EFFECT OF PHOSPHORUS FERTILIZER DISTRIBUTION IN THE BAND ON GRAIN YIELD AND P UPTAKE OF WINTER WHEAT AND CORN

Phosphorus fertilizer distribution in the band is affected by band spacing, P application rate, and fertilizer P particle size. Twelve experiments were conducted over four years (1983-1986) to evaluate the effect of different factors influencing P fertilizer distribution in the band on grain yield and P uptake. From 1983 to 1985, five field experiments were conducted to determine the effect of P fertilizer particle size on grain yield and P uptake of winter wheat (Triticum aestivum, L.); in 1983, 1984 and 1986 four field experiments were conducted to determine the effect of band spacing of dual-placed N and P fertilizers on grain yield and P uptake of corn (Zea mays, L.); a Field Pot experiment was conducted in 1984 and 1985 to evaluate the effect of P fertilizer distance and distribution in the band on corn P uptake and dry matter production; and in 1986, effect of band spacing, P application rate, delivery tube size and traveling speed during application with a standard squeeze pump was evaluated on distribution of P fertilizer solution in the applied band. The results indicate that phosphorus fertilizer particle size significantly affected grain yield and P uptake of winter wheat. Optimum particle size was about 0.025 mg which is much smaller than P fertilizer particle sizes farmers normally use (about 20 mg). Great surface area of applied P fertilizer at particle sizes smaller than optimum, and also noncontinuous distribution of large particles in the applied band limited the efficiency of these particle sizes. Band spacing of dual-placed N and P fertilizers affected utilization of both nutrients. Effect of band spacing on N and P effectiveness were opposite in that applied P was more effective while N was less effective as the band spacing decreased. Distance that P fertilizer was applied from plants was important only at early stages of growth. Phosphorus uptake increased as spacing between injection points in the applied band increased. This was because as injection point spacing increased, the P target size (two dimensional surface of P affected soil exposed to the root system) increased, resulting in greater root-fertilizer contact. It was also found that P fertilizer solution is distributed as droplets in the band at low P application rates and narrow band spacings. Distance between droplets reduced probability of root-P fertilizer contact and decreased P fertilizer effectiveness. While many factors influence P fertilizer efficiency, results indicate that P fertilizer distribution is a significant factor affecting efficiency in that it influences the probability of root-fertilizer contact