Location: Soil Management Research
2017 Annual Report
Objectives
Objective 1: Evaluate conservation practices adapted for use in short-growing seasons to enhance soil quality, improve nutrient use efficiency and sustain agronomic productivity.
Objective 2: Integrate soil and crop management practices that enable sustainable, climate-resilient agriculture for the Upper Midwest.
Approach
Two objectives are being addressed using a temporally-stratified and multi-faceted approach to select, evaluate and initiate integrated conservation practices for regional suitability. Data from seven long-term studies are providing the foundation for evaluating individual and integrated practices using statistical modeling and management assessment indices. These studies were designed with several types of conservation practices including tillage, conversion of perennials, including perennial in extended rotations, addition of cover crops and impacts of variable stover harvest rates. Each experiment study was set out as a randomized complete block or as a split plot – with randomized complete block within the spilt. All have four replications of each treatment. These long-term studies have SOC and corn grain yield data in common; so those variables will be used if conversion to 1) conservation tillage; 2) perennial grasses; or 3) including a winter rye cover crop increase SOC and if returning all crop biomass increases SOC compared harvesting stover.
Soil quality assessment indices approach: Assessment one tests the hypothesis that soil quality assessment scores will be greater (indicting improved soil quality) following multiple years of deploying a conservation practice compared to business as usual. Assessment scores at two (or more) time points from existing datasets from the long term studies will be used to determine if soil quality appears to be aggrading, degrading or remaining the same over time. A second assessment will be made using data collected form a common future data set from studies that will have been in place at least 10 years compare treatments lacking conservation to treatments with one or more conservation practices deployed. Comparisons of management strategies will be made using a mixed model ANOVA procedure to assess soil scores among treatments.
The ability of annual rye grass or forage radish to improve nutrient use efficiency in corn is being addressed. The null-hypotheses for this experiment are that yield, and N use of corn grown following cover crops (annual rye grass or forage radish) will not differ from corn grown without a preceding cover crop, and that the nitrogen fertilizer requirements will be similar for corn following wheat with or without a cover crop. Treatments were arranged in a replicated, randomized complete block design, which was blocked by field location and replicated four times. Cover crop shoot and root biomass, crop yield and N uptake, and soil N levels will be measured. Statistical analyses will analyze linear and quadratic effects of N treatments. Using a mixed-model ANOVA, cover crop will be treated as a fixed effect, N-rates as a continuous variable, and replication (within a site year) and site-year as random effects.
Progress Report
Objective 1. Progress continues towards establishing better understanding of conservation practices that enhance soil quality, improve nutrient-use efficiency and sustain agronomic productivity. Within this fiscal year, on-going field research plots were managed, monitored, and plant and soil samples taken and processed for planned analyses. Data from these on-going experiments contributed to Goal 1.1 to evaluate conservation practices from long-term studies. Under this goal, substantial progress was made to evaluate long-term use of strip-tillage, diverse four-year rotations and/or organic management effects on soil health, long-term yield trends, and soil carbon (See Accomplishment 1). Substantial progress was made specifically to evaluate soil carbon and nitrogen balance in this system (See milestones for Obj. 1.1). Field evaluation of a cover crop nitrogen study was continued through this year. In the fall, final yields will be taken to evaluate the impact of cover crop use and nitrogen application rates (See milestone for Obj. 1.2). To expand on the cover crop nitrogen experiment, two new field experiments were established. These experiments are specifically designed to evaluate cover crop variety options and planting methods, e.g., interseeding at various stages of crop development. Additionally, evaluation of nitrogen mineralization from fall 2016 seeded cover crops is in progress.
Objective 2. Substantial progress was made to evaluate soil quality assessment scores from compiled data of long-term studies (See milestones for Obj. 2). Data from three long-term studies has been organized for conducting a soil quality assessment with the Soil Management Assessment Framework (SMAF) and calculating corresponding soil quality index scores. Statistical analyses and manuscript preparation are on-going.
Substantial progress has been made to meet the overall project objective of integrating our unit results into Resilient Economic Agricultural Practices (REAP) and Greenhouse gas Reduction through Carbon Enhancement network (GRACEnet) and Long-Term Agroecosystem research (LTAR), which enables a whole agroecosystem, multi-location, multi-faceted, long-term approach to develop sustainable, intensified agricultural systems that feed people and protect the planet. Datasets from five experiments were contributed to the GRACEnet and REAP programs, which collectively represents 48 site years of soil, yield and management data, plus greenhouse gas emission data. Additionally, contributions were made to a nationwide effort to improve soil quality and soil health assessments. Contributions were also made to establish a nitrogen-use database for the newly organized Nutrient Use and Outcome Network (NUOnet). Scientists at Morris, Minnesota, contributed communication management and development of a data entry template specific to the NUOnet database, which is based on the GRACEnet/REAP data entry template. ARS scientists at Morris, Minnesota, contributed to the efforts customizing the GRACEnet/REAP data entry template to accommodate unique data collected and shared by the Agricultural Antibiotic Resistance (AgAR) groups and by Soil Biology.
Substantial progress was made on the Long-Term Agricultural Research (LTAR) subordinate projects related to objective 1, understanding of conservation practices that enhance soil quality, improve nutrient-use efficiency and sustain agronomic productivity. An agreement was signed between ARS and a local farmer, whereby ARS researchers will have access to 80 acres of land to conduct planned data collection and monitoring of soil-plant-atmosphere continuum. Two covariance towers were installed and instrumented to collect ecosystem gas exchange data, additional meteorological and soils data are being collected. Phenological data for growing crops is being captured using small unmanned airplane system equipped with sensors and acquiring images that provide information related to crop health. The on-farm data is complemented with Swan Lake Research Farm plot-scale phenological data, which is part of the National Phenocam Network. Weather data is automatically collected and transferred to the National Agricultural Library in near-real time. A crop phenocam, installed October 2, 2015, at the Swan Lake Research Farm, continues in operation and provides red-blue-green spectrum and infra-red images twice per hour during daylight hours, 24x7, year round, to the National Agricultural Library, National Phenocam Network. Two additional phenocams are planned for installation at the on-farm research site.
Accomplishments
1. Demonstrated conservation strategies improve soil health and have marginal effects on crop yields. In the upper Midwest, climatic, economic and knowledge limitations contribute a low adoption rate of conservation tillage (i.e., strip tillage) and diverse crop rotations especially by risk adverse farmers. To build better information on system performance, ARS researchers at Morris, Minnesota, evaluated the impact of multiple combinations of tillage, rotation, and fertility treatments on crop yields in conventional and organic farming systems. Although overall system performance was better with conventional tillage and a two-year rotation due to higher corn grain yields in conventional systems and more effective weed control in organic systems, this long-term (9 year) evaluation demonstrated that instability in conventional corn grain prices, soil health benefits of strip-tillage, and reduced economic risk with diverse cropping practices indicate potential for adoption of these conservation strategies. This research enables scientists, land managers, and policy makers to develop and promote conservation management strategies for conventional and organic agricultural production systems.
2. Assessed corn residue harvest impacts on soil and water infiltration properties on Minnesota farms. Corn residue may be harvested for many reasons (e.g., animal feed or bedding, bioenergy) and these materials are also critical for protecting soil and hydrological properties. However, information is lacking from on-farm sites to document whether conservation tillage strategies are sufficient to protect soil resources when residues are aggressively harvested. ARS scientist from Morris, Minnesota, in collaboration with university scientists and local producers assessed the short-term effects of harvesting corn residues at on-farm experimental sites. Results of this study suggested that to protect soil and water infiltration properties from degradation all corn residue needs to remain on the soil, even if the field had little tillage disturbance. This work will aid producers, energy industry, and action agencies to balance the pros and cons of harvesting crop residues such as corn stalks for bioenergy.
Review Publications
Johnson, J.M., Strock, J.S., Tallaksen, J.E., Reese, M. 2016. Corn stover harvest changes soil hydrology and soil aggregation. Soil & Tillage Research. 161:106-115.
Weyers, S.L., Archer, D.W., Forcella, F., Gesch, R.W., Johnson, J.M. 2017. Strip-tillage reduces productivity in organically managed grain and forage cropping systems in the Upper Midwest, USA. Renewable Agriculture and Food Systems. doi: 10.1017/S1742170517000084.
Weyers, S.L., Archer, D.W., Forcella, F., Gesch, R.W., Johnson, J.M. 2017. Can reducing tillage and increasing crop diversity benefit grain and forage production? Renewable Agriculture and Food Systems. doi: 10.1017/S1742170517000187.
Johnson, J.M., Strock, J.S., Barbour, N.W., Tallaksen, J.E., Reese, M. 2017. Stover harvest impacts soil and hydrologic properties on three Minnesota farms. Soil Science Society of America Journal. 81:932-944. https://doi.org/10.2136/sssaj2017.01.0007
