Multipurpose tree species for food , feed and wood : I. Effect of green manure form leguminous species on grain and other yield components of maize.

The study was conducted at the Bako Agricultural Research Center from 1996-1999 with the objective of assessing the effect of incorporation of green manure from legume tree species as a substitute for commercial fertilizers. The treatments tested include incorporation of leaves from different legume tree species (Leucaena pallida, Leucaena diversifolia and Gliricidia sepium), recommended level of N/P2O3 (25/25 kg/ha) applied as a starter fertilizer. In the treatments where the legume leaves were applied, their amount was iso-nitrogenous across all species and incorporated into the soil one month before maize planting and at maize thinning stage. The leaf components used for green manure were sampled initially and analyzed for the chemical entitles. The chemical analysis of the legume plant tissue indicated highest N, lowest acid detergent fiber (ADF), lowest lignin concentration and highest nitrogen to lignin ratio for green manure from Gliricidia seplum. Green manure from Leucaena pallida exhibited higher nitrogen, lower ADF and higher N to lignin ratio than that of Leucaena diversifolia. From the concentrations of N and fiber components, Gliricidia sepium was observed to be a promising green manure legume tree species. The combined analysis of variance over four years for grain and other yield components revealed a highly significant effect of year (P<0.01) on grain yield and stalk dry matter (DM). The effect of treatment was only significant (P<0.01) for leaf DM. The year by treatment interaction effect was not significant (P>0.05) for all residue components, total residue and harvest index but was found to be significant for grain yield (P<0.05). This significant variance ratio of year by treatment interaction for grain yield of maize suggests a difference in the comparative response of maize to different types of fertilizer treatments at different cropping seasons. Thus, the two-way interaction table of year and fertilizer treatments was considered for grain yield. The average effect of years and treatments was separately presented for the other traits. When average over years, higher mean grain yield (94.88 q/ha) was obtained from the plots to which Gliricidia sepium was applied at thinning stage of maize followed by the plots to which the green manure of same tree species was applied at thinning stage of maize followed by the plots to which the green manure of same tree species was applied one month before maize planting. Nearly equal or greater grain yield values were obtained from the plots to which green manure from different leguminous tree species were applied irrespective of the time of application as compared to those which received a recommended level of fertilizer. This implies the possibility of replacing the expensive commercial fertilizers by the locally producible fertility enhancing green manure sources to improve productivity gains from maize based cropping systems. Significant year effect (P =0.05) was observed for stalk yield, total residue and harvest index. For cob, leaf and husk components, no significant effect of year was observed. The mean yield values of total residue DM ranged from 8.08 fro 1997 to 17.15 for 1999. The effect of different fertilizer sources was significant (P=0.01) for leaf, and for total residue and harvest index. No significant treatment effect was observed. Little information has been documented about the potential of Leucaena diversifolia for green manure purposes and other related agronomic aspects. At the same time, Leucaena pallida is also recently been recognized and extensive research information on its utilization has not been well recorded. Nevertheless, the generally higher N and lower lignin concentrations in the leaf component of these tree species and the comparatively higher mean grain yield values achieved in this study suggest these tree species to be the potential legumes for green manure to enhance low external input but internally intensified food crop production systems.