Inhibition of plant residues may release secondary metabolites that can favourably or adversely affects other plants. The overall objective of these study is to determine whether the leaf extract and decomposition products of leaf mulch of Acacia auriculiformis, Eucalyptus citriodora and Gliricidia sepium contain allelochemicals that are inhibitory to the physiology of millet (Panicum miliaceum L.). In a pot experiment, application of leaf extract depressed the dry weight of millet seedlings relative to the control with the observed phytotoxic interference not increasing with extract concentration except for Eucalyptus and Gliricidia extracts. The results also showed that in terms of duration, the inhibitory effect waned with time and was more pronounced at two weeks after application than at six weeks. It is evident from the results that the severity and persistence of the inhibitory effect of the extracts was in the order: Gliricidia > Eucalyptus > Acacia. The results of pot experiment also showed that there were difference between extract and mulch in their inhibitory effects as phytotoxic interference occurred earlier in pots that received extract solution compared to mulched pots. In contrast to results obtained when extracts were added, high rates of mulch application did not interfere to reduce dry weight but increased it relative to control. The present results demonstrate appreciable and varying degree of phytotoxity exhibited by the mulch species of millet plant through inhibition of its physiological processes such as seed germination, chlorophyll formation and growth. Keywords: Inhibition, Tree species, Physiology and Millet Plan
