Location: Soil Management Research2012 Annual Report
1a. Objectives (from AD-416):
1. Determine crop residue needs to protect soil resources and identify management strategies that enable sustainable production of food, feed, and biofuel. 2. Develop options for managing crop systems to reduce GHG emissions and increase C storage. 3. Assess bulk movement of soil within fields as a means of improving soil characteristics, soil productivity, farm profitability, pesticide persistence and mobility, and soil erosion. 4. Evaluate impacts of environmental changes (water, CO2, temperature) on traditional, biofuel and alternative crops to develop a model-based risk assessment of crop production under the most likely medium-term (10-30 yr) climate change scenario for the upper Midwest.
1b. Approach (from AD-416):
The project will generate information for balancing crop production goals with harvest of biomass for biofuel; develop management options to decrease greenhouse gas emissions and increase C storage in soil; evaluate an approach to remediate eroded soils; and provide information on crop response to climate change. Plot and on-farm approaches will be used to assess changes in soil carbon, greenhouse gas emission, soil quality indicators and production as a consequence of crop biomass harvest. This information will be identified locally and contribute to the national GRACEnet database on greenhouse gas emission and carbon storage. It will also contribute to national recommendations and guidelines through the REAP project. A farm-scale evaluation of field-scale soil movement (conducted to decrease soil spatial variability) will be used to develop improved management practices that restore productivity to eroded soils. This information will improve predictions of water and agrochemical transport in eroded soils, the response of soil biological communities to soil disturbance, and the short-term impact of soil erosion on soil C dynamics and soil productivity. This project will identify physiological and biochemical markers to develop or select cultivars adapted to climate change to develop environmentally- and economically-sustainable and diversified cropping systems that reduce risk and increase the probability of profitable crop production.
3. Progress Report:
To meet the expanding demands for food, feed and fuel, strategies are needed to simultaneously preserve productivity, protect the natural resources, mitigate greenhouse gas emission, and provide resilience to impact climate change. Substantial progress has been made toward developing soil and crop management systems that sustain agricultural production, readily adapt to climate change, minimize greenhouse gas emission, sequester carbon, and safeguard soil productivity while protecting environmental quality in the upper Midwest. Related to objective one, soil (erosion, soil C and microbial indicators) and crop response to stover harvest treatments in three separate fields was concluded and is being reviewed. This work found erosion indicators were more sensitive to stover harvest than other soil or crop parameters. Short-term resilience does not imply that long-term aggressive stover harvest is advisable; rather, it reinforces the need for continued empirical and modeling efforts to build a sustainable bioenergy industry. Integration of modeled and empirical data predicted that tilling with a moldboard plow or a chisel plow, even with returning all crop residues to the field, was not enough to maintain soil organic matter. Data analysis of feedstock quality and quantity of perennial grasses harvested in fall or spring harvest is in progress. The greenhouse gas emission measurements of objective two have been completed and are being summarized and statistically analyzed. Greenhouse gas data has been provided to collaborators for model validation and utilization. This data is being integrated with comparable datasets generated by the Renewable Energy Assessment network assessing direct impacts of stover removal on nitrous oxide emission. Three studies were completed which were designed to evaluate impacts of global environmental changes on traditional, biofuel and alternative crops to develop a model-based risk assessment of crop production under the most likely medium-term (10-30 yr) climate change scenario for the upper Midwest. First, a combined field and plot study included several crops with contrasting physiological attributes and seed composition comparing their ability to withstand abiotic stress (e.g., inadequate water). Dry matter partitioning among vegetative and reproductive plant parts and the concentration of carbohydrates, oil, protein and mineral nutrient in the seed was compared. Second, a plot-scale study was completed that assessed dry matter partitioning and mineral nutrient concentration (e.g., nitrogen, phosphorus, iron and others) at several growth stages. All data has been compiled into a database; statistical analyses are pending. Third, a growth chamber experiment compared the interaction of ambient and elevated carbon dioxide levels and non-limiting and limiting watering regimes and temperature stress on chickpeas, safflower, soybean and wheat. Biomass, dry matter partitioning and mineral nutrient concentration was determined on harvested material. Carbohydrate analysis on numerous samples is pending the replacement of a high pressure liquid chromatographer (HPLC).
1. Mitigating global warming with agricultural management practices. Agricultural management practices that reduce greenhouse gas emission (nitrous oxide and methane) and promote crop productivity are needed to mitigate global warming without sacrificing food production as society prepares to feed nine billion people. ARS researchers at Morris, MN, and Mandan, ND, found that comparable organic and conventional systems had similar nitrous oxide and methane emission. However, yield-scaled emission-scaled nitrous oxide and methane emission (carbon dioxide equivalents per unit yield) was 1.6- to 5-times greater in the organically-managed system, which had lower crop yield but similar emission compared to the conventionally-managed system. Thus, viability of organic systems to mitigate greenhouse gas emission may be compromised when crop productivity is reduced. Study results highlight the importance of assessing greenhouse gas emission and crop yield when developing agricultural systems that reduce global warming risks without sacrificing productivity or profitability.
2. Using basic plant biology to improve yield of cuphea, an emerging oilseed crop. Cuphea is a semi-domesticated potential oilseed crop characterized by indeterminate growth in which vegetative and reproductive growth stages overlap. Therefore, a considerable portion of a plant's resources, which were allocated to flowers, capsules and seed, is lost prior to harvest. Understanding how this plant partitions this dry matter is important for optimizing crop management to maximum oilseed yield. The biomass, nutrient allocation patterns and interrelationships, and their effects on seed yield of Cuphea were investigated under field and controlled conditions at the ARS Research Lab, Morris, MN. We found that changes in plant biomass and the transition from vegetative to reproductive stage are accompanied by changes in carbon, nitrogen and phosphorus contents and their ratios in root and stem, leaves and reproductive (flowers, capsules and seed) tissues. We concluded that the nitrogen to phosphorus ratios found in reproductive tissues and leaves are important in determining reproductive allocation in Cuphea. Yield increases of this emerging oilseed crop maybe possible if the nitrogen to phosphorus ratio can be manipulated during the transition to reproductive phase.
Johnson, J.M., Archer, D.W., Weyers, S.L., Barbour, N.W. 2011. Do mitigation strategies reduce global warming potential in the northern U.S. Corn Belt? Journal of Environmental Quality. 40:1551-1559.