Phosphorus Residue of Triple Superphosphate Applied In Furrow According to Time, Doses and Initial Growth of Maize (Zea mays, L.).

The experiment was carried out under greenhouse conditions to study the effects of doses and several periods of contact between the granular triple superphosphate (TSP) applied in the furrow and the Ultisol Paleudult. We evaluated the initial growth of the maize, the residual contents of P, the phosphorus total (P_TOTAL), the phosphorus soluble in neutral ammonium citrate + water (P_NAC) and the water-soluble phosphorus (P_H20). The fertilizer was placed into flexible cylinders made of shade net fabric put into the soil to simulate the banded application. The experimental design was the complete randomized blocks in the factorial arrangement (6 x 6) + 1 with three replications. The maize plants were cultivated in plastic pots with 7 kg of air dried soil. We applied six doses of P (12.5; 25; 50; 100; 200 and 400 mg P.kg^-1 soil) from triple superphosphate, during six periods of contact (30, 37, 45, 60, 120 and 210 days) plus a control without the fertilizer. The amount of P in the residues was proportional to the applied dose and the estimates decreased with the time. The variation in the residual mass over the time indicated that the phosphate dissolution was much more than an isolated process. We detected interaction between the fertilizer and the soil with significant variations in the available P along the time. The P_TOTAL, P_NAC and P_H20 concentrations in the residue increased with the dose and decreased with the time. The insoluble proportions of P in the P_TOTAL increased with the time, unlike the P_NAC and P_H20. The maize growth and the phosphorus absorption increased with the dose and decreased with the time.