Tree-crop interactions in traditional agroforestry systems of Garhwal Himalaya. 1. Phytotoxic effects of farm trees on food crops.
In the traditional agroforestry systems of the Garhwal Himalaya, Uttar Pradesh, fuel, fodder and small timber (multipurpose) trees are cultivated in or around agricultural fields. Some of the tree species used have allelopathic effects on crops so are not grown on a large scale. A comprehensive study of interactions between trees, crops and weeds in these systems is underway, and this paper reports on the toxic activity of the leaves and bark of some major species (Grewia oppositifolia, Ficus roxburghii, Bauhinia variegata, Kydia calycina) on germination and seedling growth of some important food crops (Japanese barnyard millet, Echinochloa frumentacea; finger millet, Eleusine coracana; maize, Zea mays; cowpeas, Vigna unguiculata; soyabeans, Glycine max). In general bark extract of K. calycina and G. oppositifolia significantly reduced germination of all crops, followed by leaf and bark extracts of B. variegata. Radicle growth of all crops except finger millet was suppressed by bark extracts, and leaf extracts reduced radicle growth of all crops. Soyabeans were the most susceptible and barnyard millet most resistant to the toxic action of the tree extracts.