Journal of Research in Weed Science
Volume:5 Issue: 2, Jun 2022

This field experiment was carried out at Agricultural Research Farm of Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, during the Kharif season of 2016 and 2017. The experiment was established in a split-plot design with three replicates and comprised of total 15 treatment combinations involving three crop establishment methods as: (i) conventional till-direct seeded rice, (ii) the conventional till-wet direct-seeded rice, and (iii) and zero till-direct seeded rice in the main plot and five Zn application treatments (i) control (No Zn application), (ii) 3 kg Zn ha-1 (basal application), (iii) 3 kg Zn ha-1 (foliar application), (iv) 6 kg Zn ha-1 (basal application), and (v) 6 kg Zn ha-1 (foliar application) in the subplot. The crop establishment methods significantly (p=0.05) influenced weeds density and dry weight at 20, 40, 60, and 80 days after sowing. Among crop establishment methods, the conventional till-wet direct-seeded observed the lowest density and dry weight of grassy, sedge, and broad-leaf weeds across all the crop growth stages. Concerning crop yield, the conventional till-wet direct-seeded rice and 6 kg Zn ha-1 (basal application) recorded higher grain, straw, biological yield, and harvest index. Thus, it is suggested that conventional till-wet direct-seeded rice and 6 kg Zn ha-1 (basal application) can be practiced for recording the higher yields and the effective management of weeds in DSR.

Halfa or cogongrass (Imperata cylindrica L.) is one of the noxious/problematic species which not only threatens agriculture productivity, but also causes environmental damage to the ecosystem, whereas the invasive alien weeds are affected greatly by seed germination that depends on the temperature and light as well as other environmental factors. Therefore, the germination behavior of I. cylindrica at the optimum temperature regimes (25/35 °C) was chosen to test the effect of different light regimes, some growth regulators i.e. indole butyric acid (IBA), gibberellic acid (GA3), and naphthalene acetic acid + naphthalene acetamide (NAA + NAD), and chemical substances i.e. Potassium nitrate (KNO3) and Si-Si-6, acetic acid on seed germination of cogon grass (I. cylindrica). The higher germination percent of I. cylindrica seeds was observed after soaking for 12 hours in the growth regulators at 200, 800, 400, and 1000 ppm which exhibited germination of 56.67, 71.11, 73.33, and 56. 67% after soaking in gibberellic acid and 65.56, 71.11, 73.33, and 56.67% after soaking in indole butyric acid, respectively under 16/8 hours of light/darkness. The maximum germination of I. cylindrica seeds (22.44%) was also achieved after exposure to 1% acetic acid for 1min. under 16/8 h light/ dark and the same temperature, while the greater level of germination (55.56% and 35.56%) was attained after 12 h. soaking in 10% from Si-Si-6 (Potassium sulphonate 10% SL) and KNO3, respectively. It can be concluded that I. cylindrica germination rate depends on the environmental factors and its time of exposure which are the driving force for changes in I. cylindrica seed dormancy. This information could help in preventing and predicting their invasion as well as may lead to improving its management strategies.

Rumex dentatus L. (toothed dock), a major broadleaf weed, is a severe problem of irrigated wheat in particularly no-till conditions of the rice-wheat system in India. Metsulfuron is being used for its control. However, the sole reliance on metsulfuron has led to its resistance evolution in R. dentatus. Pot bioassay studies confirmed high level of metsulfuron resistance with GR50 values ranging 74 to 98 times to that of the most susceptible population. Metsulfuron resistant (MR) populations had indicated cross-resistance to other ALS inhibitor herbicides, triasulfuron, pyroxsulam, and florasulam. The ready-mix combination of halauxifen methyl + florasulam was also poor against MR populations. The most sensitive and resistant populations had GR50 values of 0.11 and 10.31, 1.0 and 269.5, <0.94 and >30, <1.13 and 3622.5, 0.16 and 10.14 g/ha for metsulfuron, triasulfuron, florasulam, pyroxsulam, and pre-mix of halauxifen + florasulam, respectively. Results showed a high resistance level in R. dentatus against ALS inhibitor herbicides. In addition, a large number of populations (119) were also screened across broad herbicide groups used in wheat and 68.9 % populations exhibited ≤ 50 % control with a recommended field rate of metsulfuron 4 g/ha, indicating the widespread resistance. However, MR- populations were sensitive to pendimethalin, isoproturon, 2,4-D, fluroxypyr, metribuzin, carfentrazone and flumioxazin. So, these herbicides in rotation and as mixture can be used to manage ALS inhibitor herbicide resistance. However, for long-term sustainable management of herbicide-resistant R. dentatus, alternative herbicides should be integrated with best agronomic practices to restrict its infestation in wheat.

Over the past decades, human and natural changes had led to an increase in the diversity and abundance of weeds in cultivated lands of not only Senegal, but also across the world. However, weed structure and dynamics were not well-known by local populations. This research intended to study some cultural practices and some factors that can influence the weeds presence in rice crops. Therefore, a survey and inventory were carried out at Badiatte and Essyl. Interviews by using a questionnaire were done on cultural practices and perceptions of local populations. To study the dynamics and structure of weeds, the quadrant point method was used. Abiotic factors that can influence the weeds presence, such as soil texture and pH were determined. In total, 31 species belonging to 25 genera and 11 families were inventoried in the two villages. The Cyperaceae (Cyperus rotundus L., Cyperus esculentus L., Killinga pumila Michx., Cyperus amabilis Vahl, Fimbristylis littoralis Gaudich, Pycreus macrostachyos Lam., Schoenoplectus senegalensis Steud., Fimbristylis hispidula (Vahl) Kunth followed by Fabaceae (Desmodium triflorum L.), and Amaranthaceae (Amaranthus viridis L.) were most abundant in terms of individuals. The specific diversity was higher in Badiatte. The structure and dynamics of weeds changed over time due to the agricultural practices and management. They differed from one site to another depending on maintenance practices, soil preparation, and environmental conditions. The weeds evolution was influenced by soil proprieties and cultural practices (ploughing, varieties cultivated, weeding, and fertilization).