Decomposição e liberação de nitrogênio de resíduos de Palma de Óleo (Elaeis guineensis Jacq.) em sistemas agroflorestais e monocultivo na Amazônia Oriental.

Abstract

Decomposition is a crucial process for nutrient cycling and carbon storage in ecosystems, but the amount of studies investigating this process in agroforestry systems is still small. The decomposition and release of nitrogen (N) from palm oil residues was evaluated in two agroforestry systems (SAFs) and in a monoculture, both located in northeastern Pará. The residues were classified as empty fruit bunches (CFV), foliole (FOL), rachis (RAQ) and petiole (PEC). During eight months of experiment, the mass loss of residue samples ranged from 80% (FOL e CFV) to 60% (RAQ e PEC) in SAFs to 60% in monoculture, where the fractions present mass loss very similar. Decomposition constants ranged from 2,56 to 1,04 yr -1 in FAS and between 1,35 and 1,15 yr -1 in monoculture. FOL and CFV presented the highest N concentration and the lowest C/N and lignin/N ratio. N concentration and C/N and lignin/N ratios correlated significantly with decomposition rate (r = 0. 964, -0.992 e -0.995, n = 12, P <0.05, respectively). These results suggest that the faster decomposition of FOL and CFV is due to the higher quality of these residues (high N concentration and low C / N and lignin / N ratios). N release in all cultivation systems was also higher by FOL and CFV.