Soil applied herbicide influence on weed growth and performance of transplant aman rice varieties

Weed causes huge yield losses in rice if not managed properly. The most effective and economic way to control weed is application of herbicide and therefore it is important to study the effect of herbicides on weed suppression and yield performance of rice. The research work was conducted at the Agronomy Field Laboratory, Bangladesh Agricultural University, Mymensingh during the period from June to December 2014. Experimental treatments included three aman rice varieties i.e. Nizershail, Bashiraj and BRRI dhan52, and six different weeding regimes such as no weeding, soil applied herbicide Polyfit (pretilachlor) 500EC at 6 days before transplanting, at 3 days before transplanting, at the same day of transplanting, at 3 days after transplanting and at 6 days after transplanting. The experiment was laid out in a randomized complete block design with three replications. Nine weed species belonging to five families infested the experimental plots. Weed population and weed dry weight were significantly affected by rice variety and weeding regime. The maximum weed growth was noticed with local varieties Nizershail and Bashiraj and the minimum one with high yielding variety BRRI dhan52. Rice variety BRRI dhan52 produced the highest grain and straw yields. The highest number of effective tillers hill-1, number of grains panicle-1, 1000-grain weight were observed when Polyfit 500EC was applied in soil at 6 days after transplanting (DAT). Application of Polyfit 500EC in soil at 6 DAT was the most effective treatment in controlling weeds and also in producing grain yield of rice. High yielding rice variety is not only more productive but also more weed competitive than local variety. Weed infestation results in significant yield losses of rice if not managed properly. For better weed management and higher yield of aman rice, application of Polyfit 500EC (Pretilachlor) at 6 days after transplanting might be recommended.