Controle da reação do solo e otimização da adubação fosfatada no cultivo do meloeiro

Abstract

The quality of agricultural soil is constantly influenced by natural causes and anthropic activity. Thereby, two studies were performed, the first with the objective of evaluating soil pH reaction with the use of sulfuric acid in irrigation water and the biological oxidation of sulfur. The second study aimed to evaluate dosages of phosphorus combined with use of acidifying products in the soil with cultivation of melon in a greenhouse to evaluate the growth and production variables. The study in the incubation condition occurred with three types of soils: Argissolo Vermelho "woods", Argissolo Vermelho "cultivated" and Cambissolo Háplico, five doses of sulfur (0, 25, 50, 100 and 200 kg ha-1) and three volumes of bacteria (1, 2 and 3 ml). Another soil incubation experiment, was carried out using five doses of sulfuric acid in the irrigation water (0, 30, 50, 70 and 90%) in the same soils of the sulfur incubation. Two soils were used in the greenhouse: Argissolo Vermelho "woods" and Cambissolo Háplico, four doses of phosphorus (0, 49.4, 77.9 and 106 kg ha-1 of P2O5) and three treatments for soil pH (no correction, sulfuric acid and sulfur plus A. thiooxidans). The incubation experiment showed that sulfur inoculated with the bacteria and the use of sulfuric acid were efficient in soil pH control. Among the evaluated soils, the Cambissolo Háplico presented lower variation in relation to Argissolo Vermelho. In both treatments there was increase in pH regarding to its initial value. The sulfur inoculated with the bacteria and the use of sulfuric acid are efficient in the control of the soil pH. The soil pH correction methods not affect the commercial production of the melon. In order to meet the commercial production of fruits it is recommended apply no control methods to correct soil pH, and the dose of 44.9 kg ha-1 of P2O5. Soils no recently cultivated and under the fertility conditions meet in this research, can be cultivated with melon irrigated without loss for growth and production, by a cycle. The soil pH control methods had no influence the biometric characteristics and production characteristics of both soils. The ideal phosphorus dose to meet growth and production conditions in the melon cultivation was 49.4 kg ha-1 of P2O5 jointly with no soil pH correction