划区轮牧对放牧型紫花苜蓿人工草地产量与品质的影响

为探究划区轮牧对放牧型紫花苜蓿（Medicago sativa L.）人工草地产量与品质的影响，本研究开展周期为36 d的6个小区划区轮牧试验，通过对在牧期和牧后再生期紫花苜蓿地上生物量与粗蛋白、粗脂肪、粗灰分、中性洗涤纤维、酸性洗涤纤维指标含量的测定，研究在牧期和牧后再生期紫花苜蓿产量与品质的变化规律，以期为轮牧制度的合理制定提供依据。结果表明：7—8月进行划区轮牧时，在牧期紫花苜蓿的产量和品质均随放牧时间的延长而降低，根据地上生物量和粗蛋白含量的降低量计算出苜蓿草地平均每天为每只羊提供的干物质和粗蛋白量分别为1.65 kg和318 g。牧后再生期紫花苜蓿的产量随时间的延长而升高，品质则随时间的延长先升高后降低，在21 d时品质最好，经过30 d的再生，地上生物量可达3.73 t·hm^-2，粗蛋白产量可达0.8 t·hm^-2。另外，由于绵羊采食的选择性，导致仅剩木质化茎秆的残茬对再生初期苜蓿品质的影响较大，建议牧后对残茬进行刈割以提升再生期草品质。

Yield and Quality Changes of Alfalfa in Response to Rotationally Grazing

An experiment was conducted to study the yield and quality changes of alfalfa in response to rotationally grazing. A 36-day rotation in 6 alfalfa paddocks grazed by lambs was set and a series of indexes during grazing and post-grazing regrowth period were determined respectively, which included the aboveground biomass, the content of crude protein, ether extract, ash, neutral detergent fiber and acid detergent fiber. The results showed that the yield and quality of alfalfa decreased gradually with increasing the duration of grazing in July and August. According to the decrease amount of aboveground biomass and CP content, an average of 1.65 kg dry matter and 318 g CP were provided to each lamb per day by alfalfa pasture. The yield of alfalfa increased with the endurance of alfalfa regrowth, while the quality of alfalfa increased initially and then decreased gradually. The quality reached the peak at 21 d. After a 30-day of regrowth, the aboveground biomass and the yield of crude protein reached 3.73 t·hm^-2 and 0.8 t·hm^-2, respectively. In addition, the stubble with only lignified stems caused by the selective feeding of sheep had significant influence on the quality of alfalfa in the early regrowth stage, so cutting stubble immediately after grazing was recommended in order to improve the quality of alfalfa.