To commensurate with the Govt. of India’s mission “Bharat ka Amrut Mahotsav” commemorating 75 years of India’s Independence, an International Webinar on “Role of weed biology in improving weed management strategies” was organized on 22-06-2021.The lead speaker Dr. B.S. Chauhan, Professor (Weed Science), the University of Queensland, Australia, very comprehensively delivered the talk covering different aspects of weed biology including weed seed dormancy and germination, phenology, competitive ability, reproductive biology, seed bank dynamics, seed persistence etc., and effect of environmental factors such as light, temperature, climate change effect in respect to elevated carbon dioxide, temperature and water, drought; and management practices like tillage on weed seed germination and reproductive capacity. Weeds are one of the major biotic stresses in agriculture, causing >11 billion US$ economic loss annually to Indian farmers in 10 major crops only. In addition, problem of herbicide resistant in weeds is also increasing, and no new herbicide molecule with different mode of action has been developed since last three decades. Therefore, proper knowledge and understanding of weed biology and ecology is required to develop sustainable weed management practices. It is very much required to understand that how some of the weed biology parameters can be used for developing IWM practices. Dr. Chauhan nicely articulated the need of basic research on weed biology for the future weed management. Dr. Chauhan talked about the effect of light and seed burial depth on germination and emergence of different weed seeds. Some of the weeds like Sonchus spp. and Malva spp. do not require light for germination. Night cultivation could also results in significant reduction in weed density of Chenopodium and Amaranthus. Dr Chauhan also narrated the examples of the farmers in Australia that to prevent the germination of weeds they do cultivation during night. He also cited the examples that how no-tillage (NT) affects weed seed germination. In NT, most of the weed seeds accumulate on surface soil, and one deep tillage after 7-8 years is required to burry these weed seeds deep in the soil. Seeds of Echinochloaspp. can germinate even after the crop canopy closure. Seeds of Leptochloachinensis does not germinate if placed >0.5 cm depths. More than 90% weed seedlings emerge from top 2.0 cm soil.

Temperature also plays an important role in weed seed germination. Some population showed higher germination at lower temperature. Weeds may change seasonality and become major weed in other seasons as well. He quoted the examples of Sonchus, Rye grass and Chenopodiumalbum. To break the physical dormancy due to hard seed coat, scarification is required. Tillage systems affects the seed burial depth and also influences the seed dormancy. The knowledge of weed emergence pattern will help in developing the decision support system (DSS) on weed management, he added. Water stress also influences the plant growth and herbicide efficacy by influencing opening of stomata. Efficacy of glyphosate is reduced at high temperature. Similarly, the efficacy of herbicide is also reduced at elevated CO2 level due to larger plant size. Chairman Dr. Malik while summarizing the whole discussion emphasized that the knowledge of weed biology is required to develop sustainable IWM practice. A network programme on studying weed biology involving AICRP-WM centres is required, he added. More than 300 participant including scientists and students from various ICAR Institutes and Universities attended this webinar through virtual mode besides 103 on Facebook and 7 on UTube. After the deliberation, there was a very fruitful discussion. Many weed scientist shared their views. A lot of questions were posted in chat box by scientist and students. Those questions which were not taken during the discussion due the paucity of time, have been sent to Dr. Chauhan with the request to reply individually. Sushil Kumar, President, ISWS and Convener of the programme, proposed the vote of thanks.

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