Availability of Phosphorus for Soybean IN Rotation with Brachiaria AS Specie of Covering.

AVAILABILITY OF PHOSPHORUS FOR SOYBEAN IN ROTATION WITH BRACHIARIA AS SPECIE OF COVERING

Moniki Campos Janegitz; Ciro Antonio Rosolem

São Paulo State University, College of Agricultural Sciences, C.P.237, Botucatu,

AL 18603-970, Brazil

Although consider what phosphorus is  a source of finite mineral,  the indroduction a grass crop might be efficient in extraction of fixed P and conversion into forms available to subsequent crops, wich is fundamental component of a sustainable crop rotation system. The objective of this study was to compare capacity of brachiaria (Brachiaria ruziziensis) to recycle phosphorus and increase P availability for the soybean productivity. The experiment was carried out on Lageado Experimental Farm in Botucatu , São Paulo State, Brazil. The experimental was a factorial design of 3 x 3 x 2 with three P treatments, three source, in absence and presence of brachiaria, this treatments were:  consisted of control, soluble and reactive rock phosphate spread over the soil,  where Brachiaria was cropped in sub-plots with  0 and 80 kg ha^-1 of  P₂O₅ aplied by throwing as the cover form. In the soybean planting was added 0, 30 and 60 kg ha^-1  of  P₂O₅ in soluble phosphate form. Soybean was planted over brachiaria in summer (november) after desiccation. Soil samples were taken before soybean  planting and on stadium R6. The P was analyzed in the soil profile until 40 centimeters. Brachiaria, source and doses of P caused effect in soybean productivity. Treatment with 60 kg ha^-1 of P₂O₅, with presence of Brachiaria corresponded to increased production. When brachiaria was not cultivated the highest yield was obtained at a rate of 30 kg ha^-1, corresponding to 77% production. Brachiaria promoted decrease of P available in soils depth observed.

Acknowledgement: FAPESP – PROC 2010/03094-8, CAPES, CNPq