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).

3.Progress Report
Three corn stover harvest strategies were evaluated and compared to a no removal control. The harvest strategies included collecting.
1)all above-ground plant material possible by cutting stalks at a stubble height of approximately 10 cm (whole plant),.
2)the upper-half by height, or.
3)the lower-half by height. Six site-years of data show an average of 3.9 and 4.8 Mg ha-1 of collectable cobs plus plant material from the ear shank upward (upper half) for continuous and rotated corn, respectively. Average nitrogen-phorphorus-potassium (N-P-K) removal was increased by 23, 2, and 29 kg ha-1 for continuous corn and 36, 4, and 27 kg ha-1 for rotated corn, respectively, when compared to harvesting grain only at these Iowa USA sites. Whole plant stover harvest averaged 5.2 or 6.4 Mg ha-1 and increased N-P-K removal to 32-3-32 or 45-4-36 kg ha-1 for continuous or rotated corn, respectively. Collecting only the lower half of the corn plants required a second pass across the field and had a yield of only 1.0 and 1.5 Mg ha-1, respectively. Harvesting corn cobs and upper plant parts increased total carbon removal 1.8 or 2.2 Mg ha-1 compared to harvesting grain only. Structural sugars glucan and xylan accounted for up to 60% of the chemical composition, while galactan, arabinan, and mannose constituted less than 5% of the harvest fractions. We conclude that with current agricultural management practices, a portion of the corn stover being produced in central Iowa fields can be harvested in a sustainable manner. Samples for soil quality assessment have now been collected from 14 of 15 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 carbon and N, nitrate and ammonium N, phosphorus, and diethylene triamine pentaacetic acid (DTPA) extractable micronutrient levels measurements have been completed on samples from five of the sites and are being completed on four more. Sample processing has begun on those collected from the next five sites. Plans are being made to collect samples from the Upper Snake River site in autumn of 2009. Sulfur (S) and P field studies have been implemented and are providing data that is helping attract supplemental funding from the Fluid Fertilizer Foundation. For P, we found that liquid fertilizer dribbled on the soil surface after soybean harvest had moved approximately 10 cm down into the soil. The highest concentrations were found three weeks after application, but at least some of the applied P could still be detected the following spring. Corn crops on Des Moines lobe soils are responding to S fertilizer treatments, presumably because yields have increased, S contamination in the atmosphere has declined, and S has been removed from P fertilizers since many of the earlier S response studies were conducted in the Corn/Soybean Belt.

4.Accomplishments
1. Water Flux To and From the Water Table. The hydrologic term “specific yield” is the amount of water flux to or from a water table that causes a given rise or fall in water table level. However, this value is very difficult to measure. Using automated equipment, we quantified specific yield for a dry period during the early growing season and after physiologic maturity. Specific yield was calculated for both wetting and drying conditions. Rather than being a constant value for a given soil, specific yield depended on the direction of water table flux, whether crops were growing, and the hydrologic history. This information is important for science because rather than using a constant value for specific yield, this study helped identify mechanisms that cause specific yield to vary. After further study, these mechanisms can be incorporated into models that link water flow in unsaturated soil with the water table.

2. Bean Leaf Beetle Information Provided to Organic Soybean Growers. In response to concerns from certified organic producers who were experiencing significant market losses due to seed staining of soybean, we evaluated alternative ways to manage bean leaf beetles, a known vector for the seed-staining bean pod mottle virus (BPMV). From 2000 through 2006, organic-compliant treatments, including insecticidal and soil fertility products in use by organic farmers, were compared in on-farm and experiment-station trials. Two soybean varieties, Northrup-King 2412 (NK2412) and Pioneer Brand 9305 (P9305), also were evaluated for bean leaf beetle populations. Overall, the NK2412 variety hosted fewer beetles although there was not a significant yield effect. None of the organic-compliant treatments provided measurable control of bean leaf beetle populations, nor did they affect beneficial insect populations. Organic soybean yields ranged from 1.8 to 3.7 Mg ha-1 across all years with no effect from treatments. Producers are encouraged to select soybean varieties based on insect pest response and to monitor bean leaf beetle populations to determine effectiveness of this strategy in organic systems.

3. Surface Banding Successful in Midwestern Soils. Phosphorus (P) is an essential nutrient for plant growth and often needs to be applied to the land for optimum crop production. To be effective, however, the fertilizer must increase the amount of plant-available P in the soil, and the plant root system must be able to take advantage of this increase. We found that the P in liquid fertilizer dribbled on the soil surface after soybean harvest had moved approximately 10 cm down into the soil. The highest concentrations were found three weeks after application, but at least some of the applied P could still be detected the following spring. Three years of field research suggest that P applied to the soil surface after crop harvest will move into the profile, where it will be less subject to loss in runoff or by erosion during the winter months. These results will benefit both commercial growers and the fertilizer industry by providing nutrient management alternatives that maximize crop utilization and minimize potential nutrient losses.

4. No-Tillage Augmented by Diversified Crop Rotations. Surface runoff, soil fertility, and crop yields were evaluated for a no-tillage corn and soybean rotation and a no-tillage contour strip-cropping with a corn-soybean-corn-alfalfa rotation on deep-loess soils in western Iowa. No-tillage plus the contour strip-cropping reduced runoff by more than 50% compared to no-tillage alone despite having three of the most intensive rainfall events in the 40-year history of the research site. This suggests that combining no-tillage with more diverse crop rotations can reduce the potential for flooding in agricultural watersheds. Using Late-Spring Nitrate Testing (LSNT) reduced annual fertilizer recommendations by 22 to 34% compared to the long-term average (178 kg N ha-1), thus demonstrating a significant economic savings for the producer and reducing the potential for nitrogen (N) leaching. Improved genetics and better crop management improved average corn yield by 2 Mg ha-1 compared to the long-term average for continuous corn (7.2 Mg ha-1) on these two field-scale watersheds. These results will benefit growers and conservationists by providing improved management practices for highly-erosive soils.

6.Technology Transfer

Number of Other Technology Transfer

5

Review Publications
Karlen, D.L., Andrews, S.S., Zobeck, T.M., Wienhold, B.J. 2008. Soil Quality Assessment: Past, Present, and Future. Electronic Journal of Integrative Biosciences. 6(1):3-14. Available: www.clt.astate.edu/electronicjournal.