Identification of the Optimal Lopping Stage of Gliricidia Sepium used as Manure for Coconut Plantations

Abstract

In the light of the current fertilizer crisis in Sri Lanka, there has been a notable increase in the demand for organic fertilizers. Consequently, Gliricidia sepium, a nitrogen-fixing tree, has emerged as a viable option serving as green manure and soil amendment in coconut plantations. However, determining the most appropriate stage for lopping Gliricidia to obtain its optimal nutrient compositions remains uncertain. Therefore, the primary objective of this study is to identify the optimal lopping stage of G. sepium as soil amendment in coconut plantations. The experiment was conducted over three months in an established Gliricidia field, following a Randomized Complete Block Design with three replicates. Plant samples were collected at 4, 6, 8, 10, and 12 weeks after initial cutting, corresponding to different growth stages. The samples were further analyzed to measure various growth parameters and nutrient contents across the lopping stages. The collected data were statistically analyzed using one-way ANOVA at a 5% significance level on Minitab 17 software. The results revealed significant differences (P<0.05) in the mean values of growth metrics and nutrient contents across the lopping stages. As the plant matured, the leaf biomass percentage showed a descending trend while the stem biomass percentage had an ascending pattern. At 10 weeks, leaves displayed the highest nitrogen content (3.43%), thus representing the optimal stage for fulfilling the nitrogen requirements of adult coconut palms, with minimal leaf biomass. These findings have identified the optimal lopping stage of G. sepium to maximize its efficacy as green manure for coconut cultivation. It is recommended that future studies further explore potential positive impacts of utilizing G. sepium as an intercropped green manure, thereby promoting sustainable agricultural practices within the coconut sector.