ALLELOPATHIC ACTIVITIES OF N-HEXANE AND ETHYL ACETATE EXTRACT OF AZADIRACHTA INDICA ON THE GERMINATION OF MAIZE SEEDS

ABSTRACT The alarming rate of residual toxicities of several herbicides and insecticides in agricultural produce calls for urgent attention. Azadirachta indica leaf is one of the natural insecticides that is generally used on various crops at various stages. Many of these natural insecticides have positive or negative effects on plant growth. Therefore, this study determined the qualitative phytochemical constituents and the allelopathic effects of Azadirachta indica leaf extract on Maize seed germination and seedling growth using standard method. Hence, the allelopathic effects of N-hexane extracts of A. indica leaf was determined on maize seed using concentration of 2.5%, 5.0% and 10% for 12 days. On days 3, 6, 9 and 12, the root and shoot development, germination percentage, and seedling vigour of maize seeds were determined. Both N-hexane and ethyl acetate extracts contained B-Caryophyllene, Trans-B-Farnes, Alpha lonone, Phytol, Myricetin, Quarcetin, Azadirachtol, Azadirachnol, Azadirachta A, Phyllene and Ascaridol. The inhibition of plumule and radicle growth were observed to be concentration-dependent with the highest percentage of inhibition in 10% of n-hexane extract of Azadirachta indica. Germination percentage also decreased with higher concentration, with a maximum of 100% germination in the control group, and only 10% and 30% at 10% and 5% concentrations respectively. Similarly, Seedling vigour index was drastically reduced at higher concentrations, with a value of 3.6 and 37.8 at 10% and 5% respectively, as compared to 423 in the control group. These findings suggests that high concentration of A. indica (10% and 5%) extract inhibit maize germination and seedling growth. Therefore, high concentrations should be avoided when using A. indica leaf extract as insecticide during germination stage of maize.