Andrews, J.S., Sanders, Z.P., Cabrera, M.L., Hill, N.S. and Radcliffe, D.E., 2020. Simulated nitrate leaching in annually cover cropped and perennial living mulch corn production systems. Journal of Soil and Water Conservation, 75(1), pp.91-102.
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Progress 01/01/19 to 12/31/19
Outputs
Target Audience:The living mulch system of producing crops is dependent upon providing conditions conducive for row crops and white clover (the living mulch) to cohabitate. The system is a radical departure from traditional row-crop production and is, therefore, expected to require signicant effort to transfer the technology from the laboratory/experiment stations to the end users. Four distinct audiences were targeted in this past year. First was the scientific community via publications of research results from other living mulch projects to provide background and reasoning for the current research effort. The research findings were published in the Agronomy Journal in an effort to educate peers as to the agronomic and environmental significance of the living mulch project. Presentations were also made to the scientific community at regional and national meetings in order to provide the most up-to-date research findings. The second audience was producers who have demonstrated that they are technology adopters. Inasmuch as row crop production is a novel method of farming, it will require a uniqe set of producers who are willing to try new production systems and follow directions during implementation to achieve the greatest likelihood for success., This was conducted by holding meetings at County extension offices and field days to provide both theory and first-hand experience observing the living mulch system. Producer-targeted field days were designed to explain how management variables will affect how the plant species (clover and row crop) respond to competition from one another when agronomic variables (row spacing, population density, irrigation, etc.) vary. A third targeted audience was graduate and undergraduate students. Our students are well versed in the theoretical aspects of crop production but a diminishing pool are from farm backgrounds. Field trips to the research plots demonstrated the difference between productoin practices when crops are grown in the living mulch system, winter annual cover crops, and no cover crop scenarios. Two undergraduate and two graduate students students worked on the research project and experience the practice first-hand. The fourth targeted audience was citizen groups. These groups have an interest in agriculture and/or the environmental consequences of agricultural practices. A field day was conducted to provide a hands-on experience of the living mulch production system and was complemented with data from the experiments illustrating the benefit to soil health, the ecosystem services, and economic advantage producers. This holistic approach to community education was well received and highlighted in local newspapers. Changes/Problems:none What opportunities for training and professional development has the project provided?Objective 1. One graduate student from the University of Georgia gathered and conducgted water infiltration measurements, ran SOM and POX analyses on the soil samples, and assisted with statistical analysis.. Objective 2. One graduate student from the University of Georgia conducted this experiment, including labeling clover with 15N, harvesting and applying labeled clover to research plots, monitoring soil and clover residue moisture, and sampling clover and corn tissues, quantifiying corn and clover biomass, sampling soils, and preparing samples for analysis. Objective 3. One graduate student from Emory University (Atlanta) assumed leadership on making soil gaseous measurements. A second graduate student from the University of Georgia provided logistical assistance. How have the results been disseminated to communities of interest?Both students presented research findings from objectives 2 and 3 at professional meetings. The PI from the University of Georgia presented the findings from Objective 1 to one international scientific meeting and one national scientific meeting. Four field day events were held at two locations in Georgiaand one location in Alabama to disseminate the research findings to rural and urban stakeholders. What do you plan to do during the next reporting period to accomplish the goals?Objective 1. Submit a research article on the effect of cover crops and physical and chemical properties of soil (likely to Agronomy J. or J.SSSA). Objective 2. Complete 15N siotopic analysis of samples and conduct statistical analysis on all data for this objective. Objective 3. Finish carbon equivalent calculations for each cover crop system.; Model potential impact of each cover crop production system on global warming.
Impacts
What was accomplished under these goals?
Objective 1. Analysis of variance indicated there were significant main treatment effects (cover crop, sampling date within year, and year) differences on most soil chemical attributes. Cover crops affected temporal changes in soil chemical composition for lime buffering capacity, pH, base saturation, CEC, Ca, K, Mg, P, NH3, NO3, total organic carbon (TOC), total soil N, and labile C, but not Fe or soluble salts. Generally speaking, pH, base saturation, CEC, Ca, K, Mg, P, TOC, and total N were greater among the legume cover crop treatments (crimson clover and white clover) than treatments of no cover crop or cereal rye. Lime buffering capacity was greatest when no cover crop was used but not different among the other cover crop treatments. There were interactions among cover crop and sampling date treatments for NH3 and NO3, and between cover crop and year for total organic carbon. Soil NH3 and NO3 was greatest after top dressing with mineral N in the no cover crop and cereal rye treatments, but were relatively unchanged regardless of sampling date in the crimson clover and white clover treatments. Soil NO3 was not different regardless of cover crop treatment early in the growing season, but was least in the white clover cover crop treatment during mid-season. There were no differences in soil NO3 among cover crop treatments later in the growing season. Total organic carbon in the soil was greatest in the white clover cover crop treatment in all years except 2016, when drought occurred. There were no differences in TOC among cover crop treatments in 2016. TOC in the white cover treatments increased as years progressed, but there were no differences in TOC from 2015 to 2018 in the other cover crop treatments. Bulk density decreased in treatments using white clover as a cover crop. Soil bulk density was not different among the other cover crop treatments. Porosity and saturated surface water infiltration rates increased in the white clover cover crop treatment but was not different among the other cover crop treatments. Soil water holding capacity was not affected by cover crop treatment, indicating that increased porosity in the white clover treatment was due to macropores. Objective 2. Total decomposition of the white clover residue within herbicide treated strips and release of 15N labeled N from the residue occurred within 60 days of planting the corn in 2018. The labeled N was taken up (primarily) by seedling corn, with minimal labeled N found in the living (and competing white clover) or in the soil. Labeled N content of the corn was inversely related to the labeled N remaining in the decomposing clover (ie. as N was released from the residue it was taken up by the corn). Approximately 97% of the labeled N was found in the corn at the end of the growing season. The data suggest approximately 33 of the 35 kg/ha of N released from herbicide treated clover strips is available and taken up by seedling corn. A complementary study investigating N rates applied as starter fertilizer indicated no yield differences between 20 or 40 kg/ha N was added at planting. The experiments combined indicate that 20 kg/ha starter N was sufficient to meet the recommended 50 kg/ha N at corn planting. This experiment was repeated in 2019 but isotopic analysis of plant and soil samples has not been completed at the time this report was written. Objective 3. Total soil CO2 emission was greatest in the white cover treatment. About 40% of the CO2 emission was autotrophic from white clover root respiration. Still, the amount of CO2 emission from the white clover treatments was greater than the other cover crop treatments, likely due to increased labile C in the soil. NOx and NH3 gas emission was slightly greater in the white clover treatment than in other cover crops. A total carbon equivalent assessment is being conducted to determine the impact of drastically reduced mineral N use vs. the slightly higher soil GHG emissions.
Publications
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Progress 01/01/18 to 12/31/18
Outputs
Target Audience:The living mulch system of producing crops is dependent upon providing conditions conducivefor row crops and white clover (the living mulch) to cohabitate. The system is a radical departure from traditional row-crop production and is, therefore, expected to require signicant effort to transfer the technology from the laboratory/experiment stations to the end users. Four distinct audiences were targeted in this past year. First was the scientific community via publications of research results from other living mulch projects to provide background and reasoning for the current research effort. The research findings were published in the Agronomy Journal in an effort to educate peers as to the agronomic and environmental significance of the living mulch project. Presentations were also made to the scientific community at regional and national meetings in order to provide the most up-to-date research findings. The second audience was producers who have demonstrated that they are technology adopters. Inasmuch as row crop production is a novel method of farming, it will require a uniqe set of producers who are willing to try new production systemsand follow directions during implementation to achieve the greatest likelihood for success., This was conducted by holding meetings at County extension offices and field days to provide both theory and first-hand experience observing the living mulch system. Producer-targeted field days were designed to explain how management variables will affect how the plant species (clover and row crop)respond to competition from one another when agronomic variables (row spacing, population density, irrigation, etc.) vary. A third targeted audience was graduate and undergraduate students. Our students are well versed in the theoretical aspects of crop production but a diminishing pool are from farm backgrounds. Field trips to the research plots demonstrated the difference between productoin practices when crops are grown in the living mulch system, winter annual cover crops, and no cover crop scenarios. Two undergraduate and two graduate students studentsworked on the research projectand experience the practice first-hand. The fourth targeted audience was citizen groups. These groups have an interest in agriculture and/or the environmental consequences of agricultural practices. A field day was conducted to provide a hands-on experience of the living mulch production system and was complemented with data from the experiments illustrating the benefit to soil health, the ecosystem services, and economic advantage producers. This holistic approach to community education was well received and highlighted in local newspapers. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Objective 1. One graduate student from the University of Georgia gatheredand conducgted water infiltration measurements, ran SOM and POXanalyses on the soil samples, and assisted with statistical analysis.. Objective 2. One graduate student from the University of Georgia conducted this experiment, including labeling clover with 15N, harvesting and applying labeled clover to research plots, monitoring soil and clover residue moisture, and sampling clover and corn tissues, quantifiying corn and clover biomass, sampling soils, and preparing samples for analysis. Objective 3. One graduate student from Emory University (Atlanta) assumed leadership on making soil gaseous measurements. A second graduate student from the University of Georgia provided logistical assistance. Visiting and prospective graduate students from China, South Korea, and the United States visited the research plots on a regular basis. How have the results been disseminated to communities of interest?Updated information was presented at the American Society of Agronomy National meetings held in Baltimore, MD on November 4, 2018. What do you plan to do during the next reporting period to accomplish the goals?Objective 1. We will finish analyzing the soil samples for aforementioned response variables and conduct statistical analyes for each. Objective 2. Statistical analysis we be conducted on recovery of 15N in corn and clover to determine the competitiveness of each for minearalized clover N. The experiment will be repeated in thesummer of 2019 to validate the results from 2018. Objective 3. Soil gaseous emission data will be used to model the potential impact of each cover crop production system on global warming.
Impacts
What was accomplished under these goals?
Objective 1.A fourth year of continuous production of corn in the white clover living mulch (LM), cereal rye, crimson clover, and no cover crop systems was completed. Soils samples taken at the v4, v12, and R1 stages of corn development were sorted. Organic matter (ignition=OM) and permanganate oxidizable carbon (POX) were quantified in each sample There were significant cover crop treatment effects for both OM and POX with the living mulch being the greatest for both response variables and the no cover crop the least for each. Crimson clover had less POX than LMbut was greater than cereal rye. Crimson and LM had similar OM, but both were greater than cereal rye, which was greater than the no cover crop treatment. Bulk density and water infiltration was greatest for LM, follwed by cereal rye and crimson clover, and least for the no cover crop treatment. All soil samples are currently being analyzed for N, P, K, pH, CEC, EC, SOC, SON, and mineral N. Objective 2. Competition between corn and clover for N released in the LM system was tested using a 15N study. A stand of white clover was labeled using 15N ammonium sulfate applied in granular form 1 month prior to harvest. Harvested clover was used to either replace clover in the LM system, placed as a mulch layer over the row of corn in a no-cover crop plot, and compared to unlabeled systems of each treatment. Corn and clover samples were gathered on a weekly basis until all clover residue had been mineralized. Dry weights of each were recorded. Samples were submitted to the UGA isotopic analytical lab for analysis and results are expected in the near future. Objective 3. Soil gasseous N and CO2 emissions were measured using a Picarro in-field gas analyzer. Three chambers were placed in each plot and measured using both open and closed chamber methods weekly beginning in March and ending in August, 2018. Data are in the process of being analyzed and interpreted.
Publications
- Type:
Journal Articles
Status:
Accepted
Year Published:
2018
Citation:
Sanders, Z.P. J.S. Andrews, and N.S. Hill. 2018. Water use efficiency in living mulch and annual cover crop corn production systems. Agron. J. 110:1128-1135.
91. Andrews, J.S., Z.P. Sanders, M. Cabrera, U.K. Saha, and N.S. Hill. 2018. Nitrogen dynamics in living mulch and annual cover crop corn production systems. Agron. J. 110:1309-1317.
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