ALLELOPATHIC EFFECT OF SOME FIELD CROPS ON ASSOCIATED WEEDS

Abstract

Two field experiments were carried out during two successive winter seasons of 2010 and 2011, and two successive summer seasons of 2011and 2012 at the Agricultural Research and Experiment Station, of Faculty of Agriculture, Cairo University, Giza, Egypt. Aims of this study were to: evaluate effects of weed control methods on canola conventional (CT) and zero tillage (ZT) practices and weed control methods on summer crops (maize and soybean) weed parameters and yield components for studied crops. Laboratory experiments were carried during 2013 in Poland, Faculty of Chemistry and second part between weed research lab in Faculty of Agriculture, Cairo University and Central Agricultural of Pesticides Lab., Ministry of Agriculture, Egypt. Canola yield and its components, chemical and mechanical weed control increased seed yield/feddan and reduction fresh weight of weeds/m2 at 55 days after sowing (DAS) in canola plots during both successive winter seasons. Soybean seed yield per feddan increased by hoeing and its interaction with ZT and hoeing weed control on preceding crop increased soybean seed yield per feddan during both seasons and decreased number of weeds/m2 at 55 DAS. On maize the best weed control was provided by the interaction between hoeing under ZT and hoeing on preceding crop during 2010/2011 season. In the second seasons, chemical weed control under CT and hoeing on preceding crop was the best. Chemical weed control under CT and hoeing weed control on preceding crop decreased fresh weight of weeds/ m2 at 55 DAS, but, in general, the interaction between hoeing weed control treatment on maize plots and cultivation under ZT gave the best weed control during both seasons. Certain experiments were conducted under laboratory condition to examine the allelopathic effect of extracts of some crops on germination and seedling parameters of some weed species and crop. Rapeseed and Flax water extracts inhibited the germination % of Avena fatua, Trianthima portulacastrum, Corcorus olitorus, Echinochloa colona.Rapeseed and flax water extracts stimulated the length root of Corcorus olitorus .But, fenugreek extract stimulated the length root of Echinochloa colona.Allelochemicals identified by HPLC in rapeseed extract were benzoic acid, 2,3-hydroxybenzoic acid, vanillic acid and cummaric acid. GC -MS analysis identified certain compounds in flax and fenugreek extracts. Keywords: Allelopathy, maize, soybean, canola, weeds, tillage, herbicides.