Location: Agroecosystems Management Research
2020 Annual Report
Objectives
Objective 1: Quantify the effects of conventional and alternative corn-soybean based cropping systems on the factors and processes of nutrient cycling and nutrient-use efficiency. Sub-objectives: 1.1 Determine effects of conventional and alternative corn-soybean based cropping systems on soil nutrient dynamics and crop nutrient uptake and yield; and 1.2 Determine effects of organic cropping systems on soil carbon and nitrogen storage.
Objective 2: Evaluate the effects of conventional and alternative corn-soybean based cropping systems, on soil water dynamics and drainage water nutrient transport. Sub-objectives: 2.1 Determine effects of fall-planted cover crops and no-tillage within conventional and alternative corn-soybean rotations on tile flow and drainage water nutrient concentrations; and 2.2 Determine effects of organic cropping systems on water quality and soil profile water storage.
Objective 3: Determine the effects of conventional and alternative corn-soybean based cropping systems, on indicators of soil health. Sub-objectives:
3.1 Determine effects of organic cropping systems on soil health; and 3.2 Determine effects of fall-planted cover crops, relay crops, and no-tillage within conventional and alternative corn-soybean rotations on soil health.
Objective 4: Operate and maintain the Upper Mississippi River Basin Experimental Watersheds LTAR network site using technologies and practices agreed upon by the LTAR leadership. Contribute to the LTAR working groups and common experiments as resources allow. Submit relevant data with appropriate metadata to the LTAR Information Ecosystem. Goals: 4.1 Implement the LTAR Common Experiment comparing conventional (BAU) and aspirational (ASP) cropping systems and the measurement of parameters to support analysis of sustainability and ecosystem services for these cropping systems; and 4.2 Develop improved capabilities for acquiring, storing, and providing data to the LTAR Network and the larger agricultural community.
Approach
A combination of controlled experiments in the field and laboratory, tile drainage monitoring, and a variety of modeling techniques and statistical analyses will quantify the effects of 4R management (Right source, Right rate, Right time, and Right place) of nitrogen on nutrient (nitrogen, phosphorus, potassium, and sulfur) cycling in a corn-soybean system (Objective 1). This same approach will be used to determine the ability of cover crops to reduce nitrate losses (Objective 2) and maintain soil health (Objective 3) in a corn-soybean system, and the efficacy of organic cropping systems to reduce nitrate losses (Objective 2) and enhance soil health (Objective 3). We will determine how fall-planted cover crops and no-tillage within conventional and alternative corn-soybean rotations affect tile drainage water flow and nutrient concentrations, and how drainage water quality and soil profile water storage may differ in organic systems. We will use several indicators of soil health, such as aggregate stability and nitrogen mineralization potential, to compare and contrast conventional corn-soybean based cropping systems, corn-soybean based systems that include cover crops, and organic systems that include extended rotations. These comparisons are conducted using experimental plots with individual subsurface (tile) drains that allow robust measurements of hydrologic and nutrient balances. The research contributes to the Long Term Agroecosystem Research (LTAR) effort to ascertain the sustainability of and ecosystem services for conventional, i.e., business as usual (BAU), and aspirational (ASP) cropping systems, improving capabilities for acquiring, storing, and providing data to the LTAR Network and the larger agricultural community (Objective 4).
Progress Report
The Long-Term Agroecosystem Research (LTAR) common experiment at the Kelley Farm drainage plots was continued in 2019 and 2020. Established treatments contrasted different Nitrogen (N) management strategies (Objective 1), and included measurements of nutrient losses (N, Phosphorus (P), Potassium (K), and Sulphur (S)) in tile drainage (Objective 2). The experiment compares a business as usual (BAU) corn-soybean (C-S) cropping system with tillage and fixed N fertilizer applications to three alternative C-S systems: 1) no-till C-S; 2) no-till C-S with a cereal rye winter cover crop; and 3) a system with a winter camelina crop following corn that is relay cropped with the subsequent soybean crop. Each of these alternative systems uses the late-spring nitrate test to determine spring sidedress N application rates. In 2019, camelina and soybean crops were harvested, and above-ground biomass and nutrient content measurements were made, as were nutrient contents for oilseed and grain. The nitrate-N loss in tile drainage for the camelina relay cropped with soybeans (12.3 kg N/ha) was marginally reduced compared with the conventional C-S (BAU) without a cover crop (13.6 kg N/ha), but was greater than the C-S system with a winter rye cover crop (4.2 kg N/ha). These results differ from our 2017 data, and we are conducting further analysis of data to investigate potential causal factors. Changes in nutrient pools in soil are evaluated by profile sampling in each plot. Similar efforts are ongoing for the 2020 growing season. Established treatments at the Organic Water Quality site contrasted a conventional corn-soybean agroecosystem with an organic corn-soybean-oat-alfalfa-alfalfa system and an organic forage production system (Objective 1), using replicated, tile-drained plots. In 2019, yield data were collected, but have yet to be summarized due to the retirement of the Co-PI. Similarly, data on nitrate-N loss in tile drainage from these systems (Objective 2) during 2019 are still being processed. The use of a flame cultivator greatly reduced the weed density (visual assessment) in the 2019 corn crop and 2020 soybean crop. Key soil health metrics (Objective 3), including wet aggregate stability, organic carbon content, pH, extractable P and K, and potentially mineralizable N also were measured at both sites. Current data (2018 and 2019) from the Kelley Farm drainage plots were deposited in an internal database at the National Laboratory for Agriculture and the Environment (NLAE). As available, these data are being exported to the NutriNet and LTAR databases (Objective 4).
Accomplishments
1. Meta-Analysis of tillage effects in biological indicators of soil health. ARS scientists in Ames, Iowa, and Columbia, Missouri, conducted a meta-analysis of published effects of chisel plowing (CP), no-tillage (NT), and perennial cropping systems (PER) relative to moldboard plow (MP) on seven soil health indicators: soil organic carbon (SOC), microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), soil respiration (Resp), active-carbon (AC), beta-glucosidase activity (BG) and soil protein (Prot) within four soil depth increments in 302 studies from throughout the U.S. Overall, converting from MP to CP primarily affected topsoil (0 to 15cm) SOC, MBC, and Resp, whereas converting from MP to NT significantly increased all seven soil health indicators in the topsoil. Below the topsoil, i.e., 15 to 25cm, NT had greater MBC, MBN, Resp, and BG relative to MP. Based on this meta-analysis, reducing tillage intensity, planting cover crops and/or minimizing crop residue removal within annual cropping systems can significantly improve soil biological health in the U.S. We also demonstrate that SOC and many other biological indicators are sensitive to management practices, confirming their utility in soil health assessment. Improving soil health builds the capacity of the soil to function as a vital, living ecosystem that sustains plants and animals.
Review Publications
Meehan, M.A., O'Brien, P.L. 2019. Using areal composition of riparian vegetation communities to identify thresholds in prairie streams. Rangeland Ecology and Management. 73(1):162-170. https://doi.org/10.1016/j.rama.2019.09.004.
O'Brien, P.L., Hatfield, J.L., Dold, C., Kistner-Thomas, E.J., Wacha, K.M. 2020. Cropping pattern changes diminish agroecosystem services in North and South Dakota, USA. Agronomy Journal. 112(1):1-24. https://doi.org/10.1002/agj2.20001.
Croat, S.J., O'Brien, P.L., Gasch, C.K., Casey, F.X., Desutter, T.M. 2020. Crop production on heavily disturbed soils following crude oil remediation. Agronomy Journal. 112:130-138. https://doi.org/10.1002/agj2.20077.
O'Brien, P.L., Hatfield, J.L. 2020. Extreme soil surface temperatures reflect need to rethink agronomic management. Agricultural & Environmental Letters. 5(1). https://doi.org/10.1002/ael2.20002.
Nunes, M.R., Karlen, D.L., Veum, K.S., Moorman, T.B., Cambardella, C. 2020. Biological soil health indicators respond to tillage intensity: A US meta-analysis. Geoderma. 369:114335. https://doi.org/10.1016/j.geoderma.2020.114335.
Rahutomo, S., Kovar, J.L., Thompson, M.L. 2018. Inorganic and organic phosphorus in sediments in the Walnut Creek Watershed of central Iowa, USA. Water, Air, and Soil Pollution. 229:72. https://doi.org/10.1007/s11270-018-3721-5.
Rahutomo, S., Kovar, J.L., Thompson, M.L. 2018. Phosphorus transformations in stream bank sediments in Iowa, USA, at varying redox potentials. Journal of Soils and Sediments. 19:1029-1039. https://doi.org/10.1007/s11368-018-2139-4.
