Allelopathic investigations in agroforestry systems are complicated due to lack of conclusive laboratory evidence and, especially, field verification. In agroforestry systems, the allelopathic effects of trees on crops are assessed through laboratory bioassays, pot culture studies and field experiments. Laboratory bioassays include studies to evaluate the effect of aqueous leachate/extract of various parts of trees (leaf, bark, root, leaf litter) on crops. Pot culture studies are done to assess the effect of leachate/extracts of different tree parts on crop growth, to evaluate the effect of different rates of leaf litter or fresh leaf lopping of trees on crops, to study the effect of leaf litter at various stages of decomposition on test crops and to assess the allelopathic effect of tree seedlings on crops through root exudation separating it from competition effects. Field studies are done to study the effect of allelochemicals present in the soil beneath the trees on crops, to assess the effect of tree leaf litter on crops, to separate allelopathic effects of trees from root competition, to determine the effect of field boundary planted trees on crops and to evaluate the effect of leaf litter or leaf lopping of trees applied as mulch or incorporated in the soil on crops and weeds growth. Experimental methodologies to validate the existence and elucidate the role of allelopathy in agroforestry systems are discussed in this paper.
Agroforestry, allelopathy, bioassay, crops, field experiments, germination, growth, methodology, pot culture, trees
