Proceedings
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1. In-Season Nitrogen Fertilization of SoybeanNitrogen (N) fertilization is not a traditional nutrient management practice for soybean production in Iowa. Soybean is a legume plant and is assumed to adequately obtain needed N through symbiotic fixation. However, there has been interest over the years in using N fertilization to increase yield and grain protein due to the recognition of the large N requirement associated with high yields. Depending on the soil residual inorganic N level and soil N mineralization characteristics, approximately... |
2. Corn and Soybean Response to Sulfur Applications on Iowa SoilsHistorically sulfur (S) application has not been recommended on Iowa soils for corn and soybean production. Prior research has not determined a consistent need for S fertilization in Iowa, with field research indicating no corn or soybean yield response to applied S at virtually every site studied (Thorup and Leitch, 1975; Webb, 1978; Alesii, 1982; Killom, 1984; Sexton et al., 1998; Mallarino et al., 2000). The soil supply, in combination with sources such as manure and atmospheric deposition has... |
3. Using Chlorophyll Meter Readings to Determine N Application Rates for CornOne method for refining nitrogen (N) application in corn is use of in-season crop sensing. To aid producers in making decisions regarding N rate adjustments, a calibrated relationship between sensor-derived information and expected N application need should be established. Nitrogen rate trials were conducted at multiple sitcs across Iowa in 2001-2003. Nitrogen was applied at or shortly after corn planting. Minolta SI'AD chlorophyll meter (CM) readings were collected at the R1 growth stage fiom the... |
4. Winter Rye Cover Crop Biomass Production, Degradation, And N RecyclingWinter rye (Secale cereale L.) as a cover crop can take up residual inorganic N between annual row crops and therefore be used to help reduce NO 3--N loss from fields and movement to water systems. However, does the rye N uptake affect N recycling to soil and add to plant available N? The rye carbon:nitrogen (C:N) ratio could also influence N recycling. The objectives of this study were to evaluate rye biomass degradation and N recycling after spring rye termination in a no-till corn (Zea mays L.)... |
5. Corn Residue Harvesting Effects on Yield Response to N FertilizationProducers have many choices of diverse tillage practices for their corn (Zea mays L.) production systems. However, no-till has become an important soil management practice to help reduce water and wind erosion, as well as nutrient runoff, while conserving soil moisture for crop use. No-till systems also help farmers by saving labor and time, as well as reducing farm costs due to less equipment and fuel consumption. Nevertheless, no-till production is typically more successful and has higher crop... |
6. Nitrogen Fertilization Requirement and Corn-Soybean Productivity in a Rye Cover Cropping SystemNitrogen (N) fertilizer inputs for intensive corn-based cropping systems can increase nitrate (NO 3 -N) concentrations in groundwater. Nitrogen tr ansport in surface water to the Gulf of Mexico is also an on-going issu e for the upper Mississippi river ba sin, especially areas with large corn and soybean acreage. Education and policy efforts have focused on i\provement in N application rate, timing, management, and crop N us e efficiency. However, additional means to reduce N loss are needed. Recent... |
7. Quantifying Corn Nitrogen Deficiency and Application Rate with Active Canopy SensorsPrecision agriculture technologies are an integral part of many crop production operations. However, implementation for N application has lagged, primarily due to lack of a viable system for variable N rate decisions. Ac tive canopy sensors have been developed as a tool to determine plant N stress deficiency and provide an on-the- go decision for implementing variable rate. Two general approaches could be implemented. On e is to plan on conducting canopy sensing each year, with a reduced N rate applied... |
8. Dealing with Sulfur Deficincies in Crop Production: The Iowa ExperienceResearch conducted for more than forty years (pri or to approximately 2005) in Iowa rarely noted improved crop yield with sulfur (S) fertilization. Studies during that time period with corn and soybean found yield increase from S fertilizer application only three times out of approximately 200 trials. Research in the early 1980's had also documented sufficient plant available S in the soil profile for crop production on most Iowa soil associations. Results of recent studies (2000- 2005) in corn and... |