Location: Agroecosystems Management Research
2021 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) Croplands Common Experiment (CCE) at the Kelley Farm Drainage Plots located near Ames, Iowa, was continued in 2020 and 2021. Established treatments contrasted different Nitrogen (N) management strategies (Objective 1) and included measurements of nutrient losses (N, Phosphorus (P), Potassium (K), and Sulfur (S)) in tile drainage (Objective 2). This experimentation compares a business-as-usual (BAU) corn-soybean (C-S) cropping system using conventional tillage and fixed N fertilizer application to three alternative (aspirational) C-S systems: i) no-till C-S; ii) no-till C-S with a cereal rye winter cover crop (CC); and iii) corn followed by a winter camelina crop that is relay cropped with the subsequent soybean crop. Each of these alternative systems uses a late-spring nitrate test to determine sidedress N application rates for the corn crop. In 2020, corn was harvested to quantify yield and nutrient contents in both the grain and above-ground biomass. The nitrate-N loss in tile drainage for the aspirational corn and camelina relay cropped with soybean treatment was marginally reduced compared with the conventional C-S (i.e., BAU) without a CC, but was greater than the C-S system with a winter rye CC. These results are similar to the 2018 data. Changes in nutrient pools in soil were also evaluated by profile sampling in each plot. Similar efforts are ongoing for the 2021 growing season with soybean as the planted crop. Established treatments at the Organic Water Quality site contrasted a conventional C-S agroecosystem with an organic corn-soybean-oat-alfalfa-alfalfa system and an organic forage production system (Objective 1), using replicated, tile-drained plots. In 2020, 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 (Objective 2) during 2020 are still being processed. Data were not summarized due to the retirement of the ARS Co-PI as well. The use of a flame cultivator greatly reduced the weed density (visual assessment) in the 2020 corn crop and 2021 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 (2019 and 2020) from the Kelley Farm Drainage Plots were 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 (Objective 4).
Accomplishments
1. Early-season growth of corn in Iowa may benefit from sulfur (S) fertilizer. Erosion of high-fertility hill slope soils, fewer S impurities in fertilizers, and decreased atmospheric deposition of S throughout the upper Midwest suggest that S may become a more widespread limiting nutrient for corn production. An ARS scientist in Ames, Iowa, evaluated the efficacy of three different S fertilizers as S sources for corn grown in three diverse Iowa soils. The growth of young corn plants and the S captured by the plant roots generally increased when more S fertilizer was applied to the three soils, but the response was related to the type of soil. Plant uptake of S was not related to the type of S fertilizer applied. Results demonstrated that S fertilizer may be beneficial to corn growth, leading to increased production on some soils. The results of this research will benefit both commercial growers and the fertilizer industry by providing nutrient management guidelines that maximize crop S utilization and grain yields.
2. Relationship between plant-to-plant variability and crop yield exists in corn, but not soybean. ARS scientists in Ames, Iowa, evaluated plant-to-plant variability of corn and soybean development and yield over four years under three tillage management practices: no tillage, strip tillage, and chisel plow. Over the four-year study, the response of both corn and soybean to different tillage practices was inconsistent. In years receiving average precipitation, tillage had little effect on plant biomass or yield variability. In years with excessive early-season precipitation, tillage with a chisel plow led to more uniform plant stands with higher yields. Overall, lower plant-to-plant variability in corn stands typically led to higher yields, but plant-to-plant variability was not correlated with yield in soybean. Additionally, plant biomass variability in early phenological stages was not a good predictor of yield variability or overall yield. Thus, these findings suggest that management practices that encourage plant stand uniformity have the potential to increase yields in corn, but not soybean. However, the lack of relationship between early-season variability and overall crop yield indicates that growers should be cautious about implementing management based on variability in biomass accumulation during early growth stages.
Review Publications
O'Brien, P.L., Hatfield, J.L. 2021. Plant-to-plant biomass and yield variability in corn–soybean rotations under three tillage regimes. Agronomy Journal. 113(1):370-380. https://doi.org/10.1002/agj2.20514.
Meehan, M.A., O'Brien, P.L., Hecker, G.A., Printz, J.L. 2021. Integrating rangeland health and stream stability in assessments of rangeland watersheds. Rangeland Ecology and Management. 75:104-111. https://doi.org/10.1016/j.rama.2020.12.005.
Kral-O'Brien, K.C., O'Brien, P.L., Hovick, T.J., Harmon, J.P. 2021. Meta-analysis: Higher plant richness supports higher pollinator richness across many land use types. Annals of the Entomological Society of America. 114(2):267-275. https://doi.org/10.1093/aesa/saaa061.
Kovar, J.L. 2021. Maize response to sulfur fertilizer in three Iowa soils. Communications in Soil Science and Plant Analysis. 52(8):905-915. https://doi.org/10.1080/00103624.2020.1869773.
Wacha, K.M., Huang, C., O'Brien, P.L., Papanicolaou, T.N., Hatfield, J.L. 2021. Quantifying the time-specific kinetic energy of simulated rainfall using a dynamic rain gauge system. Agricultural & Environmental Letters. 6(1). Article e20042. https://doi.org/10.1002/ael2.20042.
O'Brien, P.L., Kral-O'Brien, K.C., Hatfield, J.L. 2021. Agronomic approach to understanding climate change and food security. Agronomy Journal. https://doi.org/10.1002/agj2.20693.
Wacha, K.M., Hatfield, J.L., O'Brien, P.L., Dold, C. 2021. Short-term effects of nitrogen source on soil properties and plant growth. Agrosystems, Geosciences & Environment. 4(2). Article e20176. https://doi.org/10.1002/agg2.20176.
