刈割高度与施氮量对饲料桑全株产量及营养品质的影响

本研究以饲料桑新品种‘川饲桑1号’（Morus alba cv. Chuansisang-1）为试验材料，采用二因素随机区组设计连续3年（2016-2018）对不同刈割高度（H₁：70 cm，H₂：90 cm，H₃：110 cm）和施氮量（N₁：138 kg N·hm^-2，N₂：207 kg N·hm^-2，N₃：276 kg N·hm^-2）下的饲草产量、植物学特性及营养品质进行测定，并对其饲用价值进行综合评价，以期为饲料桑的推广利用提供数据支撑。结果表明，随着年限的增加各处理下饲草产量逐年递增，且均以H₂N₃处理最高。刈割高度与施氮量对饲料桑产量、植物学特性和营养品质均有影响。其中，刈割高度是影响饲料桑植物学特性的主要因素，两者交互作用对饲草产量、单枝重及各营养指标影响显著（P<0.05）。在相同刈割高度下，鲜、干草产量和中性洗涤纤维均以N₃处理最高，粗蛋白含量随施氮量的增加先增加后减小。在相同氮肥用量下，H₂处理下的大部分饲草产量、主枝叶片数、单株重最大，中性洗涤纤维和酸性洗涤纤维含量整体随刈割高度的增加而增大。粗蛋白和粗灰分含量整体在H₂高度下最高，粗脂肪含量随刈割高度增加呈先升高后降低的趋势。以隶属函数法对‘川饲桑1号’的饲用价值进行综合评价可知，在刈割高度为90 cm、施氮量为276 kg N·hm^-2时其饲用价值最高。

Effect of cutting height and nitrogen fertilizer rate on yield and nutritive value of whole-plant mulberry(Morus alba)

In this study， a two-factor randomized block experiment was conducted to determine the yield， botanical characteristics， and nutritive value of a forage mulberry cultivar （Morus alba cv. Chuansisang-1）. Treatments comprised different cutting heights （H₁： 70 cm， H₂： 90 cm， and H₃： 110 cm） and nitrogen fertilization rates （N₁： 138 kg N·ha^-1， N₂： 207 kg N·ha^-1， and N₃： 276 kg N·ha^-1） in Northeast Sichuan， South China. Feeding value of the forage mulberry under the different treatments was evaluated in order to provide data support promotion and utilization of forage mulberry as an animal feed. It was found that herbage yields increased with age under each treatment， and the treatment combination H₂N₃ had the highest herbage yield. Cutting height and nitrogen application rate both had significant effects on the yield， botanical characteristics， and nutritive value of forage mulberry. Cutting height was the main factor affecting the botanical characteristics of forage mulberry， and there were also significant （P<0.05） cutting height×nitrogen fertilization rate interaction effects on herbage yield， single-branch weight， and nutritive value. At the same cutting height， the herbage yield， and neutral detergent fiber of N₃ treatment were the highest， and the crude protein content was higher in N₂ than in N₁ or N₃， and the herbage yield， the number of leaves on main branches and single plant weight were largest under the H₂ treatment. The contents of neutral detergent fiber and acid detergent fiber increased with increase in cutting height. Crude protein and ash contents were highest at H₂， and crude fat content initially increased and then decreased across the three cutting heights. The feeding value of ‘Chuansisang-1’was evaluated using a multivariate subordinate function analysis and the optimal treatment combination was found to be H₂N₃ （i.e. a cutting height of 90 cm and nitrogen application rate of 276 kg N·ha^-1）.