Nitrogênio e enxofre na adubação e em folhas diagnósticas e raízes do capimbraquiária em degradação

Abstract

It was aimed to study the effects of nitrogen and sulphur combinations on the concentrations of nitrogen and sulphur and on the relationship of nutrients in diagnostic leaves and in degrading roots of signal grass (Brachiaria decumbens Stapf.) before fertilizations. It was collected cylinders with plant+ soil from a degrading pasture in an area of typic Quartzpsamment soil. The experiment was carried out in a greenhouse from November 2003 to March 2004. Five levels of nitrogen (0; 100; 200; 300 and 400 mg/dm3) and five doses of sulfur (0; 10; 20; 30 and 40 mg/dm3) were combined in a study of response surface in a modified central composite experimental design of a fractionated 52 factorial. Three cuts were done in 30-day intervals. The SPAD value in signal grass depends on the combination of nitrogen and sulphur doses only in the first cut; on the second and third cut, there are only the isolated effects of nitrogen doses. The low nitrogen:sulfur ratio observed in the absence of application of nitrogen evidences the higher deficiency of nitrogen than of sulphur in the recovering signal grass. The application of sulphur, and mainly of nitrogen, influences the nutritional status and recovery of signal grass. © 2010 Sociedade Brasileira de Zootecnia.