Location: Agroecosystems Management Research2015 Annual Report
Objective 1: Improve nutrient and water-use efficiency and decrease environmental impacts of corn-soybean systems in the Midwest. Sub-objectives: 1.1 Determine effects of cover crops, bio-char applications, and biomass removal for bio-energy feedstock production on soil nutrient dynamics and crop yield; 1.2 Determine winter cover crop and tillage effects on water quality and N balance in a corn-soybean rotation; 1.3 Determine winter cover crop effects on soil quality and plant health in a corn-soybean rotation; 1.4 Develop and populate a SQL structured database to link with crop simulation models to evaluate cropping system responses to changing climate and management practices. Objective 2: Evaluate nutrient cycling and environmental impacts of alternative cropping systems. Sub-objectives: 2.1 Determine effects of organic cropping systems on water quality and soil profile water storage; 2.2 Determine effects of organic cropping systems on soil C and N storage and soil quality; and 2.3 Develop and populate a SQL structured database to link with crop simulation models to evaluate alternative cropping system responses to changing climate and management practices. Objective 3: Intercompare crop and economic models and foster improvements in these models to increase their capability to utilize data from climate scenarios as part of AgMIP.
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 corn stover removal on nutrient cycling and the ability of winter cover crops to reduce nitrate losses and improve soil quality in a conventional corn-soybean production system. In an organic production system with extended rotations and manure application, we will examine system effects on nitrate losses and soil quality. To assess cultural practices that can improve nutrient- and water-use efficiency and decrease environmental impacts of corn-soybean systems in the Midwest, we will determine effects of cover crops, bio-char application, and biomass removal for bio-energy feedstock production on soil nitrogen (N), phosphorus (P), potassium (K), and sulfur (S) dynamics and corn yield, determine winter cover crop effects on N balance and water quality, determine cover crop effects on soil quality and plant health, and develop and populate a Structured Query Language (SQL) database to link with crop simulation models to evaluate cropping system responses to changing climate and management practices. To evaluate nutrient cycling and environmental impacts of alternative cropping systems, we will determine effects of organic cropping systems on water quality, soil profile water storage, soil carbon (C) and N storage, and soil quality. With the data, we will develop and populate a database to link with crop simulation models in order to evaluate alternative cropping system responses to changing climate and management practices.
With research addressing corn grown for grain and as a feedstock for the emerging bio-energy and bio-based products industries under a variety of management systems (Objective 1), we found that after the second growing season, potassium was again the most limiting nutrient for the growing crops. This suggests that fertilizer application rates, placement, and timing should be adjusted to meet the needs of different management scenarios, including continuous corn with a 30-inch row spacing, corn rotated with soybean, corn rotated with alfalfa, and a corn/cereal rye-soybean/winter wheat-tillage radish rotation in the current study. Differences in plant populations and tillage intensity, application of biochar, and use of cover crops did not affect corn grain or biomass yields during this second year of the study. In experiments examining the effect of cover crops on nitrate leaching in corn-soybean rotations (Objective 1), oat and winter rye cover crops substantially reduced nitrate concentration and load in tile drainage even after 12 years in this system. Other results showed that nitrate concentrations in drainage can be relatively high for these soils even when no nitrogen is applied. Additionally, nitrate concentrations were slightly higher for fall tilled treatments than for no-till treatments. In experiments examining corn seedling root diseases following cereal rye cover crops (Objective 1), we were able to show that seed fungicide treatments had more of an effect on infection of corn seedling mesocotyls rather than infection of the radicle and did not lessen infection rates of corn following a rye cover crop. Terminating a rye cover crop with glyphosate more than seven days before planting corn reduced the infection rate of corn seedling radicles. Additionally, the principal pathogens that increased on corn roots following a rye cover crop relative to the no cover crop treatment were from the Pythium genus. To evaluate alternative cropping systems (Objective 2), the USDA-ARS Organic Water Quality (OWQ) experiment, established in 2011, compares organic (corn, soybean, oat/alfalfa, alfalfa (C-S-O/A-A)) and conventional (corn, soybean (C-S)) crop rotations and an organic pasture (bromegrass, fescue, alfalfa, white clover) system. Thirty fully-instrumented, subsurface-drained plots (30.5 m x 30.5 m) laid out in a randomized block design with five field replications, isolate subsurface drainage from each plot and permit comparison of treatment effects on subsurface drainage water flow and nutrient concentrations. Temporal patterns of subsurface drainage water flux were similar for all cropping systems for all years, except for the pasture system in 2012, and subsurface drainage water nitrogen (N) concentrations were highest in the conventional C-S system except for the early spring 2012. Subsurface drainage water nitrogen loading loss for the entire three-year period from the conventional C-S system (79.2 kg N ha-1) was nearly twice as much as the nitrogen loss from the organic C-S-O/A-A system (39.9 kg N ha-1); the pasture system (16.5 kg N ha-1) lost the least amount of nitrogen over the three years. Results of this study suggest that organic farming practices, such as the application of composted animal manure and the use of forage legumes and green manures within extended cropping rotations, can improve water quality in Midwestern subsurface-drained landscapes.
1. Nitrate-N contamination of surface water is a major water quality concern in the upper Midwest USA. Environmental impacts associated with conventional agricultural production have encouraged producers to investigate alternative management practices, including organic farming methods. ARS scientists in Ames, Iowa, initiated a long-term study that compares tile drainage water nitrate-N losses for a conventional corn-soybean and an organic corn-soybean-oat/alfalfa-alfalfa organic grain cropping system. ARS scientists demonstrated that average annual nitrate-N concentrations were lower in tile drainage water collected from the organically managed rotation compared to the conventionally managed rotation. Total nitrogen loss for the conventional rotation (79.2 kg N/ha) was nearly twice as much as from the organic rotation (39.9 kg N/ha). These results suggest that organic farming practices can improve water quality in Midwestern tile-drained landscapes.
2. Database development for crop simulation models. ARS scientists in Ames, Iowa, assembled data representing three tillage systems (conventional tillage, strip tillage, and no-till) for a corn-soybean system to include weather, soils, and crop growth and yield data needed to evaluate corn and soybean simulation models as part of the Agriculture Model Intercomparison and Improvement Project (AgMIP). The AgMIP project is an international effort to intercompare crop simulation models and improve these models to be able to more accurately assess how crop production can be enhanced in the future. These efforts require data for validation and model improvement and one of the primary problems is the lack of consistency among crop models in the data requirements and format needed. The data assembled for the 2010 through 2014 growing seasons have been used to evaluate a new concept in data storage and retrieval by using standard nomenclature for the variables that allow for more rapid searching and assembly of the data for model calibration. Being able to more rapidly assemble these data and then link with crop models enhances our ability to evaluate different crop models and utilize these models to assess more effective management practices to enhance crop production to ensure a food secure world.
3. Bio-energy cropping systems utilizing corn stover require additional nutrient applications. Growing crops as a bio-energy feedstock has attracted the attention of many producers; especially in the Corn Belt states. The long-term effects of both increasing grain yields and removing stover on soil nutrient cycling, physical properties, and biological activity must be understood to ensure that corn yields meet both current and future demands. After six years of a field study conducted by ARS scientists in Ames, Iowa, comparing several corn biomass management systems with standard nitrogen, phosphorus, and potassium fertilizer management, we were able to show that concentrations of all nutrients in the growing crop could be maintained at optimum levels. During five of the six years the study has been conducted, differences in plant populations and tillage intensity, application of biochar, and use of cover crops did not affect corn grain or stover yields, demonstrating that long-term research is needed to evaluate and establish environmentally and economically sustainable management practices. The results of this research are providing nutrient management guidelines that maximize crop utilization and biomass yields, while preserving soil health, and will benefit commercial growers, as well as the fertilizer and emerging cellulosic ethanol industries.
Cambardella, C.A., Delate, K., Jaynes, D.B. 2015. Water quality in organic systems. Sustainable Agriculture Research. 4(3):60-69.
Delate, K., Cambardella, C.A., Turnbull, R. 2015. A review of long-term organic comparison trials in the U.S. Sustainable Agriculture Research. 4(3):5-14.
Ontl, T.A., Cambardella, C.A., Schulte, L.A., Kolka, R.K. 2015. Factors influencing soil aggregation and particulate organic matter responses to bioenergy crops across a topographic gradient. Geoderma. 255-256:1-11.
Gaston, L.A., Kovar, J.L. 2015. Phytoremediation of high phosphorus soil by annual ryegrass and common bermudagrass harvest. Communications in Soil Science and Plant Analysis. 46:736-752.
Basche, A.D., Miguez, F.E., Kaspar, T.C., Castellano, M.J. 2014. Do cover crops increase or decrease nitrous oxide emissions? A meta-analysis. Journal of Soil and Water Conservation. 69:471-482.
Myers, M.C., Mason, J.T., Hoksch, B.J., Cambardella, C.A., Pfrimmer, J.D. 2015. Birds and butterflies respond to soil-induced habitat heterogeneity in experimental plantings of tallgrass prairie species managed as agroenergy feedstocks in Iowa, USA. Journal of Applied Ecology. 52(5):1176-1187. doi: 10.1111/1365-2664.12503.
Moore, E.B., Kaspar, T.C., Wiedenhoeft, M.H., Cambardella, C.A. 2014. Rye cover crop effects on soil quality in no-till corn silage-soybean cropping systems. Soil Science Society of America Journal. 78(3):968-976. DOI: 10.2136/sssaj2013.09.0401.
Kladivko, E.J., Kaspar, T.C., Jaynes, D.B., Malone, R.W., Singer, J., Morin, X.K., Searchinger, T. 2014. Cover crops in the upper midwestern United States: Potential adoption and reduction of nitrate leaching in the Mississippi River Basin. Journal of Soil and Water Conservation. 69(4):279-291. DOI: 10.2489/jswc.69.4.279.