Optimization of Nitrogen and Phosphorus Fertilizer Timing and Placement in Strip-till Corn Systems.

Nitrogen and phosphorus management are heavily dependent on tillage type. Many long-term no-till producers, confined largely to surface application, struggle with nutrient stratification. Strip-till systems offer alternative nutrient placement options; this study focuses on pre-plant mixing of the upper-zone soil in the future corn rows while concurrently incorporating urea ammonium nitrate (UAN) and/or a commercial granular P-dominated fertilizer (MicroEssentials¨ SZª). Different tillage timings (fall, spring or fall and spring), nutrient placements (zone-banded or broadcast), and starter applications (starter or no starter) were evaluated by measuring soil nutrient distribution, plant nutrient uptake, and grain yields. Corn was grown in rotation with soybean on a dark prairie soil with an average soil-test P concentration of 16 ppm to a 20-cm depth. In 2013 one fall strip-till pass with the SoilWarrior¨ (SW), a coulter-based strip-till unit, increased grain yields 435 kg ha-1 relative to no-till. Soil test levels confirmed zone-banded dry fertilizer was incorporated in the corn row to a depth of approximately 5-cm; however, there was no consistent plant uptake or grain yield advantage with either P application or timing method. No distinct advantage was found by zone-banding 44 kg N ha-1 of UAN just before planting versus applying a full N rate (180 kg ha-1) at sidedress. Starter application was associated with higher N and P uptake at V6 but whole-plant R6 and yield measurements did not reflect the early uptake gain. This presentation will also include pertinent results from the second year trial in 2014. Thus far the advantage of strip-tillage itself is clear but the optimum N and P fertilizer program with strip-till is less clear.