Effect of use of savanna tree leaves as mulch materials on germination and growth of selected annual crop seedlings

Abstract

Leaves of indigenous and exotic tree species adapted to the climatic conditions of the northern Guinea savanna of West Africa were evaluated for use as a mulch material and screened for their effect on germination and early growth of two varieties each of soybean (Glycine max), cowpea (Vigna unguiculata), maize (Zea ways), sorghum (Sorghum bicolor) and millet (Pennisetum glaucum). Seed germination, and radicle and shoot fresh weight were examined after 7 days of incubation in petri dishes with aqueous extracts of dried ground tree leaves. Aboveground dry matter content and weed numbers were observed in a pot study in which dried ground tree leaves were mixed with the top 3cm layer of soil. The most consistent negative effects across both trials and all crops were observed in the Erythrophleum suaveolense and Combretum molle treatments. Vitellaria paradoxum, Prosopis africana and Entada africana induced adverse effects in the petri dish test but not in potted soil. Tamarindus indica also induced negative effects on germination and radicle growth in petri dishes but stimulated early crop growth in the pot study. Based on these studies E. suaveolense, C. molle, and Daniellia oliveri should not be used as mulch materials in the development of agroforestry systems utilizing MPTs (Multi Purpose Trees). On the other hand, the beneficial effect of the use of T. indica, Ficus polita and Piliostigma reticulatum should be confirmed. Since the in vitro screening method applied is rapid but some discrepancies in the results were observed, it should be complemented by pot screening.