Location: Integrated Cropping Systems Research
2018 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. The additional year of field sampling and sample (soil and plant) analyses have been conducted on long-term field plots featuring different crop rotations. The objectives of these studies are to determine the effect of prior crop on the plant microbiome of soybean and corn and relate changes in the microbiome with plant performance. Analysis of Year 1 data has shown that fungi inhabiting the corn rhizosphere are more responsive to the prior crop than bacteria. Soybeans preceded by field pea had greater vigor than those preceded by corn. Soybean rhizosphere fungal communities with a winter wheat preceding crop were more diverse compared to corn as a preceding crop. Prospective biological measures of soil health (soil microbial biomass, soil extracellular enzyme activity, labile carbon, soil protein) were evaluated on four different four-year crop rotations compared to a two-year corn-soybean rotation. The crop rotational treatments have been in place for 16 years. We found that the inclusion of oat or sunflower into four-year crop rotations notably increased the responses of these soil health measures compared to the two-year corn-soybean rotation. The effect of prior crop was particularly noticeable compared to current crop. Soil samples collected in 2017 from select plots for measuring select soil health properties such as particulate organic matter, soil organic matter, and water stable aggregates, were analyzed and data analysis is underway. Fall soil samples will be collected following harvest of all crops to evaluate soil chemical properties and for developing fertilizer recommendations for the 2019 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 monitoring insect and disease pressures.
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 continued into the third year of field studies to examine the effect of cover cropping on soil moisture and temperature and their relationship with soil microbial activities. A suite of soil biological assays (soil microbial biomass, potentially-mineralizable N, soil extracellular enzyme activity, labile carbon, soil protein, and substrate-induced respiration) are being conducted in soils collected during the growing season. Preliminary data show differing responses with the interseeded cover crops depending on the current cash crop phase (corn or soybean). Soil moisture was continuously monitored at depths of 15, 30, 60, and 90 cm in plots with no cover crop and a cover crop mix. Seasonal changes in water storage were monitored in plots with no cover crop, a single species cover crop, and a mixed cover crop to estimate crop water use efficiency. Water samples were collected from 90 cm depth using porous suction cup lysimeters in plots with no cover crop and a cover crop mix to estimate leaching of nitrogen and phosphorus below the root zone. 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 2019 growing season.
We collaborated with a university partner to publish research results on 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 and REAPnet. 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 publishing 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. Diversification of crop rotations provides benefits by modifying soil microorganisms. The benefits of crop rotation have long been appreciated; however, the specific mechanisms that confer these benefits (increased soil fertility, enhanced pest and pathogen resistance) are not understood. ARS researchers at Brookings, South Dakota evaluated the effect of preceding crop (sunflower, pea, soybean, or corn) on subsequent growth of corn seedlings and the composition of microbial communities that inhabit their rhizosphere, a zone of elevated microbial diversity and activity associated with plant roots. Using soils from each of the four crops preceding corn in field plots, we raised corn seedlings in the greenhouse and evaluated their vigor and nutrient composition, and characterized the associated rhizosphere microbial communities. Corn seedlings grown in soils after sunflower and pea showed greater vigor compared to after soybean and corn. The relative abundance of arbuscular mycorrhizal fungi was significantly higher in soils from sunflower and corn treatments. Stressing the corn seedlings with western corn rootworm resulted in selection for specific microbial taxa. When corn seedlings were stressed by inoculation with Fusarium graminearum, root damage was significantly lower in soils from sunflower. In general, inoculation with F. graminearum affected known fungal endophytes including Trichoderma and Endogone. In comparison to the biological stressors, rotation sequence had a greater effect on rhizosphere microbial communities, with larger effects observed for fungi compared to bacteria. This research helps define mechanisms responsible for the positive impact of crop rotation on soil quality and crop yields, promoting the selection and adoption of favorable crop rotation sequences.
2. Corn residue particle size impacts soil properties. Crop residue removal may degrade soils and their productivity. However, soil properties may not respond linearly to increasing levels of crop residue removal, suggesting an additional influence on soil properties beyond residue quantity. Mechanical operations during harvesting of grain and/or residues can influence the size distribution of residues remaining on the soil surface. Crop residue size distribution may be an important factor in moderating carbon and nitrogen dynamics in systems where crop residue is mechanically harvested. ARS researchers at Brookings, South Dakota evaluated the potential for corn residue particle size to influence microbial respiration and to produce persistent changes in soil C and N dynamics. They concluded that crop residue management operations resulted in characteristic residue size distributions that moderate decomposition activities, possibly influencing soil properties including nutrient availability to the growing crop. Soil amended with small size residue particles had a greater soil microbial respiration, and a longer lasting effect on soil carbon levels and nitrogen, compared with larger residue particles. Consideration of residue particle size distributions will promote more accurate interpretation of studies examining the effects of harvesting operations on soil properties and enhance the predictive value of these studies. Results will be used to develop recommendations for sustainably removing crop residue that take into account the impact of mechanical operations on carbon and nitrogen dynamics in soil.
3. Cover crops to maintain soil health when crop residue is removed. Removing plant residue from soil has been shown to have an adverse effect on soil health; however, the addition of cover crops may help mitigate these impacts. This is important because crop residues, the parts of the plant not harvested as grain, are being removed from the soil as a biofuel feedstock and also as supplemental feed for livestock. Research was conducted to evaluate the effectiveness of 7 years of cover crops on soil properties in both corn and soybean rotational phases when corn residue was removed in a no-till system. ARS researchers at Brookings, South Dakota found that immediately following corn residue removal (9 month), there was a shift in soil aggregate size, with an increase in small soil aggregates and a reduction in stable, larger aggregates, lending the soil more susceptible to erosion by wind and water. Cover crops mitigated these changes in treatments from which nearly all corn residue was removed. Additionally, residue removal significantly decreased soil particulate organic matter, which promotes formation of soil organic matter that is stable in the long term. Residue removal decreased soil microbial enzyme activities, but cover crops restored activities when residue was removed. Researchers concluded that cover cropping continued over multiple years can partially mitigate negative effects of crop residue removal on soil health, thus limiting soil erosion and maintaining nutrient cycling activities in the vulnerable period following residue removal.
4. Root sampling method measures insect feeding underground. Corn rootworms, which are destructive insect pests, have a long history of overcoming management strategies used by farmers. Knowledge of the spatial effects of corn rootworm larval feeding injury on corn root systems is the next step toward continued development of robust management strategies for this devastating insect pest. ARS researchers at Brookings, South Dakota modified a monolith sampling technique to measure root distribution in the soil profile after corn rootworm larval feeding. Soil monoliths from control or infested field plots were grid sampled, roots were washed from soil, and root length density plotted on contour plots. Total root length per monolith (sum of root lengths across all grid samples) was reduced about 26% by larval feeding. The contour plots revealed dramatic feeding injury reductions in root length density in the portion of the root system closest to the plant stem. This research demonstrates use of monolith techniques to explain the relationship between root length and insect feeding; this work could be expanded to better understand the impact of root injury on crop growth, nutrient uptake, and crops’ ability to withstand stress due to any pest or pathogen.
Review Publications
Benitez Ponce, M.S., Osborne, S.L., Lehman, R.M. 2017. Previous crop and rotation history effects on corn health and associated microbiome. Scientific Reports. 7:15709. https://doi.org/10.1038/s41598-017-15955-9.
Wegner, B.R., Osborne, S.L., Lehman, R.M., Kumar, S. 2018. Seven-year impact of cover crops on soil health when corn residue is removed. BioEnergy Research. 11:1-9. https://doi.org/10.1007/s12155-017-9891-y.
Vahyala, I.E., Osborne, S.L., Schumacher, T.E., Riedell, W.E. 2018. Corn residue removal effects on hydraulically effective macropores. Communications in Soil Science and Plant Analysis. https://doi.org/10.1080/00103624.2018.1464187.
Riedell, W.E., Osborne, S.L., Dagel, K.J. 2017. Maize residue removal and cover crop effects on subsequent soybean crops. Agronomy Journal. 109:2762-2770. https://doi:10.2134/agronj2017.05.0245.
Lai, L., Hong, C., Kumar, S., Osborne, S.L., Lehman, R.M., Owens, V. 2017. Soil nitrogen dynamics in switchgrass seeded to a marginal cropland in South Dakota. Global Change Biology Bioenergy. 10:28-38. https://doi.org/10.1111/gcbb.12475.
Gamble, J.D., Feyereisen, G.W., Papiernik, S.K., Wente, C.D., Baker, J.M. 2018. Summer fertigation of dairy slurry reduces soil nitrate concentrations and subsurface drainage nitrate losses compared to fall injection. Frontiers in Sustainable Food Systems. https://doi.org/10.3389/fsufs.2018.00015.
Stetson, S.J., Lehman, R.M., Osborne, S.L. 2018. Corn residue particle size affects soil surface properties. Agricultural and Environmental Letters. 3:180004. https://doi.org/10.2134/ael2018.01.0004.
Riedell, W.E., Osborne, S.L. 2017. Monolith root sampling elucidates Western Corn Rootworm larval feeding injury in maize. Crop Science. 57:3170-3178. https://doi:10.2135/cropsci12017.04.0218.
