Allelopathic influence of rice extracts on phenology of various crops and weeds

In order to study the allelopathic effects of rice straw on different weeds and crops,a lab experiment was conducted at the weed science laboratory,institute of plant environmental protection,national agricultural research center,islamabad during 2007 with a factorial arrangement (species and extract concentration) to evaluate the allelopathic effect of various concentrations of rice straw extract on germination percent,mortality percent,and days to germination of different test plants. the rice plants (basmati super) were collected from experimental fields of national agricultural research center,islamabad. the samples were put into water for 48 hours after getting them cleaned,dried,and ground for obtaining the extract. the rice stems and leaves were used for the extraction and concentrations of 0,50 and 100% rice straw extracts were used for the bioassay. a total of 90 petri dishes were sterilized in autoclave at 110 -120°c for 1 hour. two filter papers were kept in each petri dish and ten seeds of each test plant were placed in each petri dish. all the experimental petri dishes were kept at room temperature of 20°c for 15 days. the results uncovered that 100% rice straw extract convincingly decreased the germination and growth of the test plants,in comparison with the 0 and 50% rice straw extracts. among the crop plants,gossypium hirsutum; and among the weeds,ipomoea batatas,rumex dentatus and convolvulus arvensis were mostly affected by the rice straw extracts whereas helianthus annuus,zea mays,oryza sativa and vigna radiata were somewhat resistant to rice straw extract concentrations. hence,it has been concluded from the results that rice straw can prove to be a good alternative and environment friendly bio-herbicide for weed management in crops.