4. Effect of weed management on the growth and yield performances of boro rice cultivars

Abstract

An experiment was conducted at the Agronomy Field Laboratory, Bangladesh Agricultural University, Mymensingh during the period from December 2017 through May 2018 to evaluate the effect of weed management practices on the performance of boro rice cultivars. The experiment consisted of three boro rice cultivars viz., BRRI dhan28, BRRI dhan29 and BRRI dhan74 along with six different weed management practices such as no weeding, application of preemergence herbicide Superhit, application of early post-emergence herbicide Changer, application of pre-emergence herbicide Superhit followed by one hand weeding at 40 DAT (days after transplanting), application of early postemergence herbicide Changer followed by one hand weeding at 40 DAT, and two hand weedings at 20 and 40 DATs. Cultivars had no significant effect on weed density at 20 and 40 DATs but showed significant effect at 60 DAT and weed dry weight was not significantly affected by cultivars at different DATs. Weeding regime had significant effect on weed density and dry weight at different DATs. The highest weed dry weight was observed in no weeding treatment and the lowest one was recorded in application of early postemergence herbicide followed by one hand weeding at 40 DAT. BRRI dhan29 with no weeding treatment produced the highest weed dry weight and BRRI dhan28 with application of early post-emergence herbicide followed by one hand weeding produced the lowest weed dry weight at different DATs. BRRI dhan74 produced the highest grain and straw yields among the studied cultivars. The highest grain yield was obtained from application of pre-emergence herbicide Superhit (Pretilachlor) followed by one hand weeding at 40 DAT due to the highest number of effective tillers hill-1 and highest number of grains panicle-1 in this treatment. Rice cultivar BRRI dhan29 with application of preemergence herbicide followed by one hand weeding at 40 DAT produced the highest grain yield and the lowest one was resulted from BRRI dhan29 in combination with no weeding treatment. From the economic analysis it is observed that cultivar BRRI dhan29 with application of pre-emergence herbicide followed by one hand weeding at 40 DAT maximized the BCR. So, for controlling weeds in effective manner and in order to get the highest grain yield and the highest economic return in boro rice, BRRI dhan29 with application of pre-emergence herbicide followed by one hand weeding at 40 DAT might be recommended.