深松浅旋对半干旱区退化紫花苜蓿人工草地改良效果研究

针对半干旱区退化紫花苜蓿人工草地饲草产量低、品质差问题，试验采用单因素随机区组设计，研究了不同深松浅旋程度：深松30 cm+浅旋5 cm（S₁Q₁），深松30 cm+浅旋10 cm（S₁Q₂），深松40 cm+浅旋5 cm（S₂Q₁），深松40 cm+浅旋10 cm（S₂Q₂），深松50 cm+浅旋5 cm（S₃Q₁），深松50 cm+浅旋10 cm（S₃Q₂）以及不做处理（CK）对半干旱区退化紫花苜蓿草地土壤理化性质、生产性能及饲草品质的影响，并利用主成分分析（PCA）方法评价其改良效果。3年试验结果表明，深松浅旋能够不同程度降低紫花苜蓿草地土壤容重，增加土壤孔隙度，显著提高紫花苜蓿株高、分枝数和叶茎比。其中，S₂Q₁处理可降低0~40 cm土层土壤容重，S₂Q₂处理可提高紫花苜蓿分枝数、干草产量和粗蛋白含量，降低中性洗涤纤维、酸性洗涤纤维含量。经PCA综合分析，紫花苜蓿干草产量、叶茎比和粗蛋白贡献率较大，牧草相对饲喂价值和中性洗涤纤维贡献率较小；深松浅旋S₂Q₂处理能够获得较高的紫花苜蓿干草产量（6505.44 kg·hm^-2）和粗蛋白含量（20.74%）；综合性状排名由高到低依次为S₂Q₂，S₁Q₂，S₂Q₁，S₃Q₂，S₁Q₁，S₃Q₁，CK。由此说明，深松40 cm+浅旋10 cm对半干旱区退化紫花苜蓿草地改良效果最优。

Combined ploughing and tilling to improve degraded alfalfa (Medicago sativa) stands in a semi-arid region

Degraded alfalfa （Medicago sativa） stands in semi-arid regions have a low forage yield and poor forage quality， but may be improved by management methods such subsoiling. We conducted a 3-year field experiment with a single factor randomized block design to study the restorative effects on soil physical and chemical properties of subsoiling combined with shallow rotary tilling： plowing to 30 cm+tilling to 5 cm （S₁Q₁）， plowing to 30 cm+tilling to 10 cm （S₁Q₂）， plowing to 40 cm+tilling to 5 cm （S₂Q₁）， plowing to 40 cm+tilling to 10 cm （S₂Q₂）， plowing to 50 cm+tilling to 5 cm （S₃Q₁）， plowing to 50 cm+tilling to 10 cm （S₃Q₂） and control （CK）. Production performance and forage quality of degraded alfalfa grassland were determined， and a principal component analysis （PCA） was used to evaluate the improvement effects of the treatments. It was found that plowing with shallow rotary tilling reduced the soil bulk density， increased soil porosity， and led to significant increases in the plant height， branch number， and leaf∶stem ratio of alfalfa. Among the treatments， S₂Q₁ reduced the soil bulk density in the 0-40 cm soil layer， and S₂Q₂ increased the branch number， hay yield， and crude protein content in alfalfa， and reduced the neutral and acid detergent fiber contents. The results of the PCA indicated that the treatments had larger effects on alfalfa hay yield， leaf∶stem ratio， and crude protein content， and smaller effects on the forage relative feeding value and neutral detergent fiber content. The S₂Q₂ treatment with deep loosening by plowing and shallow tilling led to a high alfalfa hay yield （6505.44 kg·ha^-1） and crude protein content （20.74%）. The treatments were ranked， from largest effects on the multivariate performance score for alfalfa forage to smallest， as follows： S₂Q₂，S₁Q₂，S₂Q₁，S₃Q₂，S₁Q₁，S₃Q₁，CK. Therefore， plowing to 40 cm+tilling to 10 cm was found to be the most effective treatment for improving degraded alfalfa stands in this semi-arid area.