Corn and Soybean Response To Phosphorus Placement Under Minimum Tillage System.

Producers often question the need for better fertilizer placement methods in reduced tillage systems.  The objective of this study was to evaluate the effects of different placements and rates of phosphorus fertilizers in corn (Zea mays) and soybean (Glycine max).  The study was established at 3 locations in the spring of 2005 (8 years).  This paper focuses on one irrigated location.  Fertilizer placements included: starter, broadcast, deep band, and various combinations of starter with broadcast or starter with deep band.  Total fertilizer rates included: 0, 22, 45, and 90 kg P₂O₅ ha^-1.  The experimental design was randomized complete block with four replications.  Corn early growth biomass was evaluated at the V6 growth stage, including whole plant tissue phosphorus concentrations.  Corn ear leaf tissue samples were collected at the VT-R1 growth stage and analyzed for phosphorus concentration.  Soybean uppermost fully open trifoliate tissue were also collected at the R1-R2 growth stage and analyzed for phosphorus concentration.  Corn grain yield and soybean seed yield were evaluated at the end of the growing season.  Results showed significant differences in corn early growth, early season P concentration and uptake, ear leaf P concentration, soybean leaf P concentration, as well as corn and soybean yield response to phosphorus fertilization.  Differences in corn early growth, P uptake, ear leaf P concentration, and soybean tissue P concentration were also significantly affected by fertilizer placement.