Location: Soil, Water & Air Resources Research2011 Annual Report
1a. Objectives (from AD-416)
1) Quantify the effects of soil management practices and amendments, including humic substances, to enhance soil organic matter and carbon and nitrogen dynamics for improving soil productivity. 2) Measure the impact of soil management practices that will increase soil aggregation, reduce compaction, affect crusting, and minimize trace gas exchange processes within Midwestern soils for enhanced soil productivity and environmental quality. 3) Develop sustainable biofuel feedstock production systems using soil quality assessment tools to ensure the practices sustain productivity and protect soil, water and air resources.
1b. Approach (from AD-416)
Biochemical analyses will be used to distinguish between labile and recalcitrant fractions of soil organic matter to improve the knowledge base regarding the effects of residue management on short-term soil processes (nutrient cycling, soil structure, and crust formation) and long-term carbon sequestration. This basic knowledge will then be applied to current production problems associated with providing sustainable supplies of bioenergy feedstock and enhancing grain yields to help meet ever-increasing food and feed demands. Utilizing corn, soybean, and small grain (i.e. rice, rye, and wheat) cropping systems, soil management practices to increase corn growth and grain yield will be evaluated in multiple field experiments. Various single-pass corn stover harvest and crop management strategies, cover crops, crop rotations, and tillage intensity will provide the crop production systems within which soil quality will be measured and the chemical nature and cycling of soil organic matter fractions will be quantified using seasonal analyses of amino acids, amino sugars, carbohydrates, phenols, and fatty acids. Effects of soil aeration on the decomposition of crop residues and the subsequent quality of soil organic matter, efficiency of nitrogen (N) cycling, and crop grain yield will be quantified in these experiments. The soil biochemical measurements coupled with soil physical process measurements will be used to augment the knowledge base related to soil quality assessment at plot scales for potential extension to field scale assessments. Project results will quantify the effects of crop residue management on soil physical and biochemical properties contributing to economic yields and long-term sustainability of major cereal cropping systems, leading to improved soil management practices.
3. Progress Report
This project replaces 3625-11120-003-00D and became active in April 2011, so most accomplishments for FY11 are reported in the final report for 3625-11120-003-00D. Since its inception, analyses for amino acids and fatty acids were developed and calibrated with existing methods. The first growing season for rice was largely completed with field evaluation of soil aeration strategies. The sustainable feedstock studies were continued and soil physical data examining draft forces two and one-half years after about 4 or 8 tons per acre of biochar application were examined. There were no significant differences between those treatments, a control, or the high-population intensive management scenario. There were also no detectable significant differences in soil draft following two stover harvests.
1. Rye cover crops have a short-term effect on soil organic matter. Cover crops can improve soil by taking up residual nutrients, protecting the surface from wind and water erosion, and reducing runoff, but results have been mixed regarding their ability to sequester carbon in the soil. To answer this question, Agricultural Research Service (ARS) researchers at Ames, Iowa, collected soil from a corn field that had a rye cover crop and obtained several organic fractions using a series of flotation, sieving, and chemical extractions. Amino acids and plant carbohydrates were the primary compounds being formed as the cover crop decomposed. These compounds are considered to be young soil organic matter fractions because they are easily decomposed. Samples collected two months after the cover crop was incorporated had greater quantities of amino acids and carbohydrates than the control, which did not have a rye cover crop, but these effects diminished after a few months. These results confirm that cover crops can influence nutrient cycling and can thus affect fertilizer management decisions, but additional studies will be needed to quantify their effect on long-term carbon sequestration.