Screening and safety evaluation of herbicides in the alfalfa seedling stage in the Hexi area

Alfalfa (Medicago sativa) is widely planted in the Hexi area. However, weeds are one of the main factors affecting yield and quality. It is important to produce high-yield and high-quality alfalfa to carry out research on the screening and safety evaluation of herbicides at the seedling stage. In this study, we explored the effect of different doses of 2, 4-drops of sodium butyrate, imazethapyr and imazethapyr + haloxyfop-P-mehy herbicide on weeds in seedling alfalfa fields, safety, and alfalfa yield. The results show that application during the second-leaf stage was safer than the five-leaf stage, and the alfalfa returned to normal growth rates 24 days after the application. Applying 3 000 mL·ha⁻¹ 2, 4-drops of sodium butyrate and 2 250 mL·ha⁻¹ imazethapyr had a fresh weight control effect of more than 91.02% on redrootpigweed (Amaranthus retroflexus), and 80.90% on quinoa (Chenopodium glaucum). The control effects of spraying imazethapyr or a combination of imazethapyr and haloxyfop-P-mehy on the fresh weight and coverage inhibition rate of Cuscuta (Cuscuta chinensis) were over 92.65% and 93.93%, respectively. We conclude that when Cuscuta is present in alfalfa fields, imazethapyr or imazethapyr + haloxyfop-P-mehy can be used for weed control at the seedling stage. When quinoa and redrootpigweed are present, in order to prevent the emergence of weed resistance, imazethapyr or 2, 4-drops of sodium butyrate may be used, with alternate application.