Allelopathic interactions in soil

The soil is the site of most biochemical reactions and interactions affecting the plant growth. It serves as a medium for the diffusion of substances released by plants and to keep other plants away from growing too close to them. Such substances are called allelochemicals and are released in the soil through root exudation, leaching, volatilisation, biomass decay, etc. These chemicals affects various processes such as germination of seeds, nitrogen fixation, mineralisation, etc. The bioactivities of the allelochemicals are controlled by soil properties (pH, solute concentration, cation exchange capacity, fertility) and also by cultural practices such as tillage and crop rotations. The principles of allelopathy can be effectively exploited to improve soil fertility (e.g. green manuring in soil) or improve nitrogen use efficiency by plants (e.g. incorporation of neem and other plant materials for reducing nitrification rate). Similarly, certain plant materials have beneficial effects on the soil micro- and macro-fauna, which in turn influences the fertility of the soil. This paper deals with some plants and soil organisms releasing allelochemicals in the soil and the interaction of these chemicals with the soil.