2008 Annual Report
1a.Objectives (from AD-416)
1) Assess and monitor the effectiveness of past, present, and future soil resource management practices using the Soil Management Assessment Framework..
2)Develop innovative, ecologically-based crop and soil nutrient management practices for enhanced productivity and negligible off-site agricultural impacts..
3)Conduct field-scale evaluations of selected conservation practices to support the Conservation Effects Assessment Project (CEAP) and quantify landscape effects on soil water and nutrient availability.
1b.Approach (from AD-416)
This project utilizes an ecological soil management approach to place a greater emphasis on measuring and understanding the interactions that result from the human decision-making processes regarding soil resources, land use, tillage, crop selection, and other management practices. Our emphasis on the expected and non-expected responses and interactions is important because many of our current soil and crop management decisions are not sustainable as evidenced by erosion, decreased soil organic matter content, contamination of surface and ground water resources, compaction, and/or acidification. The project is designed around three objectives that focus on (1) evaluating and improving two assessment tools, the soil conditioning index (SCI) and the soil management assessment framework (SMAF), (2) developing improved nutrient, tillage, carbon, and crop management practices that will enhance productivity without negative off-site consequences, and (3) evaluating existing and new conservation practices at the field and watershed scale. Use, evaluation, and further improvement in the SMAF as a tool to assess the soil quality effects of soil management practices provides a common thread throughout the entire project. Studies at multiple scales will provide information that can “contribute to the efficiency of agricultural production systems (Strategic Plan Objective 1.2) and "provide science-based knowledge and education to improve quality and management of soil, air, and water resources" (Strategic Plan Objective 5.2). Our primary customers include the NRCS, DOE, conventional and organic producers, fertilizer industry, and scientific community. The project also provides information for three cross-location projects identified in the 202 Action Plan, one Cross-Location Education and Research (CLEAR) project, the inter-Agency Conservation Effects Assessment Project (CEAP).
Harvesting the top 50%, bottom 50%, or 90% of corn stover from continuous and rotated corn for three years showed no significant difference in corn grain yield. Low soil-test phosphorus (P) and potassium (K) presumably caused soybean yield to be significantly lower following 90% removal. Average stover removal with a one-pass combine was 2.0, 0.6, and 2.6 tons/acre of stover, respectively. Harvesting the top 50% increased average nitrogen (N), P, and K removal by 30, 3.3, and 28 kilograms per hectare (kg/ha). Based on sugar analysis, the minimum ethanol selling would have been $1.11, $1.16, and $1.10 per gallon, respectively.
A core 25-acre field study with two tillage and three stover harvest rates was initiated. A “twin-row” planting with higher fertilizer rates was added to increase grain and stover production. A third set of chisel-tilled plots received biochar at rates averaging 9814 and 118440 kg/ha. Annual and perennial cover crop treatments were also included to partially offset carbon (C) loss due to stover harvest. This project contributes to the Renewable Energy Assessment Project (REAP) and SunGrant Regional Partnership studies.
Samples for soil quality assessment have been collected from 9 of 14 Agricultural Research Service (ARS) Conservation Effects Assessment Project (CEAP) benchmark watersheds. Texture, bulk density, water stable aggregation, microbial biomass carbon, acidity (pH), electrical conductivity (EC), total organic C and N, nitrate and ammonium N, P, and diethylene triamine pentaacetic acid (DTPA) extractable micronutrient levels measurements are nearly complete on samples from five of the sites in Oklahoma, Texas, Georgia, and Iowa (two sites). Samples were collected during FY08 in Indiana, Mississippi, New Hampshire, and Maryland and similar analyses are in progress.
Studies on pedo-transfer functions to improve the Soil Management Assessment Framework (SMAF) scoring function for plant-available water content were terminated after finding the various functions available in the literature produced very different results. Adjustments to account for upward water movement were explored but none gave the accuracy needed because an accurate method for assessing plant-available water, to which improvements for upward water movement could be made, does not exist. The SMAF scoring function for plant-available water was converted from a step-wise to a continuous function.
A research site to quantify urban soil management effects on soil water relationships has been established near Ankeny, IA. Collaboration with researchers from Coshocton, OH, on their urban site has been established and soil cores have been collected for analysis. A laboratory column study is also being set up to provide additional data for computer simulation models.
(NP202, Components 2, 4, 5, and 6)
Fluid fertilizer helps sustain soils used for biofuels production. Growing crops for bio-fuel production has attracted the attention of many producers – especially in the Corn Belt states. Both corn grain and stover are being evaluated as potential bio-fuel feedstocks. Unfortunately, our understanding of the short- and long-term effects of removing both corn grain and stover on soil nutrient cycling, physical properties, and biological activity is limited. Several sulfur (S) fertilizers as S sources for corn were evaluated. An application of 30 pounds (lb) S/acre (A) increased early-season growth and plant S concentrations compared with untreated areas, and increased grain yield by up to 10 bushels (bu)/A. Continued erosion of high-fertility hill slope soils, fewer S impurities in fertilizers, and decreased atmospheric deposition of S throughout the upper Midwest are among the reasons for this response. (NP202, Component 4)
Shallow groundwater influences plant-available soil water in rolling landscapes. Depressional and toeslope landscape positions have more shallow, less variable water table depths than shoulder and backslope positions because of subsurface lateral water movement. Plant-available water is increased through capillary rise from shallow water tables, but current water flux and uptake models generally do not account for this. This study showed that even on days without rain, considerable water moved into the root zone during the growing season, especially in toeslope positions. It provides a better understanding of field scale drainage, water table recharge, and capillary rise, thus providing a basis for more accurate water flux modeling. (NP202, Component 2)
Organic fertilization and cover crops influence organic pepper production. Certified organic vegetable producers are required to implement a soil-building plan that increases soil fertility. Using combinations of organic fertilizers and cover crops is one way to achieve this goal. This study evaluated several soil fertility practices for producing organically grown bell peppers in southeast Iowa. Using cover crops and composted animal manure increased soil organic matter and available nitrogen. Pepper yield and quality were consistent with soil fertility, except when cover crops were not adequately incorporated into the soil. (NP202, Component 4 and the Agricultural Research Service (ARS) Organic Research Action Plan)
Hilltop soil management could reduce nitrogen (N) and phosphorus (P) losses.
Current corn and soybean management practices do result in leaching of nitrate N and loss of P through erosion and overland flow. An assessment of soil quality indicators in the Iowa River South Fork Watershed showed the lowest ratings for soil organic matter with the total organic carbon (TOC) and carbon:nitrogen (C:N) ratios being the lowest in upper landscape positions. This indicates erosion and nitrate leaching are more likely to occur in those areas, thus emphasizing the need for better conservation practices such as perennial or cover crops, no-tillage, and other management practices that can improve soil quality. (NP202, Component 5)
|Number of Non-Peer Reviewed Presentations and Proceedings||5|
|Number of Newspaper Articles and Other Presentations for Non-Science Audiences||2|
|Number of Other Technology Transfer||2|
Martens, D.A., Jaynes, D.B., Colvin, T.S., Kaspar, T.C., Karlen, D.L. 2006. Soil amino acid enrichment following soybean in an Iowa corn-soybean rotation. Soil Science Society of America Journal. 70:382-392.
Tomer, M.D., Moorman, T.B., Kovar, J.L., James, D.E., Burkart, M. 2007. Spatial Patterns of Sediment and Phosphorus in a Riparian Buffer, Western Iowa. Journal of Soil and Water Conservation. 62(5):329-338.
Wilhelm, W.W., Johnson, J.M., Karlen, D.L., Lightle, D. 2007. Corn Stover to Sustain Organic Carbon Further Constrains Biomass Supply. Agronomy Journal. 99:1665-1667.
Karlen, D.L., Tomer, M.D., Neppel, J., Cambardella, C.A. 2008. A Preliminary Watershed Scale Soil Quality Assessment in North Central Iowa USA. Soil & Tillage Research. 99:291-299.
Delate, K., Cambardella, C.A., Mc Kern, A.C. 2008. Effects of organic fertilization and cover crops on organic pepper production. HortTechnology. 18(2):215-226.