Study On The High-yield Planting Model Of Double Cropping Forage Grass In The Agricultural Area Of Lhasa River Valley

In Tibet is one of the five major pastoral areas in China,and with the development of animal husbandry in the agricultural area of Tibet,the problems such as the small proportion of artificial grass and shortage of high-quality forage production are becoming increasingly serious.The backward forage cultivation mode leads to insufficient use of light and heat resources;the traditional fertilization mode leads to the destruction of soil ecology and other factors greatly limit the development of the livestock industry in the Lhasa River Valley farming area.To solve the above problems in this area,this study established cultivated artificial grass in Linzhou County,Lhasa,and set up the experiment of introducing three varieties of autumn-sown rye(Lvmai etc.)and six varieties of small rye(Zhongsi1048 etc.)in the autumn of the first year,and set 6 the experiments of different varieties(75 kg/hm~2,150 kg/hm~2,225 kg/hm~2,300 kg/hm~2,450 kg/hm~2,525 kg/hm~2)respectively.In the second summer,after harvesting the autumn sown forage in the same area,the experiment was conducted on nine varieties of oats(Taiyangshen etc.).The summer sowing pattern with the highest yield of oats was explored by setting up the introduction test of nine varieties of oats,and the same six gradient sowing treatments were applied to all varieties as mentioned above;after combining the highest yield patterns of the two seasons,the optimal pattern of double-season forage planting in the region was determined,and the annual forage yield was summarized.And four gradients of T1(40%replacement),T2(60%replacement),T3(80%replacement),T4(100%of)treatments using organic fertilizer instead of traditional nitrogen fertilizer(urea)and two control groups of CK1(full urea application)and CK2(no nitrogen application)were set up in summer to treat two varieties of oats(Qinghai 444 and Qinghaitianyanmai)were fertilized to investigate the highest yielding forage cultivation pattern under the organic fertilizer instead of nitrogen fertilization pattern.The main findings of this study are as follows:(1)In the experiment of autumn-sown rye and small rye,the average fresh and hay yields of Lvmai were the highest,significantly greater than the fresh and hay yields of other varieties;and three varieties of small rye,Zhongsi 1048,Zhongsi 1877 and Zhongsi 3241,also performed better,with no significant difference between them.With the increase in sowing rate,most of the varieties showed a trend of increasing and then decreasing,and the maximum yield was achieved at 300 kg/hm~2to 450 kg/hm2 sowing rate,but some varieties could achieve the maximum yield at other sowing rates due to the interaction of both varieties and sowing rates.Finally,the maximum fresh and hay yields of 25.72 t/hm~2and20.00 t/hm~2were achieved for all fall sowing treatments at 300 kg/hm~2sowing rate,respectively.(2)The average fresh grass yield of three varieties of oats in the oat summer sowing trial,Taiyangshen,Qingmu 1,and Kona,all performed better without significant differences,with the Sun God variety having the highest average fresh grass yield;Sun God and Green Shepherd 1 performed better in terms of hay yield.The fresh grass and hay yields of oats also showed a trend of increasing and then decreasing with increasing gradient,and most oats could reach the maximum yield of their varieties at 300 kg/hm~2sowing rate.At 300 kg/hm~2sowing rate,both fresh and hay yields were the highest among summer sowing treatments,with 20.00 t/hm~2and 12.72 t/hm~2respectively.(3)Combining the optimal planting pattern of autumn sowing and summer sowing,"300 kg/hm~2sowing of Lvmai in autumn+300 kg/hm~2sowing of oats in summer",the annual fresh grass yield of this pattern could reach 45.72 t/hm~2and annual hay yield could reach 27.69 t/hm~2,which is much larger than the annual sowing of oats in the region.(4)As the gradient of organic fertilizer substitution for N fertilizer increases,the fresh and hay yields of forage will also increase significantly;under treatment T4(100%),the fresh and hay yields of forage can be significantly greater than those of treatment CK1 with full urea application.The fresh and hay yields of treatment CK2(not used N application)were significantly smaller than the other fertilizer treatments.The fresh and hay yields of Qinghai 444 in T4 treatment in Linzhou County could reach 17.64 t/hm~2and 10.47 t/hm~2,respectively,and the fresh and hay yields of Qinghai sweet oats could reach 21.08 t/hm2and 10.99 t/hm~2,respectively,The fresh and hay yields of Qinghai sweet oats could reach32.33 t/hm2 and 13.17 t/hm~2.The most suitable model for increasing the yield of artificial grass in the agricultural area of Lhasa Valley is to sow the rye variety Lvmai under 300 kg/hm~2in autumn and the oat variety Taiyangshen in summer,and to choose organic fertilizer instead of traditional urea.This planting pattern can significantly increase the local forage yield.