BIOMASS AND NUTRIENT ACCUMULATION OF TWO LEGUMINOUS TREES IN AN IMPROVED FALLOW IN AMAZON RAIN FOREST

A vegeta\ue7\ue3o de pousio \ue9 um dos principais componentes dos sistemas agroflorestais sequenciais de derrubada e queima, praticados tradicionalmente pela agricultura familiar na Amaz\uf4nia. A remo\ue7\ue3o progressiva de nutrientes do solo por essa pr\ue1tica implica redu\ue7\uf5es cont\uednuas nos estoques de carbono e nutrientes causando decl\uednio da produtividade do solo, perda da capacidade de regenera\ue7\ue3o e diminui\ue7\ue3o da diversidade de esp\ue9cies da vegeta\ue7\ue3o. O melhoramento de pousio com esp\ue9cies leguminosas fixadoras do nitrog\ueanio atmosf\ue9rico pode contribuir para uma maior produ\ue7\ue3o de biomassa e ac\ufamulo de nutrientes em compara\ue7\ue3o com a vegeta\ue7\ue3o espont\ue2nea, atendendo \ue0 demanda nutricional das culturas subsequentes, podendo ser considerada como uma tecnologia de produ\ue7\ue3o sustent\ue1vel. Esse trabalho avaliou o efeito da aduba\ue7\ue3o fosfatada de baixa solubilidade no ac\ufamulo de biomassa e nutrientes da parte a\ue9rea de leguminosas arb\uf3reas utilizadas em melhoramento de vegeta\ue7\ue3o de pousio. O experimento foi conduzido por 23 meses, em um sistema agroflorestal de \u201ccorte e tritura\ue7\ue3o\u201d em Marapanim, Par\ue1. Foram utilizadas as esp\ue9cies tachi-branco - Sclerolobium paniculatum Vogel e ing\ue1 - Inga edulis Mart e foram estimados biomassa, teor e estoque de nutrientes dos compartimentos folha, galho e tronco. Houve ac\ufamulo de biomassa, estoques de P, Ca e Mg nas folhas, estoque de P nos galhos e o teor de c\ue1lcio nas folhas das leguminosas \ue9 limitado por f\uf3sforo, segundo os resultados encontrados. A esp\ue9cie Inga edulis apresentou maiores teores de pot\ue1ssio, c\ue1lcio e magn\ue9sio nos compartimentos folha, galho e tronco, enquanto que a esp\ue9cie Sclerolobium paniculatum apresentou maiores ac\ufamulos de biomassa e estoques de nitrog\ueanio, f\uf3sforo, pot\ue1ssio, c\ue1lcio e magn\ue9sio nos compartimentos folha, galho e tronco.The fallow vegetation is the main component of sequential agroforestry systems in Amazon rain forest.The progressive removal of soil nutrient by slash/mulch agriculture involves continuing losses in carbon and nutrient stocks, leading to decline in soil productivity, low regeneration ability and decrease of species diversity of fallow vegetation. The fallow vegetation management by introducing fast growing leguminous trees has the potential to accumulate more biomass and nutrients to serve the nutrient demands of crops and its management has been considered as a sustainable technology production. This study aimed to evaluate the effect of low solubility of phosphorus fertilizer in the biomass and nutrient stocks of leguminous trees used in fallow improvement. The experiment was conducted for 23 months in a sequential agroforestry slash-and-mulch system in eastern Amazon forest. The species selected were tachi-branco - Sclerolobium paniculatum Vogel and inga - Inga edulis Mart. Biomass and nutrient stocks and nutrient concentrations of leaf, branch and trunk were estimated. Phosphorus fertilization had a positive effect on calcium concentration in the leaves and stocks of biomass and nutrient contents (phosphorus, calcium and magnesium) in the leaves of legume trees. Inga edulis showed higher levels of potassium, calcium and magnesium concentrations in leaves, while Sclerolobium paniculatuttm showed higher biomass and stocks of nitrogen, phosphorus, potassium, calcium and magnesium in leaf, branch and trunk