NACAA

IMPORTANCE OF STARTER PHOSPHORUS FOR GRAIN YIELD IN SOFT RED WINTER WHEAT

Abstract:

Nitrogen (N) and phosphorus (P) are often applied as starter for winter wheat. In recent years, P fertilizer has greatly increased in price where producers have considered only applying starter N. The objectives of this study were to determine the importance of P as a starter fertilizer and to measure the effects that P starters may have on grain yields. In Fall 2008, medium-maturity variety ‘Hopewell’ was established into soybean stubble on the OARDC Northwest and Western Research Station near Custar and South Charleston, Ohio, respectively. Treatments included urea-ammonium nitrate alone at 25 lb acre-1 N and six P products (25 lb acre-1 N and 65 lb acre-1 P rates) as DAP, monoammonium phosphate (MAP), DAP plus sulphur (S), MAP-S; and proprietary P, P-S, and P plus zinc (Zn) products. Supplemental S was at the 10 lb acre-1 rate. Experimental design was a completely randomized block replicated four times. Analysis was a simple ANOVA. Grain yields were similar among all P products at both locations. However at the South Charleston location, the starter N product alone was significantly lower in yield (15 - 20%) than the P products. Soil test P levels were at maintenance level at the Custar site, but slightly below the critical soil test level at South Charleston. Starter P appears to be important for grain yield on soils at or below the critical soil test level. Regardless of soil test P, selection of P source or additional S or Zn should not affect yield.