Soil phosphorus availability and estimation of optimum levels of applied phosphate for tomato in the sub-middle São Francisco river Valley

Abstract

Soil phosphorus availability was evaluated by Mehlich and Bray 1 methods in a sandy Red-Yellow Latosol of the São Francisco River Valley, from 1982 to 1983, to estimate optimum levels of phosphate fertilizer for tomato (Licopersicum esculentum, Mill). Different levels of phosphorus in the soil were adjusted by application of different quantities of phosphate in the form of triple superphosphate in advance. Significative correlations of the amount of soil phosphorus were obtained with the levels of phosphate applied and the yield of tomato. The amounts of phosphorus in the soil estimated by Mehlich and Bray 1 methods were respectively classified as: very low - for less than 5 ppm and for less than 7 ppm; low - from 5 ppm to 10 ppm and from 7 ppm to 12 ppm; medium - from 11 ppm to 16 ppm and from 13ppmto 18 ppm; high - from 17 ppm to 29 ppm and from 19 ppm to 31 ppm; and very high - for more than 29 ppm and for more than 31 ppm. Levels of estimated phosphate to be applied in the furrow to obtain the expected optimum productivity for very low, low, medium, high and very high amounts would be 120, 100, 70, 30 and 0 kg/ha of P₂O₅, respectively.