NO-TILL WINTER-WHEAT RESPONSE TO PHOSPHORUS PLACEMENT AND RATE

Phosphorus deficiency of winter wheat (Triticum aestivum L.) is common in the central Great Plains. Acceptance of reduced and no-till systems for wheat production has made soil incorporation of broadcast P fertilizer more difficult. This field study evaluated the effectiveness of P placement methods (surface broadcast with and without incorporation and banded below the seed zone) for no-till winter wheat production at rates of 0, 34, 67, 101, and 134 kg P ha-1 in 1986 and 1987. Subplots of 0 and 56 kg N ha-1 were included with each P rate. A Rosebud-Escabosa loam soil (fine-loamy, mixed, mesic Aridic Argiustoll-Calciustoll) with a NaHCO3-extractable P level of 10 mg P kg-1 soil (medium soil test level) and a pH of 7.8 was used. Phosphorus placement had no significant effect on grain yield. Grain yields increased curvilinearly with increasing P rate up to 101 kg P ha-1 for both broadcast and banded treatments. Straw yields also increased curvilinearly with increasing P rate. Nitrogen fertilization enhanced grain protein by 6% and also grain P uptake. Total P uptake by grain increased with increasing rate of P application. Broadcast applications of P without incorporation under no-till conditions effectively incased winter wheat yields on a soil testing medium in available P. When sufficient P was applied to correct P deficiency in winter wheat, method of placement had little effect.