Production, decomposition and half-life of the straw of grass under different levels of manure for no-tillage system in cerrado

Abstract

In the conditions of cerrado (savannah), the climate is favorable in the increase and acceleration of the straw decomposition, thus, hindering the permanence and the maintenance of the residue in the surface of the soil. This work aimed at evaluating the production, decomposition and half-life of straw mixture with grass about the anticipation of levels of the culture successor’s manure in no-tillage system, in the savannah, in the Southwest area of Tocantins. The production of dry mass and the decomposition rate were appraised in an experiment with fifteen types of vegetable covering: millet (Pennisetum americanum), brachiaria (Brachiaria brizantha), forage sorghum (Sorghum vugares pers), bluestem (Gayanus kunth), in single and in mixed plantation, and with 0% and 40% of chemical manure recommended for the culture successor (soy), in savannah soil, in Alvorada, south area of Tocantins. In a Latossolo Vermelho Distrófico, submitted to 13 years of cultivation, which were: 8 years under conventional system with the use of harrow disc and disking; 2 years under minimum cultivation with the use of disking and later subsolador and 3 years under no-tillage system. The obtained results demonstrate that the consortium use of grass increases the straw production in no-tillage system. The increase of the amount of chemical fertilizer promotes increment in the fitomass production, being the most significant effect in the mixed plantation that involved grass. The throwing seeding of the bluestem grass in the soil surface promotes a better exploration of the area which produces straw. However, that grass did not contribute to the increase of the productivity in the mixed plantation to which it was involved. The presence of millet, brachiaria and sorghum grass in mixed plantation increases the production and volume of remaining straw for the system of no-tillage system in both levels of chemical manure.