Carry-over effect of metribuzin applied to soybean (Glycine max) on weeds and wheat (Triticum aestivum) under zero and conventional tillage

摘要

Effective weed control in no-till systems is mainly dependent on herbicides. Appropriate weed management strategies, however, can reduce the amount of herbicides. In this study possible weed management was attempted in wheat (Triticum aestivum L. emend. Fiori & Paol.) under zero-tillage (without residue) and conventional tillage between 2006-07 and 2007-08 following residual effects of 13 weed control treatments, with metribuzin applied during previous rainy (kharif) seasons, 2006 and 2007 in soybean [Glycine max (L.) Mirrill]. The experiment was laid out in a split plot design with three replications. Total density of weeds did not differ significantly between weed control measures adopted during previous rainy season. But, conventional tillage (CT) caused a significant reduction in the populations of grass, broad-leaved (e.g., Chenopodium album L. and Melilotus indica L.) and total weeds when compared with zero-tillage (ZT) without crop residues. Similarly, higher nutrient removal by weeds was under zero-tillage than under conventional tillage. In general, residual effect of all the previous season metribuzin treatments was more pronounced on the grasses (Phalaris minor Retz. and Avena sterilis ssp ludoviciana Dur.) when compared with Chenopodium album and Melilotus indica. Wheat yield was similar in all previous season metribuzin treatments except in weed-free check in both years. However, metribuzin at 0.5 kg/ha pre-emergence, on yield, was more effective, indicating its considerable residual effect on weeds in wheat. This treatment also gave the highest net benefit:cost ratio.