Residual Effects of Various Phosphorus Application Methods on Winter Wheat and Grain Sorghum
The amount of residual P from previous applications and the performance of fertilizer P can be affected by application method. This study was conducted to determine the effects of different methods of P application on grain yield, yield components, fertilizer-P efficiency, P-utilization efficiency (kg grain per kg P uptake), and residual P in two cropping systems — a wheat (Triticum aestivum L.) and grain sorghum [Sorghum bicolor (L.) Moench] system on Pawnee soil (fine, montmorillonitic, mesic Aquic Argiudoll) and a wheat-fallow-wheat system on Keith soil (fine-silty, mixed, mesic Typic Argiustoll). Methods of P application to wheat included broadcasting and knifing in the fall and spring, and seed placement. Phosphorus applied to wheat and its residual effects were determined on sorghum following wheat and wheat following fallow. On sorghum, spring row and knife-applied P methods were compared with residual treatments. For wheat production, P knifed in the fall and seed application were equally effective. Both were more effective than other application methods for grain yield, P uptake, and fertilizer efficiency. Fertilizer efficiency was increased from 5.5% for broadcast to 36% for knifed and 40% for seed application. Spring knifed and row applications of P were equally effective for sorghum. Knifed P, placed below tillage depth with little disturbance of the band area, resulted in greater residual value for grain sorghum following wheat than either seed or broadcast P. In the wheat-fallow-wheat system, the knifed spring P, which had the shortest time of soil contact, had significantly greater residual value than other methods. Wheat had much higher fertilizer-uptake efficiencies, but was only about half as effective as sorghum in P-utilization efficiency. This study indicated that undisturbed fertilizer P bands have more residual value than either seed-placed or broadcast P, which can differentially influence the P-fertilizer requirement for succeeding crops.
Copyright © .