Adição de ácido cítrico mais ativador enzimático e calagem na disponibilidade e movimentação de íons no solo

Abstract

The increase of the weathering cause changes in some soil properties, turning it more electropositive and with greater capacity of adsorving ions such as phosphate. The different management systems to which the soil is submitted can increase or diminish the P fixation, depending on the transformation degree and interaction among the components added by the management and by the soil matrix by itself. The adoption of management systems that may offer an increase in the organic matter level, or of a fraction of it (organic acids, for instance), can contribute to the reduction of the P adsorption in the surface of the iron and aluminum oxides. Several soil properties affect these relationships, being the most important: the mineralogy, the texture, the pH, the zero charge point, the organic matter, the kind of organic acids, and the microbial activity. The present work aimed to evaluate the interactive effects between acid citric doses plus enzymatic activator and the availability of some phosphorus forms in a soil of strong clay texture and in a medium texture soil, submitted to the application of superficial and incorporated liming. The work was conducted in green house in the Faculdade de Ciências Agrárias (FCA), of the Universidade Federal da Grande Dourados (UFGD). Two types of soil were utilized: Distroferric red Latossol, with strong clay texture, and Distrofic Red Latossol, medium texture. The factors studied in each kind of soil were: two types of liming(surface liming and incorporated liming); six doses of citric acid plus enzymatic activator (0, 1, 2, 3, 4 e 5 kg ha-1); four depths (0-50, 50-100, 100-150, 150-200mm). The soils were submitted to the Pi, Po, Pt and Prem analyses, and in the routine analysis P (Melich 1) was determined. In the conditions in which this work was conducted it is possible to be concluded that: the application of citric acid plus enzymatic activator doses induces to reactions in the soil, and the Pi and Pt levels depend on the soil texture and liming form; in the soil with heavy clay texture, the more elevated levels of Pi and Pt are, in general, found when the liming is incorporated, while for the medium texture soil this occurs toe the superficial liming; in the medium texture soil the Prem levels vary according to the liming form and the citric acid plus enzymatic activator doses.