Effects Of Rotation Grazing Of Sheep On The Productivity Of Perennial Sown Grassland In Hexi Oasis

Sown grassland is one of the important symbols of modernization of agriculture.China is among the major countries with the fastest development rate of sown grassland in the world.It is an urgent problem to improve the sown grassland productivity of the sown grassland in order to meet the demand of herbivorous and livestock products for the rapid increase of population and the development of human society for herbivorous animal products.In order to clarify the effect of grazing on the productivity of sown grassland,this paper studied the effects of rotational grazing of sheep on the productivity of three perennial Legume-Gramineae sown grassland including Medicago sativa + Festuca arundinacea（M+F）,Medicago sativa + Bromus inermis（M+B）,Medicago sativa + Festuca arundinacea + Bromus inermis（M+F+B）,and perennial Gramineae sown grassland including Festuca arundinacea + Bromus inermis + Lolium perenne（F+B+L）in Hexi Oasis.The main results are described as follows:（1）Effect of rotational grazing on grass yield and nutrient quality of perennial sown grasslandIn 2020 and 2021,under mowing and rotational grazing,the grass yield of the four perennial sown grassland could be fitted with Logistic growth curve with the increase of growth time,and M+F+B had the highest grass yield.Compared with mowing,rotational grazing increased the grass yield of M+F,M+F +B and F+B+L by 36.46%and 25.36%,29.45% and 11.44%,17.25% and 6.03%,respectively（P < 0.05）and had no significant effect on M+B.The contribution rate of plant height growth rate to hay yield in M+F,M+B and M+F+B was 45.20%,54.40% and 28.60%,respectively,and the contribution rate of tillering density to hay yield in F+B+L was 31.50%.In 2020 and 2021,compared with mowing,the crude protein contents of M+F,M+B,M+F+B and F+B+L were increased by 23.81% and 15.03%,11.70% and 44.92%,14.42% and28.40%,17.31% and 25.08%（P < 0.05）.（2）Effects of rotational grazing on the productivity of livestock in perennial sown grasslandThe average daily body weight gain（ADG）of perennial Legume-Gramineae sown grassland was higher than that of perennial Gramineae sown grassland.For perennial Legume-Gramineae sown grassland and perennial Gramineae sown grassland,the ADG with the dry matter intake（DMI）in a "hump-shaped" curve.In 2020 and 2021,the ADG of perennial Legume-Gramineae sown grassland was higher than perennial Gramineae sown grassland respectively 14.42% and 28.40%（P < 0.05）.The contribution rate of forage crude protein content to DMI in M+F,M+B and M+F+B was 34.40%,37.90%and 22.10%,respectively.And The contribution rate of forage grass yield to DMI in F+B+L was 45.50%.（3）Effects of rotational grazing on soil physical properties in perennial sown grasslandCompared with mowing,rotational grazing effectively increased soil water content,decreased soil p H value and soil salt content in cultivated grassland in 2020 and 2021.In 2020 and 2021,M+F,M+B,M+F+B and F+B+L grassland grazing soil moisture content is higher than the mowing respectively 3.32%-8.97% and 0.09%-24.11%,0.13%-6.43% and 3.60%-9.81%,1.49%-10.64% and 0.01%-26.63%,1.47%-3.44%and 0.69%-3.59%.In 2020 and 2021,M+F,M+B,M+F+B and F+B+L grassland grazing soil p H value is lower than the mowing respectively 0.14%-0.35% and 0.04%-0.86%,0.75%-1.01% and 0.66%-1.16%,0.27%-0.60% and 0.33%-0.62%,0.09%-0.40%and 0.06%-0.25%.In 2020 and 2021,M+F,M+B,M+F+B and F+B+L grassland grazing soil salt content lower than mowing 3.70%-9.80% and 0.13%-17.76%,11.42%-28.07% and 6.85%-31.39%,0.30%-34.17% and 13.08%-36.88% and 2.60%-11.79%and 10.57%-18.19%.