CORN YIELD AND PHOSPHORUS UPTAKE WITH BANDED UREA AND PHOSPHATE MIXTURES

Low fertilizer P use efficiency is a problem in crop production on aci d soils, but efficiency can be affected by methods of fertilizer appli cation. A field experiment was conducted on two eastern Canadian soils (fine-silty to fine, mixed, frigid Typic Humaquepts) with different p H (5.0 and 6.0 initially) to evaluate the effect of banding different rates of urea with acidic P fertilizers on corn (Zea mays L.) yield an d fertilizer use efficiency. Three rates of urea (0, 30, and 60 kg N h a-1) banded with two sources of P (triple superphosphate [TSP] and mon oammonium phosphate [MAP] at 38.7 kg P ha-1) or alone without P fertil izer, as control, were studied in 1990. In 1991, three rates of TSP (0 , 19.4, and 38.7 kg P ha-1) were used in combination with the same thr ee rates of urea to determine the effect of banding ratio of urea-N/TS P-P. The residual fertilizer effects of the 1990 treatment were invest igated in 1991. Banding urea with TSP or MAP increased soil extractabl e P (Mehlich III). At the six-leaf stage, plant P concentrations and d ry matter yield increased linearly with both banded N and P in the Ste . Rosalie soil, and quadratically in the Ormstown soil. Total N and P uptake by corn increased in both years by banding urea with TSP or MAP , and fertilizer P use efficiency increased by 40 to 80%. Urea banded with P increased grain yield in both soils. No interactions were found between banded N rates and P sources in 1990, and between banded N ra tes and P rates in 1991. Greater residual effects of P fertilizer were found on grain yields and P uptake where P was banded with urea compa red with no urea.