Effects of Legumes Tree Leaf Mulch Placement and N-Mineralization on Maize Productivity in a Tropical Rainforest Area

Nutrient depletion in the rainforest area is a land use constraint that needs urgent attention. This study was carried out to investigate the effects of legumes tree leaf mulch placement and N-mineralization on maize productivity in a rain forest area. Three common indigenous nitrogen-fixing leguminous trees (Albizia ferruginea, Albizia zygia and Spondias mombin) were randomly selected around the experimental site. Fifty (50g) of freshly collected leaves from these species were bulked and weighed into 20cm x 25cm litter bags. Three litter bags were placed above-ground and three below-ground (5cm deep) at three replicates per treatment. Maize was planted at a spacing of 90cm x 30cm. Fresh samples of each mulch were applied in a ring form to the three selected plant per plot in above-ground and below-ground (5cm deep) pattern two weeks after planting. The results showed that Albizia ferruginea had the highest percentage nitrogen (5.49%) and Spondias mombin had the lowest (3.49%). The percentage calcium composition of Albizia ferruginea and Albizia zygia was the same order of magnitude (0.22%), while that of Spondias mombin was 0.16%. The decomposition rate of the samples was highest in Spondias mombin with the lowest remaining weight of 2.92g and 3.16g in above and below ground litter bags respectively at week 10. Albizia ferruginea leaf had the highest nitrogen mineralization of 61.59% at above ground placement and Spondias mombin had the lowest of 52.18%. Nitrogen mineralization in the below ground placement was highest in Spondias mombin (67.32%) and lowest in Albizia zygia (40.39%). Generally, the above ground mulch placement decomposed faster than the below ground mulch placement at week 10. Albizia zygia was found to have outstanding performance on the height, girth and yield of maize. It is therefore recommended to poor resource farmers to allow Albizia zygia to thrive in and around their farms so that the leaves could be used as mulch for crop production