Location: Agroecosystems Management Research
2023 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 involving 24 experimental plots at the Kelley Farm Drainage Plots (KFDP) located near Ames, Iowa, was continued in 2022 through 2023. Established treatments contrasted different nitrogen (N) management strategies in support of Objective 1, and included measurements of nutrient losses (N, phosphorus (P), potassium (K), and sulfur (S) in tile drainage in support of Objective 2. The experiment compared 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 (CC); 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 used the late-spring nitrate test to determine spring sidedress N application rates. In 2022, corn was harvested to quantify yield and nutrient contents in both the grain and above-ground biomass. Changes in nutrient pools in soil were also evaluated by profile sampling in each plot. In 2021, camelina and soybean crops were harvested, and above-ground biomass and nutrient content measurements were made, as were nutrient contents for oilseed and grain. Similar efforts are ongoing for the 2023 growing season with soybean as the planted crop.
The nitrate-N loss in tile drainage for the winter camelina aspirational corn system was marginally reduced compared with the conventional C-S (i.e., BAU) system without a CC, but it exhibited greater nitrate-N losses than the C-S system with a winter rye CC. These results are similar to the 2018 and 2020 data. Previously (2017 growing season), both winter rye and camelina were effective in reducing nitrate loss in drainage by 88 and 67%, respectively. During the 2019 growing season, 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 much greater than the C-S system with a winter rye cover crop (4.2 kg N/ha). Soybean yield after camelina was 3.39 Mg/ha and 3.89 Mg/ha after rye. However, camelina yield was 1.06 Mg/ha. Similar results were recorded in 2021, suggesting that the camelina relay cropping system must be adjusted to improve performance. Additionally, corn yields were slightly lower in all the aspirational treatments, suggesting a slight tradeoff when implementing conservation practices. The 2023 growing season will create additional data to evaluate these and the other systems. Each year, data from the KFDP have been deposited in an internal database at the National Laboratory for Agriculture and the Environment. As available, these data are being exported to the NutriNet and LTAR databases in support of Objective 4.
The KFDP were complemented with the Organic Water Quality research site measurements in support of Objectives 1-4. Established treatments at the Organic Water Quality research site located near Ames, Iowa, contrasted a conventional C-S agroecosystem, studied at the Kelley Farm, with an organic corn-soybean-oat-alfalfa-alfalfa system and an organic forage production system in support of Objective 1, using replicated, tile-drained plots. In 2022, yield data were collected, but have yet to be summarized due to the retirement of the ARS Co-PI. Similarly, data on nitrate-N loss in tile drainage from these systems during 2019-2022 are still being processed in support of Objective 2. Yield data were collected in each of the 2019 through 2022 growing seasons but have yet to be summarized. The use of a flame cultivator greatly reduced the weed density (visual assessment) beginning with the 2020 corn crop and 2021 soybean crop. Key soil health metrics in support of Objective 3, including wet aggregate stability, organic carbon content, pH, extractable P and K concentrations, and potentially mineralizable N were also measured.
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, which was about half the 2017 yields of 6.12 Mg/ha. Alfalfa yields were 2.47 Mg/ha, which was less than the 2017 yield of 4.26 Mg/ha, likely due to drought starting in mid-season. Nitrate-N 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, perhaps because 2017 was drier than previous years. Each year, data from the Organic Water Quality research site have been deposited in an internal database at National Laboratory for Agriculture and the Environment. When summarized, these data will be exported to the NutriNet and LTAR databases in support of Objective 4. A data management plan is in place to meet the agency goals in 2025 for data accessibility.
The research at the Long-Term Agroecosystem Research (LTAR) Common experiment at the KFDP and the Organic Water Quality research site near Ames, Iowa, will continue in FY2024. A new project investigates alternative combinations of crops and climate-smart management in systems that include cover crops and double cropping within a C-S system, Right source, Right rate, Right time, and Right place (4R) nitrogen (N) management, silvopasture, and organic production with extended crop rotations. Specifically, we will investigate the development of climate-smart frameworks for providing actionable information on both conventional and aspirational C-S cropping systems, including organic systems, with foci on nutrient cycling, soil water dynamics, indicators of soil health, and other ecosystem services. This complementary project also examines how diversified systemwide management affects water- and light-use efficiency of row crops and pastures. The approaches we have used in C-S systems will be applied to pasture systems to provide quantitative assessments of the value of silvopasture systems in the Midwest. The project will also develop actionable data on the influence of microclimates modified by conservation management practices (such as no-till, relay or double cropping, extended rotations) on production efficiency and resilience of C-S, organic, agroforestry, and forage-based cropping systems.
Accomplishments
1. Use of winter camelina as a cover crop shows mixed results on nitrogen losses. Use of a winter-hardy oilseed crop within the common corn-soybean rotation in the upper Midwest has potential to increase farmer revenue while providing the environmental benefits of a cover crop. ARS scientists at the Upper Mississippi River Basin Long-Term Agroecosystem Research (LTAR) Network site in Ames, Iowa, compared the agronomic and environmental performance of a corn-soybean rotation with a corn-winter camelina-soybean relay cropping system by evaluating crop yield, nitrate losses in subsurface drainage and nitrous oxide emissions. Winter camelina yields were relatively low, but the sum of soybean and camelina yields in the system led to the highest production of any treatment during the soybean phase. Although included as a winter cover, the camelina system did not reduce nitrate leaching compared with the corn-soybean rotation. Management changes to accommodate the winter camelina crop increased nitrous oxide emissions three-fold in the camelina-soybean phase of the relay cropping system. Most of the increase was tied to fall nitrogen fertilizer application to the camelina. Later spring sidedress nitrogen applications resulted in only minor increases in nitrous oxide emissions. This study provides new insights and tools for optimizing the winter camelina relay cropping system and reducing nitrogen losses to the environment. The study suggests it may be necessary to combine multiple conservation practices to reduce environmental impacts in these systems. This information is important for scientists and crop advisors who want to know the best cover crops to use in the upper Midwest.
2. Double cropping winter rye cover crop with soybean simultaneously increases producers’ production while reducing nitrogen losses. Simultaneous goals for increasing crop production and cellulosic bioenergy production while reducing the environmental impacts of agriculture put multiple pressures on growers and conservation programs to develop and implement sustainable intensification strategies. Double-cropping winter rye cover crops with soybean in the North Central U.S. could help with the global effort to sustainably intensify agriculture and increase cellulosic energy production, but studies addressing the management of these systems and quantifying the large-scale impacts are limited to non-existent. ARS scientists in Ames, Iowa, and St. Paul, Minnesota, and scientists with Iowa State University, Pennsylvania State University, and McGill University completed a field and modeling study that demonstrated harvesting fertilized rye cover crop biomass before planting soybean is a promising practice for the North Central U.S. to cost effectively maximize total crop production and net energy production while reducing N loss to drainage and the Mississippi River. This research will help in the efforts to design and implement effective management systems to reduce N loads to the Mississippi River Basin and Gulf of Mexico while increasing cellulosic bioenergy production.
Review Publications
Luiz Correia, B., Kovar, J.L., Thompson, M.L., Pavinato, P.S., Ferracciú Alleoni, L.R. 2023. Sugarcane green harvest management influencing soil phosphorus fractions. Soil & Tillage Research. 231. Article 105713. https://doi.org/10.1016/j.still.2023.105713.
Volf, M.R., Crusciol, C.A., Kovar, J.L., Rosolem, C.A. 2023. Unraveling the role of ruzigrass in soil K cycling in tropical cropping systems. Nutrient Cycling in Agroecosystems. 126:181-194. https://doi.org/10.1007/s10705-023-10283-z.
Malone, R.W., Radke, A.G., Herbstritt, S., Wu, H., Qi, Z., Emmett, B.D., Helmers, M., Schulte, L., Feyereisen, G.W., O'Brien, P.L., Kovar, J.L., Rogovska, N.P., Kladivko, E.J., Thorp, K.R., Kaspar, T., Jaynes, D.B., Karlen, D., Richard, T. 2023. Harvested winter rye energy cover crop: multiple benefits for North Central US. Environmental Research Letters. 18(7). https://doi.org/10.1088/1748-9326/acd708.
Phillips, C.L., Tekeste, M., Ebrahimi, E., Logsdon, S.D., Malone, R.W., O'Brien, P.L., Emmett, B.D., Karlen, D.L. 2023. Thirteen-year stover harvest and tillage effects on soil compaction in Iowa. Agrosystems, Geosciences & Environment. 6(2). Article e20361. https://doi.org/10.1002/agg2.20361.
Emmett, B.D., O'Brien, P.L., Malone, R.W., Rogovska, N.P., Kovar, J.L., Kohler, K., Kaspar, T.C., Moorman, T.B., Jaynes, D.B., Parkin, T.B. 2022. Nitrate losses in subsurface drainage and nitrous oxide emissions from a winter camelina relay cropping system reveal challenges to sustainable intensification. Agriculture, Ecosystems and Environment. 339. Article 108136. https://doi.org/10.1016/j.agee.2022.108136.
Malone, R.W., O'Brien, P.L., Herbstritt, S., Emmett, B.D., Karlen, D.L., Kaspar, T.C., Kohler, K., Radke, A.G., Lence, S.H., Wu, H., Richard, T.L. 2022. Rye-soybean double-crop: planting method and N fertilization effects in the North Central US. Renewable Agriculture and Food Systems. 37(5):445-456. https://doi.org/10.1017/S1742170522000096.
Herbstritt, S., Richard, T.L., Lence, S.H., Wu, H., O'Brien, P.L., Emmett, B.D., Kaspar, T.C., Karlen, D.L., Kohler, K., Malone, R.W. 2022. Rye as an energy cover crop: Management, forage quality, and revenue opportunities for feed and bioenergy. Agriculture. 12(10). Article 12101691. https://doi.org/10.3390/agriculture12101691.
Logsdon, S.D., O'Brien, P.L. 2022. Runoff and nutrient losses in extended and conventional crop rotations. Agrosystems, Geosciences & Environment. 5(4). Article 20318. https://doi.org/10.1002/agg2.20318.
