Corn Residue Removal Impacts on Soil, Water, and Air Resources for Biofuel Production

View the project final report

• 2010 annual report

Commodities

• Agronomic: corn

Practices

• Crop Production: conservation tillage, continuous cropping, no-till
• Education and Training: extension
• Energy: bioenergy and biofuels
• Natural Resources/Environment: carbon sequestration
• Production Systems: agroecosystems
• Soil Management: soil analysis, soil physics, soil quality/health

After two years of corn residue removal in poorly and well-drained soil sites, there were no significant decreases in grain yield. In general, removing residue increased grain yields due to soil warming under cold and wet conditions early in the spring. In addition, there were no significant decreases in total soil organic carbon (SOC) concentrations compared to baseline year. However, potential decreases in SOC sequestration were observed when residue was removed. The adoption of no-till and increased N rates did reduce some of the carbon (C) losses due to residue removal. However, only with adoption of no-till and nitrogen (N) rates greater than 150 lbs N per acre with very little residue removed, were there potential increases in soil C were observed. In the poorly drained soil site, approximately 15% of corn residue can be removed without seeing a net loss in potential SOC sequestration. In the well-drained site, only approximately 9% of the residue can be removed without having a net loss in potential SOC sequestration. Significant short term effects of residue removal on soil physical properties were observed. Increases of bulk density were observed with 100% residue removal regardless of tillage and increased N fertilization rate. Furthermore, decreases in soil aggregation were observed with residue removal, regardless of tillage and increased N fertilization rate. Subsequently, soil water infiltration rates were significantly reduced in the well-drained soil site. In general, the adoption of no-till over chisel plow and increased rates of N fertilization did offset some of the negative impacts of residue removal, but potential losses of SOC sequestration and deterioration of soil physical properties were still observed.

Introduction:

Crop residue left on the surface after harvest is a potential feedstock source for bioethanol production that may alleviate some of the United States dependence on foreign fuel and net greenhouse gas emissions (GHG). Although, it is currently more expensive to produce ethanol from lignocellulosics than from starches, it is projected that improvements in technology and scale of production will improve these costs. Additionally, the process of producing bioethanol from lignocellulosics is energetically positive; that is to say that the energy content of the ethanol is greater than the energy required to produce it. It is projected that lignocellulosic ethanol production will become a viable industry and could create an annual market for crop residue, increasing from approximately 195 million tons to 425 – 600 million tons.

The removal of crop residue, however, may require farmers to change their current tillage and fertilization practices to prevent against potential soil erosion. Crop residues play a significant role in improving soil physical and chemical properties that are essential in controlling wind and water erosion, which ultimately reduce sediment and other contaminant transport to water bodies and is critical for replenishing soil organic carbon (SOC). In addition, there is no currently published research on how various levels of crop residue removal affect crop production and its response to nitrogen (N) fertilization under various tillage systems. In order to address these issues, agronomist from Iowa State University Extension held forums and surveys to outline farmer’s concerns of crop residue removal for bioethanol production. Extension educators, crop consultants, and other agriculture professionals that work with farmers directly across Iowa have indicated four prevalent concerns; (1) the need for more economical data on bioethanol production, (2) information on the effects of residue removal on soil quality, (3) the cost of nutrients removed with different levels of residue and what it means for future production, (4) and data supporting no-till, specifically on the decomposition of residue, soil temperature, soil moisture, and stand issues (Iowa State University Extension, 2008-2010). The proposed project will address these concerns by assessing the impacts of crop residue removal under different N fertilization rates and tillage practices, and monitoring the resulting impact on corn production. This will allow us to see how much (if any) residue can be removed and still sustain high soil and crop productivity. The focus of this study is to provide research based information for farmers, agronomists, and policy makers in the decision making processes utilizing crop residue for lignocellulosic ethanol production or livestock feed for maximum economic and environmental outcomes.

The objective of this project was to establish coordinated field studies to determine the short-term and long-term impacts of varying corn residue removal and N fertilization rates and tillage systems on soil, air, and water resources. The project had four anticipated outcomes which include reliable estimates of;
(1) amount of C and nutrients removed and returned to the soil by residue,
(2) soil C and N sequestration potential with different residue management practices,
(3) amount of greenhouse gas emissions,
(4) assessing needs for supplemental fertilization of following crops and cost, and
(5) impacts on soil physical properties.