Allelopathic effect of various plant leaf extracts on weed control in cotton

Allelopathy may help in weed control through inhibition of weed seed germination and weed seedling growth. The allelochemicals present in the plant species may be used to develop newer bioherbicide to combat the evolution of herbicide resistance in weeds. Cotton being a long duration and wide spaced crop having the habit of growing at slower rate in early stages and much of vacant interspaces remain unutilized. Hence, weeds take the advantage of soil moisture, and soil fertility to suppress the crop growth. Based on the concept, this experiment was conducted at the Agricultural College and Research Institute, Madurai during 2012. For the experiment, fresh leaves of plant species Annona squamosa, Azadirachta indica, Calotropis gigantea, Leuceana leucocephala, Eucalyptus camaldulensis, Vitex negundo were collected from the plants found in nearby places of Madurai. The fresh leaves of the above species were collected and soaked in alcohol and water at 1:1 proportion and kept overnight. After 12 h, the leaf extract for each of the above species were prepared by filtration, which is 100% stock solution. From the stock solution, 10, 20 and 30% concentration were prepared and sprayed as pre-emergence application. Among the six plant species, pre-emergence application of Calotropis gigantea at 30% (T₁₀), Calotropis gigantea at 20% (T₉) and Calotropis gigantea at 10% (T₈) recorded lesser weed density, dry weight and higher weed control efficiency compared to other leaf extract sprays.