Recent Developments in Rice Weed Management in India

Adusumilli Narayana Rao and Nimal Chandrasena

Keywords:

rice weeds, herbicides, mechanical weed management, robotics, drones, automation, herbicide-tolerant rice

Abstract:

Rice is one of the major staple foods of India. India needs to produce 84 million tons more food grains than it currently produces (315.6 million tons) to meet the demands of 1.65 billion people by 2050. Weeds are among the most severe constraints in resource use efficiency in direct-seeded rice (DSR) than traditionally practiced puddled transplanted rice (TPR). The needed increase in rice production is possible with increased productivity of rice. However, it requires major interventions and system improvements to alleviate the pressure from weeds. In this mini-review, we studied the recent developments in weed management research in rice in India, especially herbicide combinations that might significantly improve the future outlook. Several well-known rice weeds, including Leptochloa chinensis, Ischaemum rugosum, Paspalum distichum, weedy rice and algal blooms, have increased in abundance in rice in some Indian states. A novel method of direct seeding called ‘Tar-wattar DSR’ was introduced and successfully popularised in Punjab. In Jammu also, the Tar-wattar technology resulted in higher returns, but in Haryana, it did not perform well. Two RobiNOweed Basmati rice varieties, Pusa Basmati 1979 and Pusa Basmati 1985, the first non-GM (genetically modified) Basmati rice varieties tolerant to herbicide imazethapyr, have been released recently for commercial cultivation in India. A cautious approach is suggested for their popularisation amongst Indian farmers as non-adoption of stewardship guidelines leads to herbicide-tolerant weedy rice evolution, as has occurred in other countries. Herbicide mixtures and sequential application of herbicides have been found to effectively manage many problematic weeds in rice, established by different methods. Herbicide applications using drones are being tested but are yet to be approved by the Indian government. Efforts are also underway to use machine-vision technology, together with rapid data processing, to enable commercial automated devices and robotic machines to recognise weeds and crop-row patterns and facilitate the treatments against weeds. These methods are yet to be widely tested in rice. More research efforts are needed to have a holistic understanding of climate change effects on weeds in rice, their competition and management, even though such efforts were initiated in India. The research on rice weed management needs to be intensified, focusing on climate-resilient integrated ecological weed management with a major emphasis on cultural and preventative weed management, integrated with the ‘need-based’ use of herbicides and precision weed management.