Effect of application of post-emergence herbicides at different levels of available soil moisture content in irrigated wheat (Triticum aestivum)

A field experiment was conducted during the winter ( rabi) season of 200809 and 200910 at Jabalpur, Madhya Pradesh, to study the effect of post emergence herbicides (isoproturon @ 0.75 kg/ha, clodinafop @ 0.06 kg/ha and clodinafop followed by 2,4-D @ 0.5 kg/ha) against weeds under different available soil-moisture regimes (ASM) (100%, 95%, 90%, 85% and 80%) on weeds, nutrient depletion by weeds and uptake by crop and the grain yield and economics of wheat [ Triticum aestivum (L.) emend. Fiori & Paol]. Herbicidal application at 100% available soil moisture resulted in significantly lowest weed density and total dry weight of weeds during both the years and hence lowered the nutrient depletion by weeds and increased the uptake by the crop. The presence of 100% available soil moisture registered significantly higher grain yield of wheat (6.1 t/ha) and proved significantly supe- rior to 85 and 80% ASM. Post-emergence application of clodinafop followed by 2,4-D caused significantly lowest total weed density (7.8/m2) and dry weight (5.1 g/m2), which resulted in production of higher grain yield as well as net monetary returns over isoproturon, clodinafop and weedy check. Maximum benefit: cost ratio was obtained with 100% available soil moisture along with application of isoproturon.