Location: Integrated Cropping Systems Research
2021 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
This is the final report for the project. Our research found significant results impacting local, regional, and national stakeholders. Research results have been transferred in the form of 28 peer-reviewed research manuscripts, presentations to multiple audiences including local field days, regional and national meetings, and international research conferences. At least one scientist position was vacant for most of this reporting period.
Research was conducted under two objectives within the project. The first research objective was to 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 and the second objective was to integrate soil and crop management practices for more sustainable agricultural systems. Specific research accomplishments throughout the life of the project are highlighted below.
Our research demonstrated that diversification of crop rotations provided 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. Our research helped 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. Additionally, we found increasing crop rotational diversity had positive effects on corn and soybean plant vigor and grain yields, and these benefits could be linked to changes in the soil-plant microbiomes. In some cases, crop sequencing had an additional influence on the performance of the succeeding crop. Combining our results, we found a two-year, corn-soybean crop rotation perpetuated soil plant microbiomes that contained more potential plant pathogens and produced lower yields compared to four-year crop rotations. Crop production tactics including crop rotation can be used to modify plant-soil microbiomes to produce favorable outcomes in terms of crop performance.
Arbuscular mycorrhizal (AM) fungi are a key group of soil organisms known to influence soil health and ecosystem services. We found that the numbers of AM fungi propagules capable of colonization of plant roots was an effective measure of AM fungal response to agricultural management. Biomass measured by the neutral lipid fraction AM fungi biomarker (C16:1cis11) was also responsive, while the same biomarker in the polar lipid fraction was not as useful. Corn root colonization did not respond to treatment. However, high levels of corn root colonization by AM fungi were negatively related to corn yield and nutrient uptake. Understanding the range of responses in measures of AM fungi and their relationships with crop performance will advance identification and characterization of improved cropping practices. Improved cropping practices will reduce input costs, protect air and water quality, and preserve soils that are the foundation for food security.
Cover crops are among the practices purported to benefit soil quality. Addition of cover crops may help mitigate adverse effects of removing plant residue from soil for use as a biofuel feedstock or as supplemental feed for livestock. We 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.
Diversifying crop rotations is often observed to produce benefits to soil health, but they must be economically viable to be implemented. Research found 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. We found that the total cost for a two-year corn-soybean rotation was up to 14% greater compared to four-year rotations that also included corn and soybean. Corn yields for the two-year rotation were similar to the four-year rotation, while soybean yields were the lowest in the two-year rotation. Additionally, when nitrogen fertilizer application rate was lower than that recommended for maximum yield, the two-year rotation lacked resiliency as indicated by a decline in gross revenue and net revenue. In contrast, the four-year rotation that included pea was more resilient to less nitrogen fertilizer application. Among all the studied crop rotations, the corn/soybean/spring wheat/pea rotation had the highest net revenue, surpassing the two-year rotation by $36.42 per hectare. Our results suggest that extending the traditional two-year rotation to the more diversified four-year including pea could be an economically feasible practice in South Dakota that simultaneously reduces input cost and increases system resiliency. We found that by increasing crop diversification we could reduce nitrogen loss, increase soil carbon and crop yields, demonstrating that crop production systems can be adjusted to achieve higher yields and retain more nutrients and carbon in soil compared to existing practices.
Linking specific agricultural management tactics to quantifiable changes in soil health-related properties is a key objective for increasing adoption of the most favorable management practices. We found that observable effects of management tactics on soil properties were often dependent on the current crop phase sampled, even though the treatments were well-established. In some cases, a single additional management tactic produced a response, two tactics each produced a response, and sometimes there were interactions between tactics. But, importantly, we never observed a negative effect for any of the response variables when stacking soil health building practices in no-till cropping systems. The collective results from the two field studies illustrate that soil health improvements with stacking management tactics are not simply additive and are affected by temporal relationships inherent to the treatments. We conclude that the implementation of multiple positive management tactics increases the likelihood that improvements in soil properties can be documented with one or more of the proxy measures for soil health. This information is valuable to scientists researching related topics, to extension personnel advising producers, and to producers selecting management tactics.
Agricultural land that is severely degraded may need more extreme conservation measures to protect the soil resource and improve global food security. In collaborative research, we evaluated targeted replacement of topsoil to rehabilitate eroded land. In a severely eroded landscape, addition of 15 cm of soil increased crop biomass by 25 to 95% and increased grain yields by 20-49% (corn) and 12-59% (soybean), with the largest yield increases recorded in the most eroded landscape positions. The results of these studies indicate that soil-landscape rehabilitation may provide immediate and long-term benefits to soil productivity.
In a new research effort, this project was recognized and incorporated in the multi-location Grand Challenge Synergies project “Oat Renewal through Advanced Germplasm, Genomics, Phenomics, Disease Resistance, and Production Research,” resulting in the creation of a new Research Agronomist position at the location. The new scientist, who onboarded in February 2021, is evaluating oat germplasm in the field to help improve tolerance to drought, heat stress, and disease, and to improve oat yield and quality.
Accomplishments
1. Diverse crop rotations benefit plant performance by modifying soil microorganisms. Crop production systems may include annual rotation of different crops. Crop rotations frequently provide benefits in terms of increased crop yields, reduced input requirements, and resistance to pests and pathogens. However, the mechanisms producing these benefits from crop rotation are not well known. Soil microorganisms perform essential functions that enable crop production and are also influenced by crop rotation practices. In this study, ARS scientists in Brookings, South Dakota, evaluated changes in soil-plant microbiomes due to crop rotation and crop sequencing. We further correlated changes in these microbiomes to measures of corn and soybean crop performance within different crop rotations. We found increasing crop rotational diversity had positive effects on corn and soybean plant vigor and grain yields, and these benefits could be linked to changes in the soil-plant microbiomes. In some cases, crop sequencing had an additional influence on the performance of the succeeding crop. Combining our results, we found a two-year, corn-soybean crop rotation perpetuated soil-plant microbiomes that contained more potential plant pathogens and produced lower yields compared to four-year crop rotations. Crop production tactics including crop rotation can be used to modify plant-soil microbiomes to produce favorable outcomes in terms of crop performance.
2. Topsoil replacement can rehabilitate severely eroded soils. Conservation measures are critically needed to protect the soil resource and improve global food security. ARS scientists in Brookings, South Dakota, in collaboration with others, evaluated targeted replacement of topsoil to rehabilitate eroded land. Approximately 15 cm of topsoil were moved from lower landscape positions (where soil accumulates during erosion) to the upper slope (where erosion removes soil). Plant response was measured in the years that followed soil movement at sites in Minnesota and South Dakota; these experiments were conducted under relatively droughty conditions. Soil-landscape rehabilitation improved grain yields in a severely eroded landscape, but not a moderately eroded one. In the severely eroded landscape, addition of 15 cm of soil increased crop biomass by 25 to 95% and increased grain yields by 20-49% (corn) and 12-59% (soybean), with the largest yield increases recorded in the most eroded landscape positions. Soil addition also increased corn grain protein and test weight. No significant differences were observed in crop emergence rate or stand establishment. In the moderately eroded landscape, soil addition significantly increased soybean and wheat biomass, but not grain yield. During this study, areas of soil removal produced lower yields than areas from which no soil was removed. Results from areas of soil removal may be partially an artifact of the plot design, and more research is needed to evaluate approaches to prevent a decline in productivity in areas of soil removal. The results of these studies indicate that soil-landscape rehabilitation may provide immediate and long-term benefits to soil productivity. Growers, land managers, and conservation planners can use these results to include soil-landscape rehabilitation as a valuable part of an overall conservation plan to preserve and restore productivity to severely eroded soils.
3. Crop diversity to improve profitability and yield resilience. Crop yield and economic profitability are both highly dependent on local crop management, soil characteristics, and weather conditions, and are among the most influential factors when producers are choosing a cropping system. In this study, ARS scientists in Brookings, South Dakota, compared the economic returns of three different four-year diverse crop rotations with that of a two-year traditional crop rotation in eastern South Dakota. The rotations included were corn/soybean/spring wheat/pea, corn/pea/winter wheat/soybean, corn/oat/winter wheat/soybean, and corn/soybean. We found that total cost for the two-year rotation was up to 14% greater compared to the four-year rotations. Corn yields for the two-year rotation were similar to the four-year rotation, while soybean yields were the lowest in the two-year rotation. Additionally, when nitrogen fertilizer application rate was lower than that recommended for maximum yield, the two-year rotation lacked resiliency as indicated by a decline in gross revenue and net revenue. In contrast, the four-year rotation that included pea was more resilient to less nitrogen fertilizer application. Among all the studied crop rotations, the corn/soybean/spring wheat/pea rotation had the highest net revenue, surpassing the two-year by $36.42 per hectare. Our results suggest that extending the traditional two-year rotation to the more diversified four-year including pea could be an economically feasible practice in South Dakota that simultaneously reduces input cost and increases system resiliency.
Review Publications
Schneider, S.K., Cavers, C., Duke, S.E., Schumacher, J.A., Schumacher, T.E., Lobb, D.A. 2021. Crop responses to topsoil replacement within eroded landscapes. Agronomy Journal. 113:2938-2949. https://doi.org/10.1002/agj2.20635.
Graham, C., Ramos-Pezzotti, M., Lehman, R.M. 2021. Short-term impacts to the soil microbial population during grassland conversion to cropland. Soil & Tillage Research. 206. Article 104839. https://doi.org/10.1016/j.still.2020.104839.
Neupane, A., Bulbul, I., Wang, Z., Lehman, R.M., Nafziger, E., Marzano, S. 2021. Long term crop rotation effect on subsequent soybean yield explained by soil- and root-associated microbiome and soil health indicators. Scientific Reports. 11. Article 9200. https://doi.org/10.1038/s41598-021-88784-6.
Benitez, M., Ewing, P.M., Osborne, S.L., Lehman, R.M. 2021. Rhizosphere microbial communities explain positive effects of diverse crop rotations on maize and soybean performance. Soil Biology and Biochemistry. Article 108309. https://doi.org/10.1016/j.soilbio.2021.108309.
Feng, H., Wang, T., Osborne, S.L., Kumar, S. 2021. Yield and economic performance of crop rotation systems in South Dakota. Agrosystems, Geosciences & Environment. 4(3). Article e20196. https://doi.org/10.1002/agg2.20196.
