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Conservation agriculture (CA) technologies involve minimum soil disturbance, soil cover through crop residues or other cover crops, and crop rotations. Weeds are a major constraint in adoption of CA-based technologies. Conservation tillage influences weed infestation, and thus interactions between tillage and weed control practices are commonly observed in crop production. There are reports available that zero tillage increases as well as reduces infestation of certain weed species in different crops. In rainy season when the weed problem is generally more, growing crops with zero tillage requires additional measures for effective weed control, including use of non-selective herbicides like paraquat and glyphosate. Zero-till sowing in standing crop residues along with application of herbicides in proper combination, sequence or in rotation leads to lower weed population and higher yield than conventional planting. However, changing from tillage-based farming to no-till farming is not easy. No-till incurs a greater risk of crop failure or lower net returns than conventional agriculture, and this perception has seriously hindered its adoption in countries outside north and south America. Yields of no-till crops may be lower by 5-10% in the initial years, especially on fine-textured and poorly-drained soils. No-till farming demands use of extra N fertilizer and heavy reliance on herbicides. The continued practice of no-till is, therefore, highly dependent on development of new herbicide formulations and integrated weed management options.

Key words: Conservation agriculture, Crop residues, No-till farming, Non-selective herbicides, Rice-wheat system, Weed management.