Evaluation of Gliricidia sepium provenances in an alley cropping system with maize in Sri Lanka using vector competition analysis

The productivity of an alley cropping system comparing three provenances of Gliricidia sepium, originating from Sri Lanka and each of the wet and dry zones of Guatemala was evaluated in sole and mixed crop combinations in the intermediate zone of Sri Lanka. The objectives were to investigate growth and nutrient interactions in the alley cropping system of G. sepium provenances with maize using Vector Competition Analysis (VCA), and recommend the most effective G. sepium provenance to improve crop productivity and soil fertility. Yield measurements revealed that the growth interactions were synergistic except in alleys with the dry provenance of Guatemala. Both crop and tree yields exceeded sole cropping yields, and the major limiting factors of productivity were identified as nutrients, particularly nitrogen on VCA. The wet provenance of Guatemala was recommended for use because of its superiority in biomass production and soil fertility enrichment, and low underground competition.