The objective of this study was to evaluate the shoot phytomass and shrub legumes N, P and K accumulation in agroforestry system (alley cropping system) and study the effect of P fertilization. Two field experiments were carried out - without and with P application - for two years: 2004 and 2005, using shrub legumes in Campos dos Goytacazes - RJ - Brazil. The treatments consisted of alley cropping system with the species: Albizia lebbeck (L.) Benth., Peltophorum dubium (Spreng.) Taub., Leucaena leucocephala (Lam.) R. de Wit., Cajanus cajan (L.) Millsp., Sesbania virgata (Cav.) Pers., Mimosa caesalpiniaefolia Benth.e Gliricidia sepium (Jacq) Pers.. Eight months after the plantation, the legumes were pruned at 1.5-m height, and the shoot phytomass was weighed. Stems with diameter higher than 1.5 cm were not considered in the weighed phytomass. The dry matter obtained in the pruning was expressed as kg ha -1 year -1. Samples from the pruning were used to determine the dry phytomass and N, P and K contents. New pruning was carried out eighty days after the first cut. In the first crop year, Cajanus cajan (L.) Millsp. produced the highest dry phytomass and accumulated the highest amounts of N, P and K; while in the second year, in the experiment with P fertilization, Cajanus cajan (L.) Millsp., Peltophorum dubium (Spreng.) Stend. and Leucaena leucocephala (Lam.) de Wit. produced the highest dry phytomass, and Leucaena accumulated the highest amount of K in shoot phytomass. Phytomass productivity was higher when some legumes received phosphorus application.
Green manure; agroforestry; phosphorus
