Viabilidade agroeconômica da integração lavoura-pecuária na recuperação de área de pastagem degradada com fosfato arad na Amazônia oriental.

Abstract

The pasture implementation in Amazon has replaced the forest by using the slash and burn process within soil characterized as poor in mineral in special phosphorous. The lack of pasture management, decline of available phosphorous from the ashes and the reduction of biomass provoke pasture and soil debilitation in one or more decades. As a result, these areas are abandoning so that the farmer repeat the same process in a different area raising the deforestation. To recovery these areas is not only necessary but also could contribute to the reduction of deforestation in this Region; the integration of crop fields with pasture can be used to this end. The aim of the work was to evaluate the action of different combinations of fertilizer using corn (Zea mays,L), cowpea beams (Vigna unguiculata, Walp) and braquiarão (Brachiaria brizantha) in a integrated system for the recovery of depredated pasture. This study was installed in Santo Antônio do Tauá county, in Para State, in a depredated pasture over an yellow latosol of Para State. The experimental sampling used was randomized complete blocks with parcels subdivided with four repetitions. In each parcel were used four proportion of phosphorous: 50; 100, 200 and 300 kg ha-1 of P2O5, in the form of Arad´s phosphate, combined with NPK (111 kg ha-1 de urea + 130 kg ha-1 of triple superphosphate + 84 kg ha-1 of potassium chlorate), NK (111 kg ha-1 de urea + 84 kg ha-1 of potassium chlorate), NK + liming (111 kg ha-1 de urea + 84 kg ha-1 of potassium chlorate + liming) and a blank sub parcel. The first specie to be planted and fertilized was corn followed by cowpea bean in consortium with braquiarão. Within this study were assessed components of productivity of corn and cowpea bean, the availability of fodder and the rate of growth of braquiarão. The different amounts of Arad did not provoke significant changes in productivity components of corn, however the use of it combined with soluble phosphates enhanced this productivity and other attributes of corn, overcome the other combinations of fertilizers. The growth and productivity of corn were very damaged within the combinations of fertilizers that did not receive soluble phosphate. There were no difference amongst the use of Arad phosphate in terms of productivity of corn; however cowpea bean´s productivity was superior to the national and regional average due to the effect of the fertilizers residual effect. The higher production of cowpea bean was achieved when was used Arad+NK+limestone and Arad+NK. This indicate that residual effect of Arad was enough to supply phosphorous to them. The different amounts of Arad did not provoke significant changes in the availability of fodder neither in the growth rate of braquiarão. All different amounts of Arad used without the combination with limestone showed to be economically feasible, on the other hand the use of limestone in all situations was not economically feasible.