[Objective] In this study, the control effects of mixed planting of spring wheat and alfalfa on the occurrence rate of weeds in fields were investigated and made clear, and also the effects of conservation tillage on the yield and nutrient quality of alfalfa of the first cut were discussed.[Method]Spring wheat seeding rate gradients included 120 kg/hm2 (S1), 80 kg/hm2 (S2), 240 kg/hm2 (S3), respectively, and alfalfa without sowing was taken as the control (S0).The growth characters of the first cut alfalfa were determined and analyzed.[Result]With the increase of sowing amount, the dry matter yield of spring wheat increased gradually, and the proportion of weeds decreased from 35.3% to 18.4%.The height, stem diameter, stem leaf ratio, hay yield of first cut alfalfa was S1>S0>S2>S3, and the S1 treatment yield was significantly higher than those of S3 and S0 (P0.05) in the year of sowing.The crude protein, neutral detergent fiber, acid detergent fiber, ether extract, calcium and phosphorus content in the first cut alfalfa gradually decreased, and the S1 treatment was significantly higher than the S0 and S3 treatment (PS0>S2>S3处理,且干草产量均为S1处理显著大于S3、S0处理(P0.05);紫花苜蓿播种当年第一茬的粗蛋白质、中性洗涤纤维、酸性洗涤纤维、粗脂肪、钙、磷含量均逐渐减小,S1处理显著大于S0、S3处理(P<0.05),两个苜蓿品种表现出相同的变化规律.[结论]保护播种能够有效降低紫花苜蓿田间杂草比例,综合考虑苜蓿产量及营养品质,当春小麦播种量为120~180 kg/hm2时,紫花苜蓿第一茬草的生产性能最优.
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