Journal of crop and weed 2(1): 1-4 (2006) Effect of weed management practices on yield and economics of rainfed transplanted rice L. N. SINGH, A. I. SINGH AND A. K. KUMAR SINGH Department of Agronomy. Cehtral Agricultural University, Imphal ABSTRACT Collection and identification of major predominant weeds were done from the low land rainfed rice fields of Manipur. Out. of the different species, 12 weed species were identified as predominant, constitutihg 90% of the weed population. Regarding their control measures, two pre-emergence weedicides (Butachlor and Oxyflurofen) with and without a post- emergence weedicide (2, 4-D) and mechanical paddy weeder were tried and compared with hand weeding. Among the different treatments, Butachlor (1 kg a.i./ha) + 2, 4-D (0.75 kg a.i./ha) +paddy weeder was found equally good as that of two hand weeding with regards to yield but economically more profitable. Key word: Predominant weeds, Butachlor, Oxyflurofen, 2, 4-D and Mechanical weeding. INTRODUCTION Rice being a rainy season crop and its growing season also being congenial for growth of many weeds often leading to heavy weed competition and yield reduction even upto 98% (Mani et al., 1986). Even though chemical weed control is pref erable from economic point of view, reports on environmental unsaftiness are coming up due to wrong selection of the chemical as well as overdose. On the other hand, hand weeding is also uneconomic and unapplicable in areas where there is labour scarcity. Thus it is e\i.dent that no single mediod of weed control offurs oompleres solution to all problems and fur all the situations. Hence, in order to minimise various problems and for increasing herbi cide efficacy combination of two or more methods so as to call integrated approach is the theme of the present research. MATERIALS AND METHODS A field experiment was carried 0ut at the Research Farm of College of agriculture, CAU, Imphal during kharif of 1994, 1995 and 1996. The soil of the experimental site is clay and acidic (pH 5.4). The crop (cv. K.D. 2 _ 6 _ 3 ) was transplanted in July at 30 x 10 cm spacing and harvested in November as rainfed crop in all the years. A nutrient dose of 60 kg N, 40 kg Pp 5 and 30 kg K 2 0 per hectare was applied. There were 12 different trea tments (Table 2) and which were replicated thr ee times m randomised block design. Yield contributing characters like number of effective tillers per spuare metre, number of filled grains per panicle and grain yield were recorded at the time of harvesting and threshing. Besides the weed population and weed dry matter were recorded at 70 DAT. Economics of the different treatments over control was also calculated. RESULTS AN D DISCUSSION Weed flora collected indicated that 12 spp. Of weeds (Table 1) constituted about 90% of the total weed population. Effect on weed dry weight : Data presented in Table 2 on dry weight of weeds revealed that all the weed control treatments reduced the weed dry weight significantly from that ofunweeded treatment in all the three years of experimentation. The lowest weed dry weight (21.7 - 25 .5 g/m 2 ) was recorded in tw hand weeding treatment while the highest value of (176.0-190.1 g/m 2 ) was observed in unweeded treatment. But the treatments like Oxyflurofen (pre) +One hand weeding (50 DAT) and Butachlor (Pre) + 2, 4 -D (Post)+ Paddy weeder also gave better result in comparison to that of remaining treatments . Similar results were also reported by Samantaray et al. (2000). Effect on yield Perusal of the Table 2 further revealed that even though slightly higher number of effective tillers was observed in two hand weeding treatment, it was found statistically insignificant from other weed