Location: Agroecosystems Management Research
2019 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
Established treatments at the Kelley Drainage Plots contrasted different nitrogen management strategies (Objective 1), including measurements of nutrient losses (nitrate, phosphorus, potassium, and sulfur) in tile drainage from replicated plots (Objective 2). Key nitrogen management strategies included reduced tillage and no-till, coupled with spring nitrogen fertilizer application rates determined via soil testing and the use of rye cover crops or winter camelina. The control agroecosystem consisted of a fixed nitrogen fertilizer rate with spring tillage and without a cover crop. The main crops in all systems are corn and soybeans. Nutrients in drainage water, plant biomass accumulation and nutrient content, and key soil health metrics (Objective 3) were measured. Soil health measures include wet aggregate stability, organic carbon content, pH, extractable phosphorus and potassium, and potentially mineralizable nitrogen. Current and historical data (2002 to 2018) at this site were deposited in an internal database at the National Laboratory for Agriculture and the Environment (NLAE). This database will be able to export data to the NutriNet and Long Term Agroecosystem Research (LTAR) databases (Objective 4), as needed. Previously (2017 growing season), both winter rye and camelina were effective in reducing nitrate loss in drainage by 88% and 67%, respectively. Soybean yield after camelina was 3.39 Mg/ha and 3.89 Mg/ha after rye. However, camelina yield was 1.06 Mg/ha. The 2019 growing season will create additional data to evaluate these and the other systems. The winter camelina and rye cover crop treatments are aspirational/sustainable treatments within the LTAR Common Experiment. 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 the 2018 growing season, conventional corn yields were greater, at 15.40 Mg/ha, than organic yields, which averaged 11.50 Mg/ha. Soybean yields were equivalent between conventional and organic rotations, at 2.62 Mg/ha. Oat yields averaged 3.03 Mg/ha, very reduced from 2017 yields of 6.12 Mg/ha, and alfalfa yields were 2.47 Mg/ha, less than the 2017 yield of 4.26 Mg/ha, a reduced yield due to drought starting in mid-season. Nitrate loss data from these systems (Objective 2) during 2018 are still being processed. Nitrate losses in drainage water in 2017 were similar between the conventional and organic cropping systems, which differed from the pattern seen in 2013 through 2016, but 2017 was drier than previous years.
Accomplishments
1. Seed fungicides benefit corn seedling growth following a cereal rye cover crop. Cereal rye is the most commonly planted winter cover crop in Iowa. Corn yields are sometimes adversely affected following rye, and seedling fungal diseases are implicated in this reduction. ARS scientists in Ames, Iowa, and university collaborators investigated the potential use of seed fungicide to control pathogen infection of corn seedlings following a winter rye cover crop. Corn seedling disease from Pythium and Fusarium, two common fungal pathogens in soil, were greater following rye than no rye. Seed fungicides active against Pythium reduced disease and seedling growth, confirming our earlier observations of Pythium being transferred from the rye to the corn. Although Fusarium colonized rye roots, the seed fungicides targeting Fusarium were less effective, and corn seedling growth was less affected. The study suggests growers who use rye cover crops should benefit from the use of seed fungicides targeting Pythium. Avoiding corn seedling disease will improve corn yields and may increase adoption of cover crops.
Review Publications
Acharya, J., Bakker, M.G., Moorman, T.B., Kaspar, T.C., Lenssen, A.W., Robertson, A.E. 2018. Effects of fungicide seed treatments and a winter cereal rye cover crop in no till on the seedling disease complex in corn. Canadian Journal of Plant Pathology. 40(4):481-497. https://doi.org/10.1080/07060661.2018.1506503.
Kovar, J.L., Cantarella, H. 2019. Measuring crop available phosphorus. Better Crops. Available: http://www.ipni.net/publication/bettercrops.nsf/0/4C2F131ED7125B5F852583B7004F2DBC/$FILE/BC-2019-1%20p13.pdf.
Rahutomo, S., Kovar, J.L., Thompson, M.L. 2018. Varying redox potential affects P release from stream bank sediments. PLoS One. 13(12). https://doi.org/10.1371/journal.pone.0209208.
Rahutomo, S., Kovar, J.L., Thompson, M.L. 2019. Malachite green method for determining Phosphorus concentration in diverse matrices. Communications in Soil Science and Plant Analysis. https://doi.org/10.1080/00103624.2019.1635140.
Obrycki, J.F., Karlen, D.L., Cambardella, C.A., Kovar, J.L., Birrell, S.J. 2018. Corn stover harvest, tillage, and cover crop effects on soil health indicators. Soil Science Society of America Journal. 82(4):910-918. https://doi.org/10.2136/sssaj2017.12.0415.
Li, X., McCarty, G.W., Karlen, D.L., Cambardella, C.A., Effland, W. 2017. Soil organic carbon and isotope composition response to topography and erosion in Iowa. Journal of Geophysical Research-Biogeosciences. 10(10):1657. https://doi.org/10.1029/2018JG004824.
