Crescimento, acúmulo de nutrientes e fixação biológica de nitrogênio de flemingia macrophylla

Abstract

Flemingia macrophylla is an Asian shrub legume scarcely known in Brazil. The objective of this work was to evaluate the growth, nutrient accumulation and biological N2 fixation of flemingia. Two field experiments were conducted from December 2006 to December 2007, in Seropédica and in Avelar, Rio de Janeiro State. Both experiments were arranged in a completely randomized block design with four repetitions, and the treatments consisted of the different sampling times. Leaf area, biomass and nutrient accumulation in leaves and branches were measured in twelve monthly samplings. Biological N2 fixation was estimated by the natural abundance of 15N. Shoot biomass yield reached 4.0 Mg ha-1 in Seropédica and 2.3 Mg ha1 in Avelar at 360 days after transplanting (DAT). The lower growth in Avelar was associated with the colder and drier winter than in Seropédica. The highest crop growth rate was observed at 165 DAT, Vermeat the first flowering. Accumulation of N, P, K, Ca and Mg in shoots was, respectively, 74, 5, 33, 25 and 8 kg ha-1 at 360 DAT. The percentage of N derived from biological N2 fixation was approximately 76% which provided 57 kg ha-1 of N originated from symbiosis in shoots at 360 DAT. The results indicate that flemingia may provide significant amounts of biomass and nutrients, especially N, arising as a promising species to be introduced as green manure and alley cropping in agricultural systems.