Document Type: Research Paper
Programa de Pós-Graduação em Agroecologia, Universidade Estadual do Maranhão, São Luís, Brazil.
rograma de Pós-Graduação em Agroecologia, Universidade Estadual do Maranhão, São Luís, Brazil.
Programa de Pós-Graduação em Ciência Animal, Centro de Ciências Agrárias e Ambientais, Universidade Federal do Maranhão, Chapadinha, Brazil.
Trees improve the soil quality and their rapid growth in the tropics make
agroforestry systems potentially effective for establishing low-input agricultural
systems in this region. This study assessed the effects of the biophysical
interactions among leguminous trees, weeds, cotton and maize in an alley cropping
system. The experiment comprised six treatments: Clitoria + Gliricidia; Acacia +
Gliricidia; Leucaena + Clitoria; Leucaena + Acacia; Leucaena + Gliricidia and
Control and four replicates in randomised blocks. Cotton and maize were sown
among the legumes. We analysed Ca, Mg, K, P and potential acidity and we
measured the pH using CaCl2 in the soil. Weeds were collected from within a
square 0.5 m on a side in the cotton area. The application of the residues affected
only the levels of Ca and Mg of the soil. The residues did not produce any
differences in the density and richness of the weed species. The sensitivity of some
crops to the allelopathic effects induced by the tree residues is evident mainly in
root growth, in nutrient uptake and in the growth of the shoot. The results presented
here support the view that the criteria for the choice of tree species for agroforestry
systems must go well beyond the potential to enhance soil fertility to obtain the
best results from agroforestry systems.
Keywords: Allelopathy; Cotton; Leguminous residue; Maize; Weed.