Cobre e zinco em latossolo adubado com dejeto liquido de suíno e cultivado com grama-missioneira-gigante

Abstract

The effects of pig slurry (PS) application on copper (Cu) and zinc (Zn) availability on soil are poorly understood, although such availability is important for plant nutrition and a concern related to environmental contamination. The aim of this work was to evaluate the affect of PS rates on Cu and Zn availability of an Oxisol cultivated with giant grass-missionary pasture, after four years of fertilization with PS. Field trials were located at the Research Center of EPAGRI CEPAF, in Chapecó, in western Santa Catarina, Brasil. A randomized complete block design was used. The treatments were PS rates (average of four years of application: 0, 48, 96, 144, 192 and 240 PS m3 ha-1 yr-1), broadcast applied, after each pasture cutting. After four years of PS application and of pasture growth, we evaluated the effect of PS rates on the Cu and Zn availability, and on other chemical attributes of 0-5, 5-10, 10-20, 20-30 and 30-40 cm layers of the soil. The soil contents of Cu and Zn were evaluated by using the following approaches: sequential extraction, in order to estimate the soluble, exchangeable, mineral, organic and residual fractions; hydrochloric acid extraction, in order to estimate the available content; USEPA 3050 B method, in order to estimate the soil contamination; and extraction with nitric, fluoridric and perchloric acids, in order to estimate the total concentration. A correlation between the results and the concentration and amount of Cu and Zn of pasture shoot was evaluated. The phosphorus and organic matter content, on 0-10 cm layer, increased with the doses of DLS. Independent of doses, the application of PS increased the content of Cu and Zn (extracted with HCl) and decreased the content of potassium, on 0-5 cm soil layer. Fertilization with PS did not contaminated the soil with Cu and Zn (extracted with method 3050B) and increased the Cu content of the organic fraction (linear response to doses) and the Zn content of the mineral fraction (no dose response), of the 0-5 cm soil layer 0-5 cm. It did not affect the other fractions of these metals. For soils with high doses and continued application of DLS, monitoring the content of these metals is recommended. The higher extraction of Cu from the the pasture shoot was related with the higher content of this metal extracted with HCl and from the organic fraction of the soil (0-5 cm). The content and the amount of Zn in the pasture increased with the contents of this metal in exchangeable, mineral, and organic fractions of the 0-5 cm soil layer