Location: Soil, Water & Air Resources Research2013 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:
Objective 1. Studies showed strong pre-existing soil series or landscape effects that dominated changes in mass of various soil organic matter (SOM) fractions due to different corn stover harvest strategies imposed since 2005. However, stover harvest did have a significant effect on the masses of the youngest SOM fractions. Chemical composition of the SOM fractions was not affected by stover harvest. The same SOM fractions were also extracted from a field experiment designed to evaluate a bio-fertilizer. This experiment replaced one in the original project plan that focused on the intensity of crop production input. Chemical characterization of those samples is not complete. Soil aeration strategies for rice were evaluated in field studies for a third year. Aeration effects on rice growth were more visible during the third year than in the first two, indicating a cumulative effect of aeration treatments on soil properties. Two commercially available humic products were evaluated in corn and soybean fields. Root and aboveground biomass responses were monitored throughout the growing season and grain yields from field-scale maps were compared to identify any interactions between the products and soil series. Objective 2. Rainfall simulation experiments were conducted on tilled, non-tilled, and tilled plus biochar plots near Ames, IA, where different stover harvest strategies were also being evaluated. Preliminary results indicate that moderate and high rates of stover harvest (2.0 and 2.7 tons/acre average for five years) increased surface runoff from no-till plots, but had minimal effect on runoff from chisel-till plots with or without biochar amendment. Overall, runoff was 80% greater from chisel than no-till plots. On stover harvest study sites at Morris, MN, earthworm populations were about six times greater and biomass was about 10 times greater in no-till than in chisel-till plots. For both tillage practices, earthworm populations and biomass were about 1.5 to 2 times greater when residue was retained compared to when it was removed. Objective 3. Goals were pursued in conjunction with the Regional Corn Stover Partnership which is currently being summarized for a five-year, multi-location assessment of corn stover harvest effects. Average corn grain yields with conventional management were 171, 174, 200, 177, and 136 bushels per acre (bu/ac) for 2008, 2009, 2010, 2011, and 2012, respectively. The least significant difference (LSD) for these means was 5 bu/ac. Higher plant population using a twin-row configuration and increased fertilizer rates resulted in average yields of 183, 169, 199, 176, and 138 bu/ac, respectively (LSD = 9 bu/ac). There was no significant difference in yield for chisel plow and no-till treatments. 2012 grain yields were much lower for all systems because of the severe drought. Overall, harvesting a portion of the stover resulted in significantly higher grain yield in the subsequent crop. Soil surface cover measurements following no, moderate, or high removal averaged 97, 85, and 70%, respectively, while after fall tillage, surface cover averaged 70, 55, and 48%, respectively.
1. Crop rotation increases grain yield. Producers often make crop management decisions based only on short-term economic factors such as grain price, but to be sustainable, economic, social, and environment impacts of cropping systems need to be understood. To provide information for more sustainable crop management decisions in the Corn/Soybean Belt, yield data from a long-term (>27 years) tillage and crop sequence study near Ames, IA were compiled and analyzed. To account for fluctuations in annual crop price and grain yield throughout the study, average grain prices for a nine-year (2003 to 2011) period were multiplied by crop yield for 1988 through 2006 to determine gross income. After subtracting management costs for the various tillage practices, the results showed that a corn-soybean rotation was twice as profitable as continuous corn. This information will help producers and their crop production advisors make better, more sustainable crop management decisions throughout this geographic region.
2. Soil aeration improves continuous rice production. Earlier work had showed that long-term grain yields for continuous rice in Arkansas decreased more than for rice grown in rotation with soybean. ARS researchers in Ames, IA collaborated with University of Arkansas Research and Extension personnel to identify the underlying cause (i.e., decreased availability of soil nitrogen (N)) and to design field mitigation options that led to better soil aeration and increased N availability during the growing season. In addition to increased productivity, the Arkansas collaborator has determined the aeration treatments also decreased greenhouse gas emission equivalents by more than 90%, decreased fungal disease pressure, and decreased arsenic concentration in the grain, which is crucial for its use in baby foods. This work promises to make continuous rice production more profitable and sustainable in the southern U.S. and in California.
3. Nutrient mining limits no-tillage yields. Slightly lower crop yields have caused producers in the Corn/Soybean Belt to be reluctant to adopt no-tillage practices even though those practices can significantly reduce soil erosion. Soil profile data collected following a long-term (>27 years) tillage and crop sequence study near Ames, IA were compiled and analyzed to determine which factors were responsible for lower crop yields in non-tilled treatments. Soil-test phosphorus (P) and potassium (K) measurements, coupled with calculated P and K removal by grain crops, showed that plant available P and K had been reduced in non-tilled treatments even though fertilizer was applied based on current recommendations. The decreased nutrient concentrations meant the soil was being “mined” by plants and that current fertilizer recommendations, especially with regard to levels of P and K in the subsoil, need further investigation. This information will help producers and their crop production advisors make better, more sustainable soil management decisions throughout this geographic region.Karlen, D.L. 2012. The Birkás influence on international soil management research and education. In: Birkás, M., editor. Soil School: What to learn from and what to teach about soils. Gödöllo, Hungary: Szent Istvan University Press. p. 145-151.