Nitrogen mineralization in soils fertilized with vinasse

Abstract

In areas fertilized with vinasse, the total amounts of N applied are relevant, but in general it is not known how much N is available, neither the transformations that it causes in the N of the soil. It is only known that there is a need to complement N doses for sugarcane with industrial fertilizers. In vinasse, N predominates in organic form and needs to be mineralized to be absorbed by plants. In order to obtain estimates of the mineralized N from the vinasse application it is necessary to determine the rate of mineralization in the laboratory and in the field. With the present project we intend (I) to evaluate the N mineralization rate in a laboratory incubation test using soils treated with vinasse, and (II) to correlate the mineralizable N with N absorbed by sugarcane plants. Two experiments will be carried out under controlled conditions, both combining three soils (sandy, sand-clay and clayey) collected in the 0 to 20 cm layer and three doses of vinasse (0, 75 and 150 m3 ha-1). In the experiment in pots will be used a completely randomized design with four replicates. In the pots will be transplanted two pre-sprouted sugarcane seedlings, which will grow for 60 days. At the end of the experiment the N absorbed by the plants (Nabs) will be obtained. The mineralized N will be evaluated at 14; 21; 28; 35; 42; 49; 56 and 63 days of incubation. The obtained data will be adjusted to the exponential equation of first order kinetics to obtain the potentially mineralizable N (N0) and the mineralization constant (k), and the N0 and N mineralized accumulated at 63 days will be correlated to the Nabs by the sugarcane plants.