Assessment of Allelopathy Effects of Agroforestry Trees Leachates on Seed Germination and Growth of Vigna unguiculata L.Walp

Abstract

Agroforestry is an approach to sustainable land management that integrates trees with crops and/or animals. Sensitivity of understory crops to allelochemicals produced by woody perennials required careful evaluation of which species can be effectively incorporated into Vigna unguiculata L models. This study aimed at investigating the allelopathic potentials of Eucalyptus camaldulensis, Albizia lebbeck, and Gmelina arborea on germination and growth behavior of Vigna unguiculata L. Fresh leaves of healthy and mature plants were collected from the mother trees, and were used in the preparation of aqueous extract using distilled water. Germination and growth rate experiments were laid in a completely randomized design (CRD). The germination experiment lasted for 14 days under partial shade while the growth rate was monitored for 45days to examine the effect of the aqueous extract on germination of Vigna unguiculata L. The species leaves extract were tested for the presence of allelochemicals such as phenolic, alkaloid, and flavonoid using standard laboratory techniques.  Findings from this research showed 98% germination for seeds administered with Albizia lebbeck leachates and the control (water), while the least 90% was observed in seeds treated with Eucalyptus camaldulensis leachate.  The highest stimulatory effect (+1.02) was observed in Albizia lebbeck leaf leachates, neutral effect was observed in the control while Eucalyptus camaldulensis leave leachates had inhibitory effect (-7.77) on germination.  Albizia lebbeck proved to be an excellent species that could be incorporated in agroforestry system owing to its stimulatory effect on the test crop. It is recommended that the use of Albizia lebbeck should be encouraged in agroforestry system while Eucalyptus and Gmelina should only be considered for plantation establishment or restoration of the degraded forest landscape.