BIOMASS DECOMPOSITION AND NUTRIENT RELEASE OF BRACHIARIA AND GUINEA GRASS UNDER BRAZILIAN SAVANNAH CONDITIONS

The objective of this research was to evaluate the accumulation and release of nutrients from the dry biomass of brachiaria (Brachiaria brizantha) and guinea grass (Panicum maximum) used as cover crops in a no-tillage system, under Brazilian savannah conditions. The experiment was carried out at Embrapa Arroz e Feijão (Fazenda Capivara), in Santo Antônio de Goiás, Goiás State, Brazil, in a dystrophic Red Oxisol. A randomized block design, with four repetitions, in a split plot scheme in time, was adopted. At the flowering stage, plants were cut and kept on the soil, and the productivity of dry biomass, and nutrient accumulation, decomposition and liberation were evaluated at 0, 15, 30, 45, 60, and 75 days. The biomass yield was 16,643 kg ha-1, for brachiaria, and 18,244 kg ha-1, for guinea grass. For both cover crops, N was the most accumulated nutrient. Among the macronutrients, K showed the highest release rate (70% and 59%, respectively for guinea grass and brachiaria). KEY-WORDS: Brachiaria brizantha; Panicum maximum; decomposition rate; macronutrients accumulation; no-tillage system.