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Research Project: Soil and Crop Management for Enhanced Soil Health, Resilient Cropping Systems, and Sustainable Agriculture in the Northern Great Plains

Location: Integrated Cropping Systems Research

2020 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. Data analyses were completed for a two-year rhizosphere microbiome dataset with two timepoints for each year from our long-term field plots featuring different crop rotations. We found corn and soybean yields were lowest in the simple corn-soybean rotation compared to the same grown in four different four-year crop rotations. Preliminary findings suggest distinctive microbial populations are enriched in the two-year corn-soybean rotation compared to the higher yielding four-year rotations, perhaps accounting for the lower crop performance in the two-year rotation. A temporal (biweekly) series of beta-glucosidase activity measurements was conducted within the long-term crop rotation field study to evaluate the effect of sample timing in comparison to the effects of crop rotation, current crop, and previous crop. These measurements were performed on four crop rotations, all crop phases, from March into July. Surprisingly, extracellular beta-glucosidase activities were highest in the very early spring (end March) and then around planting (mid-May), and then generally declined through July. These activities were not correlated with temperature. The effects of crop rotation, previous crop, and current crop were more frequently significant during May, compared to other dates. We are analyzing five years of measurements from field plots to examine the effect of interseeded cover crops on soil moisture and temperature and their relationship with soil microbial activities. A suite of soil biological assays (soil microbial biomass, potentially-mineralizable nitrogen, soil extracellular enzyme activity, labile carbon, soil protein, and substrate-induced respiration) were made on soil samples collected at multiple timepoints each year. We have observed differing responses among soil health measures with the interseeded cover crops that are often dependent on the current cash crop phase (corn or soybean). Research to evaluate the impact of incorporating cover crops into standing corn and soybeans was continued to meet the research Objective 2. We continued into the fifth and final year of field studies to examine the effects of cover cropping on soil nutrients and their relationship with soil microbial activities. A suite of soil biological assays and soil nutrient analyses are being completed on soils collected during the 2019 growing season. Cash crop growth, yield and quality were measured for a fifth year. Soil samples will be collected following fall harvest to evaluate soil chemical properties. Due to the inability to find a reliable seed source for winter camelina the relay crop portion of this experiment was not continued.


Accomplishments
1. Stacking management practices ensures improvements in soil properties. 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 used two long-term cropping field studies to illustrate the responses of soil structure indices and microbial activity to additional soil-building management tactics. Both studies had a set of base management tactics that included no-till. In one study, crop rotational diversity was the additional tactic added to the base practice. In the second study, crop residue retention and cover cropping were the additional tactics stacked on the base practice. 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.

2. Soybean yield and root growth improves following small grain. Developing crop rotations to support sustainable agriculture depends on understanding how crop rotations affect above- and below-ground crop characteristics. Researchers at ARS, Brookings, South Dakota, focused on investigating crop rotation effects on shoot dry weight and root characteristics of cereal and grain legume crops at anthesis as well as on grain yield. A long-term crop rotation experiment compared four 4-year rotations (including combinations of corn, soybean, spring wheat, winter wheat, oat, field pea, and sunflower) to a 2-year corn-soybean rotation. Above- and below-ground crop characteristics were evaluated. Researchers found that rotations had no significant effects on shoot dry weight at crop flowering. Small grains had greater root length density than grain legumes. Crop rotation did not impact root length density of any crop except for soybean between 0-90 cm. Soybean grown in the 4-year rotation following winter wheat had significantly less root length density than soybean following corn in either the 2-year or 4-year rotation. Additionally, soybean yield was significantly greater following winter wheat than other rotations. We concluded that soybean grown following winter wheat produced greater crop yield with less below-ground root length, compared to soybean following corn in the crop rotation.

3. Assessing the vulnerability and risk of groundwater pollution. Groundwater resources in semiarid lands are currently threatened by contamination from agricultural pesticides. It is highly advantageous to prevent pollution because clean-up is often not feasible, but tools are needed to identify those scenarios that pose an elevated risk of groundwater pollution. Researchers at Brookings, South Dakota, in collaboration with scientists at the National Agricultural Technology Institute (INTA) in Argentina, coupled models that estimate groundwater pollution risk based on hydrogeological setting, climate, and pollutant characteristics to assess the groundwater vulnerability and leaching potential of herbicides that are commonly used in central Argentina. The resulting maps were compared against herbicide detections in the aquifers underlying the study area. We found that these modeling approaches are generally applicable to semiarid lands of central Argentina and perhaps more broadly. Scientists, those who formulate risk assessments, regulators, and land managers can use these results to formulate plans to prevent groundwater pollution by agrochemicals.


Review Publications
Lehman, R.M., Osborne, S.L., McGraw, K. 2019. Stacking agricultural management tactics to promote improvements in soil structure and microbial activities. Agronomy. 9(9): 539. https://doi:10.3390/agronomy9090539.
Bowles, T.M., Mooshammer, M., Socolar, Y., Calderon, F.J., Cavigelli, M.A., Culman, S.W., Deen, W., Drury, C.F., Garcia Y Garcia, A., Gaudin, A., Harkcom, W., Lehman, R.M., Osborne, S.L., Robertson, G., Salerno, J., Schmer, M.R., Strock, J., Grandy, A. 2020. Long-term evidence shows crop rotation diversification increases agricultural resilience to adverse climate conditions in North America. One Earth. 2:284-293.
Osborne, S.L., Chim, B., Riedell, W.E., Schumacher, T.E. 2020. Root length density of cereal and grain legume crops grown in diverse rotations. Crop Science. https://doi.org/10.1002/csc2.20164.
Montoya, J.C., Porfiri, C., Vazquez, P.M., Papiernik, S.K., Azcarate, P., Roberto, Z. 2020. DRASTIC and PIRI GIS-based indexes: Assessing the vulnerability and risk of groundwater pollution. In: Chantre, G. and González-Andújar, J. (eds) Decision Support Systems for Weed Management. Springer, Cham, Switzerland. https://doi.org/10.1007/978-3-030-44402-0_10.