Published in: Indian Journal of Weed Science, 46(1): 31–35, 2014.
It was 20 years ago which marked the beginning of conservation agriculture (CA) with introduction of zerotillage (ZT) in wheat to (1) reduce cultivation cost so that farmers can afford to purchase new but expensive alternate herbicides for the control of herbicide-resistant population of Phalaris minor Retz., the most troublesome weed of wheat, and (2) reduce land preparation period for timely wheat planting. Worldwide, CA has spread mostly in the rain-fed agriculture but India witnessed its success more in irrigated rice-wheat cropping systems (RWCS) of the Indo-Gangetic Plains (IGP). High input based crop culture in the North West IGP has enabled weeds such as P. minor in wheat and Echinochloa crusgalli (L.) Beauv. in rice to dominate the weed flora. In wheat, zero tillage (ZT) is widely adopted by farmers in North West India and recently it is widely accepted by farmers in the eastern IGP also. In North West India, under ZT wheat, emergence and biomass of P. minor was reduced, but weed flora shifted toward more broad-leaf weeds such as Rumex dentatus (L.). In the Eastern IGP, perennial weeds such as Cynodon dactylon L. Pers. and Cyperus rotundus L. are also problematic weeds in some cases under ZT. In rice, the focus now is on dry direct-seeded rice (DSR) and machine transplanting of non-puddled rice (MTNPR) as an alternate option to puddled transplanted rice (PTR). Shifting from PTR to DSR results in changes in tillage, crop establishment method, water and weed management which often results in changes in weed composition and diversity. Weedy rice has emerged as a major threat for DSR in countries where DSR is widely adopted. In the eastern IGP, Physallis minima and Cyperus rotundus are also becoming major problematic weeds in DSR. Increased net profit for farmers by using this new technology was the main reason for rapid adoption of ZT. Since 2009, the Cereal Systems Initiatives for South Asia (CSISA), project funded by Gates Foundation and USAID and implemented by four consultative group on International Agricultural Research (CGIAR) (CG) Centers (CIMMYT, IRRI, IFPRI and ILRI) in collaboration with national partners, has explored options for sustainable intensification across the IGP, including CA-based crop management. This paper highlights the weed management scenario in conservation agriculture in India.
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