Abstract: To study the effects of alfalfa (recorded as A in this experiment) and Kentucky bluegrass (recorded as B in this experiment) rotations on their agronomic characteristics and nutritional quality,field that alfalfa (A) and Kentucky bluegrass (K) were planted on for 5 years was selected as the stubble field. Alfalfa (A) and Kentucky bluegrass (K) were planted on the field and 4 rotation modes,AK,KK,AA,and KA,were settled. AK and KA were regarded as rotation cropping,AA and KK models were regarded as continuous cropping. The plant height,dry yield,dry-to-fresh ratio,stem-to-leaf ratio,crude protein (CP),and acid detergent fiber (ADF),neutral detergent fiber (NDF) of alfalfa and Kentucky bluegrass were studied at each cutting to analyze the effects of rotation on the variation of their agronomic characteristics and nutritional quality. The results showed that,from 1~3 cutting,the plant height of Kentucky bluegrass in AK rotation increased by 6.31%~9.47% compared with KK continuous cropping,and the difference was significant in the second cutting (P<0.05). Compared with AA,the plant height of KA alfalfa increased by 6.72%~9.02%,and significant differences were found in the second cutting (P<0.05). The annual dry yield of Kentucky bluegrass in AK rotation was 8.54% higher than that of KK continuous cropping,and the annual hay yield of alfalfa in KA rotation was 11.57% higher than that of AA continuous cropping. Compared with KK continuous cropping,the dry-fresh ratio of Kentucky bluegrass in AK rotation grassland were significantly higher in all the three cuttings (P<0.05),and the increasing range was greater than that of KA rotation relative to AA continuing. The improvement of rotation on stem-to-leaf ratio in different rotation patterns was significantly different in the last two cuttings. The crude protein content of Kentucky bluegrass in AK rotation grassland increased by 14.16%~15.95% compared with KK,and the growth rate was better than that in KA rotation relative to AA continuing model. The contents of neutral detergent fiber and acid detergent fiber under AK rotation and KA rotation were significantly different from KK continuous cropping and AA continuous cropping,respectively (P<0.05). Rotation of alfalfa and Kentucky bluegrass can increase the plant height,hay yield,stem-leaf ratio,and dry-fresh ratio,as well as the crude protein content of the after-stubble pastures;and reduce acid and neutral washing fibers in the subsequent crops. The purpose of this experiment is to explore the changes of agronomic characteristics and nutritional content of pastures under alfalfa and Kentucky bluegrass rotation,and to provide a basis for future legume-grasses rotation,grass seed mix and pattern arrangement.

Key words: Rotation, Alfalfa, Kentucky bluegrass, Agronomic characters, Nutritional quality

摘要： 为研究紫花苜蓿（Medicago sativa，本试验中记为A）与草地早熟禾（Poa pratensis，本试验中记为K）轮作对其农艺性状和营养品质的影响，本试验以种植5年的紫花苜蓿（A）和草地早熟禾（K）为前茬，在2块草地上分别种植紫花苜蓿（A）和草地早熟禾（K），即形成AA，AK，KA，KK 4种种植模式，以AK和KA为轮作处理，AA和KK为连作对照。研究了轮作对紫花苜蓿和草地早熟禾各刈割茬次的株高、干草产量、干鲜比、茎叶比、粗蛋白（Crude protein，CP）、中性洗涤纤维（Neutral detergent fiber，NDF）和酸性洗涤纤维（Acid detergent fiber，ADF）等指标变化的影响。结果表明：第1~3茬，AK轮作草地早熟禾的株高较KK连作提高6.31%~9.47%，且在第2茬差异显著（P<0.05）。KA轮作紫花苜蓿的株高较AA连作提高6.72%~9.02%，且在第2茬差异显著（P<0.05）。AK轮作的草地早熟禾年干草产量较KK连作提高8.54%，KA轮作的紫花苜蓿年干草产量较AA连作提高11.57%。AK轮作草地早熟禾的干鲜比较KK连作在3茬间差异显著（P<0.05），且增加幅度大于KA比AA的增加幅度。不同轮作模式对茎叶比的提高在后2茬差异明显。AK轮作下，草地早熟禾的粗蛋白含量比KK提高14.16%~15.95%，增长幅度优于KA比AA的增加幅度。AK轮作和KA轮作的中性洗涤纤维含量和酸性洗涤纤维在不同茬次较KK连作和AA连作模式差异显著（P<0.05）。紫花苜蓿与草地早熟禾轮作可以提高后茬牧草的株高、干草产量、茎叶比和干鲜比以及粗蛋白含量；并且降低后茬的酸性洗涤纤维和中性洗涤纤维。本试验旨在通过探究紫花苜蓿与草地早熟禾轮作下牧草农艺性状和营养成分的变化情况，为今后豆-禾牧草轮作、草种搭配以及模式排布提供借鉴依据。

关键词: 轮作, 紫花苜蓿, 草地早熟禾, 农艺性状, 营养品质