Chemical Weeding in Dry Direct Seeding Fields of Single Cropping Middlelate Rice

Chemical weeding in dry direct seeding fields of single cropping middle-late rice was studied in Huida vegetable farm of Huizhou City in 2012. The main treatment was herbicide（ pretilachlor ＋ bensulfuron-methyl,Yangguo and butachlor）,and the sub-treatment was application method（ soil treatments,seedling treatment and integrated treatment）. The results showed that 80 g pretilachlor ＋ bensulfuron-methyl（ 36% pretilachlor ＋ 4% bensulfuron-methyl） diluted with 50 kg water could be sprayed or 200 g Yangguo（ 23. 9% butachlor ＋ 1. 1% bensulfuron-methyl） mixed with 15 kg sandy soil could be broadcasted per 667 m2 on the sowing day or the second day under moist condition of soil,which could effectively control weeds in dry direct seeding fields of single cropping middle-late rice.

Comparison of efficiencies and costs of different weed control methods in paddy production in Iran

Using of efficient and inexpensive method for weed control has an important role in increasing efficiency and reducing costs of production.In this study,field experiments were carried out to evaluate the efficiency and costs of several weed control methods in paddy production during summer in Mazandaran,the north province of Iran in 2011.Seven weed control treatments(T1 to T7)were applied at three stages of rice growth(20 and 35 days after transplanting and grain harvesting time).Weed density,weed dry weight,labor used and economical comparison were determined in the basis of a complete randomized block design with three replications.Results showed that there were no significant differences among efficiencies of six treatments(except for weedy check method(T6)treatment).The minimum weed density and dry weight were obtained at herbicide+hand weeding once(T5)and herbicide application once(T7)treatments during all three stages.The costs of weed control were different among the treatments.Selection of control method has an important role in reducing labor.Hand weeding twice method(T1),because of its high weeding cost,hard work and worker restriction in the required time,is not useful.Powered weeding twice method(T2),due to its zero environment pollution,reducing costs of weed control and high benefit/cost,is the best and most appropriate treatment.Amount of weed damage in weedy check method(T6)varied between 30.5%and 45.3%.

Weed control through allelopathic crop water extracts and S-metolachlor in cotton

Weeds are one of the most important biological constraint to cotton production,and result-ing in a yield losses of up to 90%.The evolution of hundreds of resistant weed species,the lack of new herbicide chemistries,and the increase in weed management costs are all mak-ing weed management more arduous for the growers.Hence,a field experiment was con-ducted to investigate the efficacy of allelopathic crop water extracts(ACWEs)alone and in combinaton with one third rate of S-metolachlor 717g ai.ha-1for effective weed man-agement in cotton.The treatments investigated were;weedy check,sorghum+brassica water extract(WE)at 1.5Lha 1,sorghum+sunflower WE at 1.5Lha-,sorghum+bras-sica+sunflower WE at 1.5Lha-1,sorghum+brassica WE at 15L ha-1+S-metolachlor at 717 g a.i.ha-l,sorghum+sunflower WE at 1.5L ha-1+S-metolachlor at 717 g a.i.ha-1,sor-ghum+brassica WE+sunflower WE at 1.5Lha-1+S-metolachlor at 717 gaiha-,and S-metolachlor at recommended rate of 2.15 kg ai.ha-1.Results revealed that pre-emergent application of sorghum+brassica water extract(WE)at 1.5L ha-1 was the best treatment in terms of effective dry biomass reduction(40%)of Trianthema portulacastrum and Cyperus rotundus,and increase in seed cotton yield(12%).The second best treatment was sorghum+sunflower WE at 1.5Lha-1+S-metolachlor at 717g ai.ha-1 with yield increase of 11%over the weedy control.In comparison,S-metolachlor at recommended rate 2.15kg a.i.ha-1 recorded only 4%decrease in weeds dry biomass reduction and 8%increase in seed cotton yield.Hence,it can be predicted that binary combinaton of sorghum and brassica WE at 1.5 Lha-1 or binary combination of sorghum+sunflower WE at 15Lha-1 with one third dose of S-metolachlor (717g aiha-l)can be used for effective weed management and increase in seed cotton yield.Furthermore,adoption of this technique will also reduce the herbicide application,which is not only benefcial for the ecosystem but,also minimize the evolution of herbicide-resistant weed species.