Effect of weed-management practices on nutrient depletion by weeds, yield and economics of winter-irrigated cotton (Gossypium hirsutum)

A field experiment was conducted on sandy-loam soils during winter seasons of 2001–02 and 2002–03 at Bhubaneshwar, to explore effective weed management in irrigated cotton. Eleusine indica L. Dactyloctenium aegyptium (L.) Beauv., Digitaria sanguinalis L., Cynodon dactylon L. Pers. Cyperus rotundus L., Cyperus iria L., Ageratum conyzoides L., Heliotropium indicum L. and Gnaphalum indicum L. were the major weed flora in the unweeded control plot. Post-emergence directed spray of paraquat dichloride @ 0.2 kg/ha at 30 days after sowing with follow up hand-weeding at 60 days after sowing recorded the lowest weed population, maximum weed-control efficiency, highest plant height, leaf-area index, number of sympodia, bolls/plant and boll weight, and significantly increased seed-cotton yield, net return, benefit: cost ratio with maximum NPK uptake compared to other weed control and unweeded control due to lesser weed competition. It was followed by pre-emergence spray of alachlor @ 1.0 kg/ha at 3 days after sowing with a hand-weeding at 40 days after sowing, Weeds if not controlled within 60 days after sowing, could deplete NPK to the extent of 87.1, 17.9 and 61.7 kg/ha at 90 days after sowing.