Allelopathic effects of tree species on crops in Eastern Himalaya, India

In Laboratory bioassays and pot cultures, the allelopathic influence of leaf extracts of Aquilaria malaccensis Lam. (Syn. A. agallocha Roxb.), Michelia champaca Linn., Tectona grandis Linn. and Trema orientalis Blume were studied on crops [Cereals: Oryza sativa Linn. (cv. Ranjit) and Zea mays Linn. (cv. Vijay Composite); Legumes: Vigna radiata Linn. (cv. SG-1) and Vigna umbellata Thunb. (cv. Naga Local) and Oilseeds: Arachis hypogeae Linn. (cv. ICGS 76) and Brassica campestris Linn. (cv. TS-38)]. The leaf extracts significantly (P < 0.05) reduced the germination, growth and dry matter in both bioassay and pot culture. Irrespective of tree spp. and test crops, germination, root-shoot length and dry matter yields were reduced by 11.0, 21.5 and 25.3% respectively. All the test crops were found sensitive to allelopathic influences of tree spp., particularly of M. champaca and T. grandis. Phytotoxic responses of A. malaccensis and T. orientalis were species specific. The legume test crops were most sensitive to toxic accumulation of tree spp., followed by cereals (O. sativa, Z. mays) and B. campestris.