Location: Integrated Cropping Systems Research2013 Annual Report
1a. Objectives (from AD-416):
1. Determine the effects of tillage, corn residue removal, cover crop, and crop rotation on soil physical, chemical, and biological properties including greenhouse gas and soil carbon dynamics in conventional and organic agricultural production systems. Contribute to multi-location projects including Greenhouse gas Reduction through Agricultural Carbon Enhancement network (GRACEnet) and Renewable Energy Assessment Project (REAP). 2. Assess soil-landscape rehabilitation (movement of soil from areas of net accumulation to areas of net soil loss) as a means of improving soil characteristics, soil productivity, farm profitability, pesticide persistence and mobility, and soil erosion. 3. Develop crop rotation, soil nutrient cycling, corn residue removal and pest management practices that improve farming efficiency (increase unit output/unit input), and manage soils in a holistic approach to improve crop yield and quality while maintaining or reducing production inputs.
1b. Approach (from AD-416):
The need to produce ever-increasing amounts of food, feed, fiber, and biofuel feedstocks for a growing world population, increased production costs, and fluctuating commodity prices are difficult challenges faced by our customers. Additionally, potential global climate effects on the local environment, degradation of soil resources, and depletion of non-renewable resources (e.g., oil and phosphorus fertilizers) are important concerns of farmers in our region and throughout the U.S. To answer these challenges and concerns, we are conducting research to optimize soil, crop and pest management practices and to synthesize them into integrated production systems that are economically sound, environmentally sustainable, and provide maximized production efficiency. This interdisciplinary project aims to define, for the unique conditions of the northwest Corn Belt and northern Great Plains, the relationships between soil, crop, and pest management and the conservation of the soil resource. This work is essential for the development of integrated production systems and sustainable agriculture in this region. Transfer of these integrated production systems to our customers through fact sheets, management guides, field day presentations, and other mechanisms will lead to increased production efficiency, improved soil quality, rehabilitation of degraded soil resources, improved profitability, and reduced risk.
3. Progress Report:
Progress was made on all three objectives and their subobjectives. Within subobjective 1a, we completed analysis of soil fungal:bacterial (F:B) ratios using quantitative PCR on samples collected over multiple years from research to evaluate the impact of removing residue on soil health characteristics. This research is part of the cross-location ARS Resilient Economic Agricultural Practices (REAP) and national Sungrant projects. Soil samples were analyzed to evaluate the impact of removing residue on soil physical properties. Both of these results were integrated into a manuscript that reports the effects of corn stover removal on soil biological and physical properties at four ARS sites. Manuscripts are being prepared for a special journal issue to highlight research supported by Sungrant on cellulosic ethanol production systems. Row crop and forage crop rotation effects on yield, yield quality and soil condition continued for the 17th year. Samples were evaluated for inorganic carbon which is necessary to evaluate the impact on soil carbon storage deep in the soil profile. Within subobjective 1b: we concluded a seventh year of measuring greenhouse gas (GHG: CO2 + CH4 + N2O) fluxes on a biweekly basis in plots under alternative rotational management. We concluded a fifth year of measuring GHG fluxes on a biweekly basis in plots under differing corn residue removal levels. This project is part of the national ARS project Greenhouse gas Reduction through Agricultural Carbon Enhancement network (GRACEnet), and data has been entered into the central GRACEnet/REAP database. Research progress within objective 2, hypothesis 2a: Completed yield monitoring in areas of soil removal at the Minnesota site. Data collection is complete for soil properties, weed populations, and crop productivity; results are being analyzed. Soil carbon dynamics study is in progress; changes in soil carbon and other markers are being analyzed. Evaluation of herbicide persistence and mobility was completed. Objective 2, hypothesis 2b: Monitoring is progressing as planned. Progress completed within objective 3 consisted of field experiments to evaluate the impact of crop residue on corn establishment, growth, and yield. Experimental treatments included planting different corn densities (21,000 and 30,000 seed per acre) into multiple crop residues (cool and warm season crops). Additional field studies incorporated the presence of specific cover crops on their impact on the following crop. The following year corn emergence, in season growth and yield was collected. Results were summarized and publications are being prepared.
1. Diversified crop rotation decreases global warming potential. Information on soil carbon and soil gas exchange with the atmosphere is required to predict and prepare for future climate changes. To properly evaluate these parameters, data needs to be collected throughout the U.S. under regionally-specific agricultural management practices. The researchers at the ARS laboratory located in Brookings, SD are part of a national ARS effort to evaluate the impact of agricultural management practices on changes in soil carbon and greenhouse gas flux. Results from Brookings have found multiple benefits of corn grown in a diverse crop rotation (4 year) compared to the traditional 2 year rotation (corn/soybean). These benefits include lower fertilizer input, lower weed pressure, and lower pest pressure. There was no observed difference in surface soil gas flux with the different crop rotations. Soil carbon increased in the diversified rotation, but decreased in the traditional 2 year crop rotation. This change in soil carbon results illustrated that during the corn phase, the 2-yr rotation was a net producer of global warming potential while the 4-yr rotation was a net consumer of global warming potential. This research demonstrates that growing corn within a more diversified rotation can reduce global warming potential and could slow the rate of climate change.
2. Positive impact of crop diversity. Two of the most limiting factors impacting crop growth are water and nitrogen availability. Diversified crop rotations have the potential to increase nitrogen and water use efficiency and reduce the need for nitrogen fertilizer during the corn rotational phase. Research findings from a long-term experiment conducted by the ARS in Brookings, SD show that a five year rotation including two years of alfalfa increased corn yield by 54% compared to continuous corn, under the same nitrogen application rate. Additionally, this diversified five year rotation increased water use efficiency by 33% compared to continuous corn production. This research demonstrates that more diversified rotations can increase crop response to limited resources such as water and nitrogen when compared with a monoculture of corn.
3. Designing rotations to minimize sunflower impact on soil health. Sunflower is widely grown in the prairies of the United States and Central Asia. However, sunflower damages soil health because of its low after-harvest residue levels, thus affecting land productivity. Long-term rotation studies have shown that soil organic carbon and soil aggregate stability declines in rotations that include sunflower too frequently (once every 3 or 4 years). This decrease in soil health can have a negative impact on other crops grown in the rotation over time. Researchers at the ARS laboratory in Brookings, SD are evaluating longer crop rotation (5 or 6-years) under no-till soil management. Longer crop rotations that include high residue crop such as winter wheat or corn have led to an increase in soil health characteristics such as soil organic matter. These changes are enabling producers to grow sunflower without damaging soil health and land productivity.
4. Saflufenacil shows low retention and rapid dissipation in prairie soils. Saflufenacil is a new herbicide that can be used to control herbicide-resistant and other difficult weeds in corn, soybean, and other crops. To assess its expected effectiveness and behavior in the environment, ARS researchers in Brookings, SD led a series of laboratory studies to measure the retention and degradation of saflufenacil in soil. Results showed that saflufenacil interacts little with soils typical of the northern U.S. Corn Belt. Saflufenacil dissipated fairly quickly, with only half of the herbicide remaining two weeks after it was applied to surface soil. Based on these results, we expect that herbicide interactions with soil will not limit saflufenacil’s degradation or plant uptake in the root zone. Under typical conditions in the U.S. Corn Belt, saflufenacil is not likely to carryover and damage following crops, which is important for using this herbicide in rotational systems or those incorporating cover crops. Its low retention in soil could make saflufenacil prone to leaching shortly after application so, like all agricultural chemicals; it should be carefully used to avoid contaminating water supplies. Regulators, industry, and other scientists can use this information to evaluate saflufenacil’s potential for weed control, carryover, leaching, and runoff in a variety of soils in which it is likely to be used.
5. Soybean physiological response to aphid feeding injury. Understanding the physiological basis of soybean crop injury caused by aphid feeding is an essential step towards development of integrated pest and crop management practices that reduce yield loss to insects without using insecticides. ARS researchers at Brookings, South Dakota conducted a 2 year field study on the effects of soybean aphid feeding on plant growth and physiology. Aphid feeding injury reduced nitrogen-containing compounds in soybean plants. Aphid feeding had a greater negative impact on nitrogen that was fixed from the atmosphere than on nitrogen absorbed by roots from the soil. Thus, soil nitrogen fertilizer application could be an important management practice to reduce plant injury caused by the soybean aphid. Because soybean is a crop of major economic importance, development of pest management systems for this invasive pest is an important national priority.Anderson, R.L. 2013. Steps of yield advancement with no-till cropping systems in a semiarid climate. Grain. 74:103-109.