Acúmulo e decomposição de biomassa de resíduos vegetais de adubos verdes, na recuperação de área degradada no nordeste paraense

Abstract

The management of fallow vegetation is important for maintaining productivity in agroforestry systems in Northeast Pará. During the fallow system there is accumulation of nutrients for subsequent crops. The introduction of leguminous species associated with low soluble phosphate fertilizer can improve the accumulation of biomass and nutrient stocks, therefore enhancing crop yield. Moreover, the process of decomposition of plant residues is important for the study of the release of nutrients such as N and C process, because the leaves of legumes species have low C/N ratio, compared to spontaneous fallow vegetation. Here we compare estimates of biomass, nutrient stocks and decomposition of green manures under different managements of fallow vegetation: 1 spontaneous fallow; 2 enriched fallow with leguminous trees (Racosperma mangium, Cajanus cajan and Inga edulis) and 3 enriched fallow with leguminous trees subjected to phosphorus fertilization of low solubility. The experiment was conducted over 16 months, to analyze the biomass and nutrient stocks, and 150 days to evaluate decomposition and nutrient release of decomposition of N and C, in am degraded arca under chop-and-mulch management of fallow, in the municipality of Igarapé-Acu, Eastern Amazon. The results showed the R. mangium species is most suitable for the enrichment of fallow; phosphorus limits aboveground biomass and N, P and C accumulation of the enriched fallow; the enriched fallow accumulates higher dry mass and nutrient stocks than the spontaneous fallow irrespective of P fertilization; decomposition rates are higher for the enriched fallow species than for the spontaneous fallow species, which may be associated with lower C/N ratio of the enriched fallow species, especially Cajanus cajan.