Allelopathy in Ecological Agriculture and Forestry

The rapidly growing human population has increased the dependence on fossil fuel based agrochemicals such as fertilizers and pesticides to produce the required agricultural and forestry products. This has exerted a great pressure on the non- renewable fossil fuel resources, which cannot last indefinitely. Besides, indiscriminate use ofpesticides for pests (weeds, insects, nematodes, pathogens) control has resulted in serious ecological and environmental problems viz., (A) Increasing incidence of resistance in pest organisms to important pesticides. (B) Shift in pests population, particulary in weeds and insects. In weeds, species that are more closely related to the crops they infest have developed. In insects, scenario is most grim, the predators have been killed and minor insect pests have become major pests and require very heavy doses ofhighly toxic insecticides for their control. (C) Greater environmental pollution and health hazards (a) particularly from contamination of surface and underground drinking water resources and (b) from their inhalation during handling and application. (D) Toxic residues of pesticides pollute the environment and may prove hazardous to even our future generations. (E) Some agricultural commodities may contain minute quantities ofpesticides residues, with long tenn adverse effects on human and livestock health. Therefore, serious ecological questions about the reliance on pesticides for pests control has been raised. The use of fertilizers, besides causing environmental problems has also impoverished the soil health and decreased the beneficial soil fauna. For example, in some major crop rotations viz.