Among the food crops, rice is the mainstay of the sustenance of Asia’s population since long. Therefore, smart rice research is needed to make the rice production systems economically and ecologically sustainable. Weeds are known to be a major biotic constraint in agricultural production systems. Of the total annual loss of agricultural produce from various pests in India, weeds accounts for 45%, insect 30%, diseases 20% and other pests 5% (Rao, 1983). In India, yield loss due to weeds in transplanted rice was estimated to the tune of 30.9 % over weedy check (AICRP-weed management, 2003-2012). Considering the diversity and complexity of weed problem, it can be stated that no single method of weed control whether cultural, manual, mechanical or chemical would be sufficient to provide season-long sustainable weed management under transplanted rice ecosystem. In the above-mentioned perspective, a field experiment on weed management in ‘Mashuri’ cultivar of rice was carried out at Uttar Banga Krishi Viswavidyalaya, Pundibari, Cooch Behar, West Bengal during kharif season of 2016. The experiment was laid out in randomized block design having 12 treatments replicated thrice: T₁ – Weedy check; T₂ – Weed free; T₃ – PW at 15, 30 and 45 DAT; T₄ – Metsulfuron methyl 20% WP @ 8 g a.i. ha^-1 at 10 DAT; T₅ – Bispyribac sodium 10% SC @ 20 g a.i. ha^-1 at 14 DAT; T₆ – Bispyribac sodium 10% SC @ 30 g a.i. ha^-1 at 14 DAT; T₇ – Pretilachlor 0.60 kg a.i. ha^-1 + PW at 25 and 40 DAT; T₈ – Pretilachlor 0.60 kg a.i. ha^-1 + 2,4-D 0.50 kg a.i. ha^-1 at 30 DAT + PW at 45 DAT; T₉ – Pretilachlor 0.60 kg a.i. ha^-1 + Bispyribac sodium 10% SC @ 20 g a.i. ha^-1 at 22-25 DAT + PW at 40 DAT; T₁₀ – Bispyribac sodium 10% SC @ 20 g a.i. ha^-1 at 20 DAT + PW at 40 DAT; T₁₁ – 2,4-D 0.50 kg a.i. ha^-1 at 25 DAT + PW at 40 DAT and T₁₂ – Pretilachlor 0.60 kg a.i. ha^-1 + Metsulfuron methyl 20% WP @ 8 g a.i. ha^-1 at 10 DAT. It was evident from the results that almost all the growth and yield attributes, weed population (no m^-2), dry weight of weeds (g m^-2), WCE, WCI and WI differed significantly with different weed management practices. So far as growth components and yield attributes were concerned, T₂ i.e. weed free exhibited the best performance closely followed and in some cases being at par with T_9. Highest grain yield (4.23 t ha^-1) was achieved from weed free being at par with T₉ (4.14 t ha^-1) but differed significantly from others. Apart from weed free treatment, highest WCE & WCI was achieved from T₉. Excepting T₂ lowest weed index at harvest (1.72 %) was also achieved from T₉. As far as the production economics was concerned, highest gross return (Rs. 68541.00/ha) was obtained from T₂ followed by T₉ (Rs. 67198.00/ha). But in case of net return, highest value of Rs. 29223.00 was obtained from T₉ and due to its high cost of cultivation T₆ showed highest input: output ratio (1:1.80) narrowly followed by T₉ (1:1.77). So, it was concluded that the treatment T₆ or T₉ could be opted for sufficient control of weeds in transplanted kharif paddy in terai zone of West Bengal to maximize the economic return.

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