Management of Gliricidia (Gliricidia sepium) residues for improved sweet corn yield in an ultisol

The nitrogen contribution from Gliricidia (G. sepium) leaves and roots in a Gliricidia alley cropping with sweet corn was quantified by the N-15 isotope dilution technique over 3 cropping seasons. Below-ground competition in the third crop was assessed using P-32 radioisotope. Leaf prunings, roots and their mixture were compared in the presence or absence of hedgerows in a randomized complete block design. The combination of leaf prunings and roots resulted in highest N uptake, plant N concentration, and dry matter yield of corn. The Gliricidia leaf prunings decomposed fast and provided nutrients to the corn crop when applied at 21 and 45 days after planting. By contrast, roots decomposed slowly and did not become an important nutrient source to the corn crop. Belowground competition was observed between hedgerows and corn at 1.7 m distance under conditions of low nutrient availability. However, the competition was masked when the supply of plant available nutrient increased.