Abstract
Rice cultivation always remains significant for food and livelihood security. The predictions of increasing water deficiency under a changing climate and escalating labor shortages in agriculture have brought a paradigm swing in rice cultivation from conventionally flooded transplanting to direct-seeded rice (DSR). DSR cultivation can potentially address the concerns of diminishing natural resources and mounting production costs in the establishment of transplanted rice. The transition towards DSR saves water, reduces duration to maturity as well as labor required, and reduces negative environmental footprints. Despite all these recompenses, the potential yield losses through enormous weed menaces under DSR remains a challenge and may reduce yield by up to 50%. In this review, we examine the extent of weed infestation, weed shift and the losses in dry DSR (DDSR). Various regional and global scientific efforts made under DDSR have been assessed in the present and the smart weed-management strategies suggested can be adopted after scrutiny. Integration of different weed management approaches, namely prevention, cultural, mechanical, and chemical, have been discussed, which can pave the way for worldwide adoption of DDSR, especially in South Asia. In Asia, 22% of the acreage of total rice cultivation is under DSR and the region-specific integration of these weed-management approaches might reduce herbicide use in these areas by up to 50%.
Highlights
Rice (Oryza sativa L.) is a primary food crop grown widely over 161 million hectares in more than 100 countries of the world [1]
Several constraints involved with transplanted puddled rice (TPR), namely a huge water demand (1000–2000 mm) for puddling and maintaining continuous flooding [4]; a huge energy requirement ranging between 5630–8448 MJ ha−1 [5] and almost 15–20% higher labor inputs [6] over direct-seeded rice (DSR), have made it unaffordable for many farmers, especially for small and marginal farmers in Southeast Asia [7]
Stale seedbed (SSB) is a cultural method of weed management commonly practiced with tillage, but under zero tillage (ZT)-dry DSR (DDSR) the emerged weed seedlings are destroyed with an application of a nonselective post-emergence herbicide, either paraquat [59] or glyphosate [60]
Summary
Rice (Oryza sativa L.) is a primary food crop grown widely over 161 million hectares in more than 100 countries of the world [1]. The advantages offered by DDSR, namely rapid planting, easy mechanization, less labor and water requirement, and early maturity with fewer environmental footprints have brought almost 22% of the total rice area in Asia under DSR [11,12]. The concurrent crop and weed growth and the absence of standing water in the initial crop establishment phase aggravate weed insurgence in DDSR [21] Under these systems, weeds could be managed by hand weeding (manual means), through herbicides or by a combination of both. There has been grave apprehension about the solitary use of herbicides in the recent past due to the development of resistance in weeds, changes in the weed density and composition, and the emerging negative environmental footprints Amidst these concerns, adoption of any single approach remains both insufficient and ineffective for sustainable weed management in DDSR and the present review emphasizes integrated weed management practices for DDSR. Under double DSR, cycling dry and wet tillage is practiced in Asia [26]; exclusive DDSR is practiced in the United States, Latin America, Australia, West Africa and Europe [27]
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