Location: Integrated Cropping Systems Research
2017 Annual Report
Objectives
Objective 1: Evaluate no-till production practices using diverse crop rotations and cover crops to manage soil in a holistic manner, improve farming efficiency (increase unit output/unit input) and sustain soil productivity.
Objective 2: Integrate soil and crop management practices for more sustainable agricultural systems applicable regionally and across a wide range of environmental conditions.
Approach
Healthy soil is fundamental to all plant and animal life, therefore, proper management of soil resources is essential. Recent concerns regarding global climate change as related to soil health and crop production are increasingly driving scientific research relevant to our customers. Producers in the northern Great Plains can utilize several management options that may improve soil health and ecosystem services including: no-till soil management, maintaining crop residues, diversifying crop rotations, and establishing cover crops. A region as variable as the northern Great Plains requires extensive research on how to best implement these and other beneficial management practices to improve sustainability.
To address these challenges, it is important to understand how soil and crop management practices directly and indirectly influence the soil-water-air environment. Our previous research identified management options that more efficiently utilize inputs (including water, nutrients, pesticides, labor, and fuel), showing that integration of multiple practices often produced more than additive benefits. In this project, we seek to integrate multiple management practices to result in resilient agricultural systems that are valid across a wide range of environmental conditions. We expect that this research will provide multiple systems services such as increased soil health, conservation of natural resources, improved crop yields and quality, and development of habitat for insects and wildlife, while maintaining or improving economic sustainability for producers.
Transfer of these integrated production systems to our customers through scientific publications, management guides, field day presentations, partnership with action agencies, and other mechanisms will lead to increased production efficiency, improved soil resource conservation, positive ecosystem services, and decreased environmental costs. The project seeks to (a) determine useful metrics for quantifying ecosystem services and environmental costs (particularly for soil biology and soil organic matter) and (b) quantify differences between systems to provide information about synergisms and trade-offs in the studied systems.
Progress Report
Research progress was made on all objectives and sub-objectives within the approved research project. Long-term research to evaluate the impact of crop diversity on crop yield, quality and soil properties was continued to meet research Objective 1. Specifically we conducted greenhouse (using field soils) and field experiments to determine the effect of prior crop on the plant microbiome of soybean and corn and related changes in the microbiome with plant performance. The completed greenhouse studies showed that the identity of the prior crop (corn, sunflower, pea, or spring wheat) had a much greater effect on corn rhizosphere microbial communities than infestation with the crop pest corn rootworm or the pathogen Fusarium graminearum. The effect of prior crop on corn rhizosphere microorganisms was much greater for fungal communities compared to bacterial communities. Corn and sunflower enriched the corn rhizosphere in arbuscular mycorrhizal fungi relative to pea and soybean. Field studies examining the effects of prior crop on corn and soybean rhizosphere microbes are in their second year with sampling and sample analyses proceeding. Soil samples were collected in the spring from select plots for measuring select soil health properties such as particulate organic matter, soil organic matter, and water stable aggregates, and fall soil samples will be collected following harvest of all crops to evaluate soil chemical properties and for developing fertilizer recommendations for the 2018 growing season. Measurements made during the reporting period included crop growth, canopy characteristics, root system quantification, crop mineral nutrient relationships, crop yield, seed composition, soil nutrients, nutrient leaching, and surveying insects and disease.
Research to evaluate the impact of incorporating cover crops into standing corn and soybeans was continued to meet the research Objective 2. We examined the effects of cover cropping on soil moisture and temperature and their relationship with soil microbial activities. We found that interseeded cover crops into soybean increased soil microbial biomass and potentially-available N. Other soil analyses are under way to measure soil biological activity as it relates to plant nutrient availability. We are measuring soil extracellular enzyme activity, labile carbon, soil protein, and substrate-induced respiration. We installed sensors in treatments 1 and 5 and monitored soil moisture continuously at depths of 15, 30, 60, and 90 cm. We monitored seasonal changes in water storage in treatments 1, 3, 5, and 7. We installed porous suction cup lysimeters in treatments 1 and 5 but a critical technician vacancy delayed the installation so that water samples were not collected for most of the 2017 growing season. Cash crop growth, yield and quality were measured for a third year. Soil samples will be collected following fall harvest to evaluate soil chemical properties and to make fertilizer recommendations for the 2018 growing season.
We collaborated with a university partner to measure greenhouse gas (GHG: CO2 + CH4 + N2O) fluxes on field plots with treatments of corn stover removal (0, 100%) and cover cropping (+, -). This research is part of the nationwide ARS networks and cross-location projects: GRACEnet (Greenhouse gas Reduction through Agricultural Carbon Enhancement network)and REAPnet (Renewable Energy Assessment Project). Data from prior years of greenhouse gas flux measurements were entered into the central GRACEnet/REAP database. We continued our collaboration with a university partner on measuring GHG fluxes from switchgrass plots receiving different levels of N fertility. This research is part of national Sungrant efforts in developing systems for cellulosic ethanol production.
Accomplishments
1. Reduce nitrogen loss, increase soil carbon and crop yields by crop diversification. Improving crop production practices will increase producer profit and minimize any negative off-farm impacts. Diversification of crop rotations is a fundamental tactic that can produce substantial producer and societal benefits. Using long-term research plots established in the northern Corn Belt, ARS researchers at Brookings, South Dakota evaluated a two-year conventional corn-soybean rotation in comparison to a four-year corn-field peas-winter wheat-corn rotation. Both cropping rotations were conducted under no-till conditions. Compared to the two-year rotation, the four-year rotation increased soybean yield by 22%, decreased by 24% the loss of nitrogen through atmospheric emissions of nitrous oxide, and increased the rate and depth of soil organic carbon accumulation. Results demonstrate that crop production systems can be adjusted to achieve higher yields and retain more nutrients and carbon in soil compared to existing practices. It is critical to have demonstrated solutions that apply to regionally-specific conditions and management practices so that producers can respond to market and policy influences. Improving the efficiency of cropping systems improves producer profitability, reduces soil loss and degradation, and supports public interests by improving water and air quality.
2. Arbuscular mycorrhizal fungi not inhibited by seed-applied fungicides. Fungicidal seed coatings have become standard on commodity crop seed to control pathogenic fungi prior to germination. However, seed-applied fungicidal formulations containing multiple systemic ingredients could impact non-target soil fungi such as obligate plant symbiotic arbuscular mycorrhizal (AM) fungi. Symbiotic AM fungi commonly supply nutrients (particularly phosphorus), water, and pest/pathogen resistance to their plant hosts. ARS researchers at Brookings, South Dakota evaluated the potential for contemporary, seed-applied fungicidal formulations to inhibit AM fungal root colonization or alter plant nutrient content of corn, soybean, and oat. Commercial fungicidal seed coatings applied at their labeled rate did not significantly reduce root colonization by AM fungi or phosphorus content of any plant compared to the untreated control. Plant genotype (hybrid or variety) significantly affected AM fungal root colonization and plant nutrient content for the crops studied. The potential for non-target effects of seed-applied fungicides has been an ongoing concern of producers who are interested in promoting soil biological diversity and function. These results indicate that other factors may be more important in determining the beneficial soil fungi population.
3. Crop diversity: a recipe for productive and sustainable agriculture. Highly specialized cash-grain production systems based upon corn-soybean rotations under tilled soil management are common in the northwestern U.S. Corn Belt. This rotation is expensive to maintain in terms of agricultural inputs needed such as pesticides and fertilizer cost. A long-term study, initiated in 1997 by ARS researchers at Brookings, South Dakota, was conducted to determine if diversification of this ubiquitous corn-soybean rotation would affect soil characteristics and crop productivity under no-till soil management. They determined the effects of a 2-year rotation (corn-soybean), 3-year rotation (corn-soybean-spring wheat), and 5-year rotation (corn-soybean-oat/pea hay-alfalfa-alfalfa) on soil bulk density, soil carbon sequestration, and residual soil nitrate-N as well as on corn and soybean yield productivity and seed protein. They found that diversification of the corn-soybean rotation with oat/pea and alfalfa hay made soils less dense, increased soil carbon, increased soil nitrogen available to corn and soybean phases, and increased corn and soybean grain yield as well as seed protein. In contrast, diversification with wheat only increased corn and soybean grain yield. Findings were communicated to producers, crop consultants and scientist through various outreach activities. These data elucidate the complex relationships between soil attributes, crop rotations, and crop yield that help provide a basis for improving the productivity and sustainability of agricultural systems to meet the demand for increased productivity while maintaining or improving the soil resource.
4. Fighting soil salinity in the northwest U.S. corn belt. Soil salinity is expanding in the east central Dakotas, and limiting crop productivity. Because of poor surface drainage and saline parent materials, soil water deposited during wet years moves up from deep in the soil profile during dry periods, where it evaporates and leaves behind high concentrations of salt. As salt concentrations build up, farmers can no longer use their land to plant salt-susceptible crops important to the economic sustainability of the region. In an effort to fight increasing salinity, ARS researchers at Brookings, South Dakota collaborated with soil health specialists at the USDA Natural Resources Conservation Service to investigate the use of perennial grasses to mitigate soil salinity. They found that cultivation of salt tolerant grasses reduced soil salinity and helped remediate the soil. Findings were communicated to producers, crop consultants and scientist through various outreach activities.
Review Publications
Riedell, W.E., Osborne, S.L. 2017. Row and forage crop rotation effects on maize mineral nutrition and yield. Canadian Journal of Plant Science. 97:645-653. https://doi.org/10.1139/cjps-2017-0006.
Cameron, J.C., Lehman, R.M., Sexton, P., Osborne, S.L., Taheri, W.I. 2017. Fungicidal seed coatings exert minor effects on arbuscular mycorrhizal fungi and plant nutrient content. Agronomy Journal. 109:1005-1012.
Lehman, R.M., Taheri, W.I. 2017. Soil phosphorus and reducing its loss from crop production systems using the activities of native soil microorganisms. Sustainable Agriculture Reviews. 22:15-36.
Lehman, R.M., Osborne, S.L. 2017. A diversified no-till crop rotation reduces nitrous oxide emissions, increases soybean yields, and promotes soil C accrual. Soil Science Society of America Journal. 81:76-83.
Riedell, W.E. 2016. Growth and ion accumulation responses of four grass species to salinity. Journal of Plant Nutrition. 39:2115-2125. doi: 10.1080/01904167.2016.1193611.
Mostafa, I., Hong, C., Singh, S., Kumar, S., Osborne, S.L. 2017. Swithchgrass biomass quality as affected by nitrogen rate, harvest time and storage. Agronomy Journal. 109:86-96.
Sandhu, S., Ussiri, D.A., Kumar, S., Chintala, R., Papiernik, S.K., Malo, D.D., Schumacher, T. 2017. Analyzing the impacts of three types of biochar on soil carbon fractions and physiochemical properties in a corn-soybean rotation. Chemosphere. 184:473-481. doi: 10.1016/j.chemosphere.2017.05.165.
