Purpose This study aimed to clarify the weed community structure characteristics in aerobic paddy fields, and to evaluate the efficacy and crop safety of six commonly used chloroacetamide herbicides so as to provide a scientific basis for precise weed management in next generation dryland rice (NGDR) field.
Methods Field investigations and comparative trials were conducted in Zhutang Township, Lancang Lahu Autonomous County, Puer City, Yunnan Province. An inverted “W”-shaped nine-point sampling method was used for weed community investigation, and the dominance levels of weed species were evaluated by calculating community ecological indices. A completely randomized block design was used for herbicide efficacy trials, with efficacy surveys at 14, 28, and 42 days after application, assessing the impacts of herbicides on rice growth and yield.
Results A total of 14 weed species belonging to seven families were identified, all of which were xerophytic types. The dominant species were Digitaria sanguinalis, Ageratum conyzoides, Bidens pilosa, Eleusine indica, Galinsoga parviflora, and Commelina benghalensis. The efficacy trial results showed that 900 g/L acetochlor and 960 g/L S-metolachlor showed the best control efficacy against Poaceae weeds and broadleaf weeds, but significantly inhibited rice growth (plant height inhibition rate>25%). 300 g/L pretilachlor and 60% butachlor demonstrated the best crop safety (plant height inhibition rate<3%) and compensatory growth promotion effects. The highest rice yield was obtained with 300 g/L pretilachlor treatment (6.71 t/hm2, with a yield increase rate of 30.80%), followed by 60% butachlor (6.49 t/hm2, with a yield increase rate of 28.49%).
Conclusion In weed management of NGDR fields, herbicide crop safety and efficacy are equally important. It is recommended to prioritize using 300 g/L pretilachlor (emulsifiable concentrate, EC) or 60% butachlor (EC) as the main herbicides for pre-emergence control of Poaceae weeds in NGDR fields in southwestern China.
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