Application of glyphosate [N‐(phosphonomethyl) glycine]‐containing herbicides and tillage, alone or in combination, has been the standard for removing declining alfalfa (Medicago sativa L.) stands. With glyphosate no longer an option to control glyphosate‐resistant alfalfa, different termination strategies are needed. Field studies across four site‐years in Utah evaluated the effect of tillage type and timing (fall conventional till, spring conventional till, fall strip‐till, spring strip‐till, and no‐till) and herbicide timing (fall, spring, in‐crop, and no herbicide) of 2,4‐D (2,4‐dichlorophenoxyacetic acid) and dicamba (3,6‐dichloro‐2‐methoxybenzoic acid) on penetration resistance, alfalfa regrowth, corn (Zea mays L.) emergence rate, and silage corn yield. Across tillage treatments, fall, spring, and in‐crop herbicide timings compared with no herbicide reduced alfalfa stem count and biomass by at least 74 and 92%, respectively. Emergence rate was greatest under fall and spring conventional till or spring strip‐till compared with fall strip‐till or no‐till. Silage corn yield was greatest and similar with fall or spring herbicide applications for all tillage systems and conventional tillage with an in‐crop herbicide application (19–27 Mg ha⁻¹), followed by in‐crop herbicide application for conservation tillage systems and fall and spring conventional till without herbicide application (14–20 Mg ha⁻¹), and lastly when only conservation tillage was used to terminate alfalfa (5–15 Mg ha⁻¹). Silage corn yield can be optimized when glyphosate‐resistant alfalfa is terminated with herbicides prior to planting, regardless of tillage type or timing. Termination of glyphosate‐resistant alfalfa by herbicides after corn emergence, depending on tillage, reduces silage corn yield 9–19%.

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耕作方法和抗草甘膦的苜蓿终止时间会影响土壤性质和随后的玉米产量

单独或组合使用含草甘膦[N-（膦酰基甲基）甘氨酸]的除草剂和耕作是去除下降的紫花苜蓿（紫花苜蓿）林分的标准。由于草甘膦不再是控制抗草甘膦苜蓿的选择，因此需要不同的终止策略。在犹他州四个站点年的田间研究评估了耕作类型和时间（秋季常规耕作，春季常规耕作，秋季脱耕，春季脱耕和免耕）和除草剂定时（秋季，春季，春季）的影响。 2,4-D（2,4-二氯苯氧基乙酸）和麦草畏（3,6-二氯-2-甲氧基苯甲酸）的农作物，没有除草剂）的抗渗透性，苜蓿再生长，玉米（玉米）L.）出苗率高，青贮玉米产量高。在整个耕作处理中，与没有除草剂相比，秋季，春季和作物内除草剂的施用时间分别使苜蓿茎数和生物量分别减少了至少74％和92％。与秋季免耕或免耕相比，秋季和春季常规耕作或春季免耕耕作的出苗率最高。在所有耕作系统中，青贮玉米产量最高，与秋季或春季除草剂施用情况相似，常规耕作与农作物除草剂施用（19–27 Mg ha ^-1）相似，其次为保护性耕作系统和秋季施用农作物除草剂春季和春季常规耕作，不使用除草剂（14–20 Mg ha ^-1），最后仅使用保护性耕作终止苜蓿（5–15 Mg ha^-1）。当抗草甘膦苜蓿在播种前用除草剂终止时，无论耕作类型或时机如何，均可优化青贮玉米的单产。玉米出苗后，除草剂可终止抗草甘膦的苜蓿的生长，具体取决于耕作，使青贮玉米的产量降低9-19％。