Residual Effect of Used Herbicides in Sweet Potatoes on Some Succeeding Vegetables Crops Establishment and Associated Weeds.

Abstract

Little information is known about residual effects of herbicides which use in crop rotations crops and succeeded crops especially vegetable crops grown in these rotations. For this reason two field experiments were conducted in clay soil at EL-Serw Agricultural Research Station, Agricultural Research Center, Damietta Governorate during 2012/13 and 2013/14 winter seasons to study the effect of previous herbicides in non-disturbed soil in experimental plots after harvest of sweet potatoes with removing thrones its and their associated weeds. Herbicides used in the preceding crops during 2012 and 2013 summer seasons being Gesagard 50% SC(prometryn) at 1.0L /faddan, Harness 84% EC(acetochlor) at 1.0L /faddan, Stomp45.5% CS(pendimethalin) at 1.0L /faddan, Sencor 60% SC(metribuzin) at 0.3 L/faddan and added post-emergence herbicides i.e., Select super 12.5%EC(clethodim) at 0.5L /faddan and Fusilade fortey15% EC(fluzifop-p-butyl) at 1.0L /faddan treatments on the establishments of succeeding vegetable crops and weed growth associated in onion, pea, snap beans, cucumber, squash, snake melon and cowpea. The main findings of study show big variation in the residual effects of herbicides which applied in sweet potatoes fields varied from one succeeding vegetable crops establishments to another. For example, onion plant stand at 30 days from sowing can tolerate the residual effects of Gesagard 50% SC + Select super 12.5%EC, Harness 84% EC and Stomp45.5% CS. Squash stand can tolerate the residual effects of Stomp45.5% CS and Harness 84% EC. Cucumber stand can tolerate residual effect of Stomp 45.5% CS, snake melon stand can tolerate the residual effects of Stomp 45.5% CS and Harness 84% EC . Pea can tolerate to somewhat Stomp45.5% CS residues in soil on contrary with both snap beans or cowpea stands had effected drastically and considered very sensitive to residual effects of herbicides in soil previously treated with such herbicides. Concerning the effect of previous herbicides applied in sweet potatoes were poorer with no effects on weeds associated with succeeding vegetable during 2013/2014 season. Thus soils treated in crop rotations with herbicides showed be degraded before growing any succeeding vegetable crops by blowing 2-3 times before planting these crops. Depending on this study more attention towards any determination effects of herbicide residues on environment before herbicide registration by bioassay tests or chemicals.