Response To Water-saving Irrigation Period In Different Forage Mixing Modes In Alpine Arid Area

Aiming at the problems of insufficient rainfall and low water use efficiency of Artificial Forage in Alpine desert area,the field experiments were carried out in Jintai pasture of Wulan County,Qinghai Province in 2018 and 2019 with oats,arrow peas,quinoa and vetch as the research objects.In 2018,three water treatments were set up: no irrigation in the whole growth period,water saving by irrigation and pulling(25 mm),irrigation and pulling and two water for flowering(25 mm + 25 mm),two mixed planting modes: oats and arrow peas,quinoa and hairy vetch.Based on the mixed sowing of quinoa and vetch in 2018,two growth stages of branching stage and flowering stage are selected in 2019,and three water control gradients are set: medium deficit: soil moisture content of 45%-55% FC,slight deficit: soil moisture content of 55%-65% FC,full irrigation: soil moisture content of 65%-75% FC,with no irrigation in the whole growth period as the control.The effects of irrigation on the yield,water use efficiency,feeding value and soil environment of forage grass mixture were studied.The comprehensive analysis method was used to analyze the effect of irrigation on forage grass mixture,and the optimal irrigation treatment was obtained.The main conclusions are as follows:1.The yield of the mixture of oats,arrow peas,quinoa and hairy vetch increased with the increase of irrigation,and reached the maximum of 21909.38 kg/hm2 and 14432.50 kg/hm2 under the treatment of irrigation,drawing and flowering water,respectively.Compared with CK,the increase of water use efficiency was 58.97% and 26.34%,and the highest water use efficiency was 3.47 kg/m3 and 2.42 kg/m3 without irrigation.Under the condition of regulated deficit irrigation,the yield of the mixture of quinoa and hairy vetch increased in different degrees.The highest yield was 11030.48kg/hm2,the highest yield was 56.13%,and the highest water use efficiency was 2.51kg/m3 at branching stage and flowering stage.2.The content of acid washing fiber(ADF)and neutral washing fiber(NDF)decreased with the decrease of irrigation,the lowest was 23.13% and 48.57% in CK without irrigation,the content of crude protein and relative feeding value(RFV)increased with the decrease of irrigation,the highest was 10.59% and 9.63% in CK without irrigation,and RFV was 136 67%? The content of ADF and NDF decreased with the decrease of irrigation,the lowest was 24.36% and 36.20% in L1,the highest was 10.95% and 18.48% in L1,and the highest was 180.33% in L1.Under the condition of regulated deficit irrigation,the content of crude protein in quinoa and sweet potato was 19.10% at the highest level without irrigation.ADF and NDF decreased with the decrease of water deficit,the lowest value was 23.06% and 33.10% in CK and the highest value was 199.60% in RFV.3.In the whole growth period,the soil volume moisture content of 0-60 cm in the mixed grassland of oats,arrow peas,quinoa and hairy vetch increased with the increase of irrigation,which could keep the normal growth of forage grass in the later period.The change range of soil temperature decreased with the increase of irrigation,which was beneficial to the stable ground temperature.Under the treatment of water deficit regulation,the soil moisture content in different growth periods decreased with the increase of water deficit regulation.In the 0-40 cm soil layer,with the decrease of water deficit,the content of soil alkali hydrolyzed nitrogen decreased;the content of soil available phosphorus decreased first and then increased;the content of soil available potassium and soil organic matter increased first and then decreased.4.According to the analysis,in 2018,under the mixture of oat and arrow pea,under the treatment of irrigation and pull water saving and flowering water Y2,the comprehensive performance was the best,which was 86.10% water saving compared with the general flood irrigation,which was the optimal irrigation treatment;under the mixture of quinoa and vetch,under the treatment of irrigation and pull water saving L1,the comprehensive performance was the best,which was 93.05% water saving compared with the general flood irrigation,which was the optimal irrigation treatment.Therefore,these two irrigation modes are the optimal irrigation modes for the local production of two forage grass mixture.In 2019,under the condition of regulated deficit irrigation,the comprehensive characters of quinoa and hairy vetch mixed sowing were the best in the light deficit irrigation(55%-65%)at branching stage and flowering stage.Compared with the general flood irrigation,the comprehensive characters of T5 treatment were 71.15%,which was the best irrigation treatment.It is the best mode of regulating water deficit for the local production of quinoa and hairy vetch mixed.