Biomass allocation and nodulation of Gliricidia sepium under two cut-and-carry forage production regimes

The effects of two pruning regimes on the above-ground biomass allocation and nodulation of Gliricidia sepium (Jacq.) Walp. (Leguminosae: Robinieae) were studied in a cut-and-carry forage production system under humid tropical conditions in Guadeloupe, French Antilles. The grass layer composed of a mixture dominated by Paspalum notatum Flügge (80%) and Digitaria decumbens Stent. The pruning regimes were partial pruning (ca. 50%) every two months and complete pruning every six months. The complete pruning caused an almost complete turnover of N2 fixing nodules. The nodule biomass decreased after the partial pruning, but the turnover was not complete. The nodule to foliage biomass ratio followed the same pattern under both treatments, and the values of the ratio converged towards the end of the experimental period. The maxima of standing nodule biomass were 7.2 and 13.0 kg ha−1 in the partially and completely pruned trees, respectively. The cumulative leaf fodder harvest was higher under partial pruning management, due to smaller litter loss. The branch biomass production was higher under complete pruning management. Grass production was not affected by the pruning pattern of G. sepium. It was concluded that the partial pruning management produces more fodder in the studied association, and the nodulation probably adjusts to the canopy N requirements. The potential N release to soil in the turnover of nodules of G. sepium (max. 0.82 kg ha−1) is negligible compared to the N export in tree and grass fodder harvest, 190 and 215 kg ha−1 in partially and completely pruned plots, respectively. This revised version was published online in June 2006 with corrections to the Cover Date.