Nitrogen Use Efficiency in an Agrisilviculture System with Gliricidia sepium in the Cerrado Region

Gliricidia (Gliricidia sepium) is a tree legume that has great potential for use in agriculture because of its multiple-use characteristics. However, there is little information in the literature about the effect of agrisilvicultural systems on nitrogen (N) cycling. This study evaluated the effect of densities of gliricidia on N cycling under an agrisilvicultural system. The treatments were composed of different densities of gliricidia: 667, 1000 and 1333 plants ha^-1, with a fixed spacing of 5 m between the alleys. The efficiency of N use was investigated by using the ¹⁵N isotope tracer. In each plot, a transect perpendicular to the tree rows was established in two positions: (i) in the corn (Zea mays) row adjacent to the trees, and (ii) in the corn row in the center of the alley. The N fertilizer recovery efficiency ranged from 39% in the density of 667 plants ha^-1 to 89% with 1000 plants ha^-1. The effect of gliricidia on the N uptake by corn was higher in the central position of the alley with 1000 plants ha^-1. The agrisilvicultural system with 1000 plants ha^-1 was highly efficient in the recovery of mineral N, representing an excellent option for integrated production systems in tropical regions.