DETERMINATION OF THE MOST EFFICIENT PHOSPHORUS PLACEMENT FOR FIELD-GROWN MAIZE (ZEA-MAYS L) IN EARLY GROWTH-STAGES

Field experiments were conducted in 1988 and 1989 to determine the mos t efficient phosphorus (P) placement for P absorption by maize (Zea ma ys L.) in early growth stages. The treatments consisted of four rates of applied P (0, 25, 50 and 100 kg P ha-1 mixed with 3, 6, 12 and 25 % of the soil volume in the row. Shoots and roots were sampled at 3- to 4-leaf, 6-leaf, and 8- to 9-leaf stages. The roots inside and outside the zone of P fertilization were sampled separately. There was no evi dence of root proliferation in the fertilized zones, even with the 100 kg P ha-1 rate mixed with 3% of the soil volume. There was a signific ant response of shoot dry matter, shoot P concentration, shoot P uptak e, and root growth to applied P. Shoot P concentration and shoot P con tent increased as the volume of soil with which fertilizer P was mixed decreased. Mixing 100 kg P ha-1 with 3-6% of the soil volume resulted in the highest shoot P content in the early growth stages. There was no evidence that fertilizing a greater proportion of soil than the con ventional band method will result in higher P uptake of maize in early growth in the soil studied. Because the soil in the study had a relat ively low P adsorptive capacity, this conclusion is likely valid for a broad range of soils, which have a greater P adsorptive capacity.