Herbicide application impacted soil microbial community composition and biochemical properties in a flooded rice field

Sustainable Weed Management: The Effects of Applying Pre- and Post-Emergence Herbicides to Medicago ruthenica

Medicago ruthenica is a forage legume crop that is widely used as fodder and for ecological restoration in arid and semi-arid areas in Northcentral Asia. During the seedling stage, weeds challenge the growth and development of M. ruthenica, especially in fields sown for seed production. However, strategies to effectively control weeds in crops of M. ruthenica using herbicides have not been investigated. We evaluate the efficacy of different herbicides that control pre- and post-emergence of weeds in M. ruthenica. The results indicated that the most effective pre-emergence herbicides, imazethapyr (1530 mL ha-1) and flumetsulam (120 mL ha-1), resulted in crop safety and soil microbial community equivalent to a weed-free check. The most effective post-emergence herbicides are imazethapyr + haloxyfop-P (1800 + 600 mL ha-1) and 2,4-DB + haloxyfop-P (2250 + 600 mL ha-1). These herbicide treatments demonstrate effective control of most weeds (A. retroflexus, C. album, and grasses) while ensuring crop safety. Application of these herbicides to control weeds in M. ruthenica prior to or after their emergence represents a viable strategy for their control and also improve agricultural viability and crop yield and quality. Our research contributes to sustainable agriculture and ecological restoration in arid regions.

Degradation of pretilachlor and fenclorim and effects of these compounds on bacterial communities under anaerobic condition

Pretilachlor and safener fenclorim are the main components of herbicides widely applied to control weeds. Although some pure cultures of bacteria and fungi which degraded these compounds under aerobic conditions were isolated, no isolated pretilachlor- and fenclorim-degrading bacterial strains under anaerobic condition had been available. In this study, the degradation of these compounds and the effects of them on bacterial community structures were investigated under anaerobic conditions. The dissipation rates of pretilachlor and fenclorim in slurries were in the order: soil from paddy field ≈ sediment from river > sediment from mangrove. Moreover, three pretilachlor-degrading bacterial strains (Pseudomonas sp. Pr1, Proteiniclasticum sp. Pr2 and Paracoccus denitrificans Pr3) and two fenclorim-degrading strains (Dechloromonas sp. Fe1 and Ralstonia pickettii Fe2) isolated from a slurry of paddy soil utilized the substrates as sole carbon and energy sources under anaerobic conditions. The degradation of pure pretilachlor and fenclorim at various concentrations by corresponding mixed pure cultures followed the Michaelis-Menten model, with the maximum degradation was 3.10 ± 0.31 µM/day for pretilachlor, and 2.08 ± 0.18 µM/day for fenclorim. During the degradation, 2-chloro-N-(2,6-diethylphenyl) acetamide and 2,6-dimethylaniline were produced in pretilachlor degradation, and benzene was a product of fenclorim degradation. The synergistic degradation of both substrates by all isolated bacteria reduced the metabolites concentrations accumulated in media. This study provides valuable information on effects of pretilachlor and fenclorim on bacterial communities in soil and sediments, and degradation of these substrates by isolated bacteria under anaerobic condition.