Wednesday, November 15, 2006

Effect of N Fertilizer Source, Rate, Placement and Application Timing on Hard Red Winter Wheat Yield and N-Use Efficiency.

Matthew Stowe1, Richard Koenig1, David Huggins2, and John Reganold1. (1) Washington State Univ, Dept of Crop and Soil Sciences, PO Box 646420, Pullman, WA 99164-6420, (2) USDA-ARS, Washington Univ, 215 Johnson Hall, Pullman, WA 99164

The development of management strategies to improve nitrogen-use efficiency (NUE) of wheat is required to reduce the cost of fertilizer inputs and N pollution. The main objective of this study was to assess the effects of N source, rate, placement and timing on grain yield, grain protein and NUE of hard red winter wheat in field experiments conducted in southeastern Washington during 2004-05 and 2005-06. Treatments included: (1) controlled release (CR) and conventional urea fertilizer applied at rates of 0 to 280 kg N/ha placed in a band beneath the seed row; (2) select CR and urea N placement treatments (broadcast or banded beneath or with the seed) applied at 168 kg N/ha; and (3) urea application timing (at planting, late fall, early spring, and combinations) applied at 168 kg N/ha. Grain yield and plant and soil N were measured to assess NUE components. The grain yield response to N rate was quadratic but there was no interaction between urea source and rate, and there was no significant difference among application timings of conventional urea. The CR deep band treatment produced 1360 kg/ha more grain than CR broadcast (p < 0.05); otherwise there were no differences in grain yield among placement treatments. Preliminary analyses suggest there was no interaction between urea source and rate for the following dependent variables: (1) grain N uptake; (2) NUE; (3) N retention in the profile; and (4) N uptake efficiency at p < 0.05. More detailed analyses and second year results from the study are pending. Preliminary results suggest few differences between conventional and CR urea when banded beneath the seed row in this study.