Liberação de potássio em latossolos tratados com resíduos orgânicos
The K release rate varies amongst organic residues and it is dependent on the humification degree, chemical composition, content and forms of K present in the analyzed organic material. This study was carried out in order to evaluate the potential and the K release of different organic residues incubated with sand and Latosol samples. The experiment was conducted at the Soil Science Department/Federal Uninersity of Lavras, from July 2007 to April 2008. The following organic residues/fertilizers were used: sewage sludge of industrial and residential origins, chicken manure, swine manure, quail manure, equine manure, bovine manure, garbage compost, commercial organic substratum, turf and organic compost. The treatments tested were: incubation of residues samples with sand washed with acid solution; incubation of organic residues with Yelow-Red Latossol samples; and with Red Latossol distroferric samples. Soil and sand/organic residues were incubated during 270 days in PVC columns. The K release was evaluated in intervals of 15 or 30 days, through the analysis of K in leachates inaflame fotometer. The process of K release is divided in two different phases: one of approximately thirty days, with intensive K release, and the other one, in the sequence, in a slower rate, with a tendency of reduction and stabilization of the amounts of K released. The organic residues/manures presented different patterns of K release, so that the manure of equine, quail manure, chicken manure and organic substratum liberated K in larger amount. The amounts of K released are regulated by the total and soluble contents of K in the organic material analyzed.