Study On Water Demand And Consumption Of Spring Highland Barley In Linzhi,tibet

Food security depends on water resources to a great extent.Water resources in Tibet are unevenly distributed in time and space,and agricultural water consumption is large.There are few researches on the basic theory of crop irrigation in the high altitude area of Tibet.It is an urgent problem to further improve the level of agricultural development and crop water use efficiency on the basis of high yield and increase production.According to the main crops in Tibet-spring highland barley,the research on the water consumption law of spring highland barley will play an important role in standardizing the irrigation mode in Tibet,changing the idea of irrigation,enhancing the awareness of water conservation,and improving the rate of agricultural water use.In view of this,in2018-2019,through field experiment and barrel experiment,this paper studied the water consumption law,growth process,yield,water use efficiency and crop coefficient of spring barley,and proposed the water production function of spring barley suitable for Linzhi Region of Tibet.The main conclusions are as follows:(1)0 ～ 30 cm soil layer is sensitive to the change of soil moisture.When the lower limit of controlled soil moisture content in the whole growth period is80-85%,75-80%,65-70%,55-60%,45-50% of the field water capacity,the water consumption of spring barley in the whole growth period is 587.24,569.17,546.22,545.17,524.56,262.5mm respectively,and the water consumption of dry land treatment in the whole growth period is 262.50 mm.During the whole growth period,the water consumption of spring highland barley under different water treatment showed the law of "increase decrease increase".The water consumption of jointing stage and heading stage is the largest,accounting for 26.60% and 22.18% of the total water consumption of the whole growth period,respectively,and the water consumption of seedling stage and milk maturity stage is the smallest,accounting for 10% of the total water consumption of the whole growth period.The water deficit in different growth stages leads to the decrease of water consumption in this growth stage and the whole growth stage of spring barley.The water deficit in seedling stage can increase the water consumption in heading stage and maturity stage of spring barley.The total water consumption gradually decreases with the increase of water deficit from jointing stage to heading stage and from milk maturity stage to maturity stage.Under each water treatment,the water consumption of spring highland barley showed the rule that the larger the irrigation amount was,the larger the water consumption was.(2)Compared with the irrigation treatment in the whole growth period of spring highland barley,the water use efficiency of dry land treatment is the highest,which is 1.52kg/m3,and the yield is the lowest,which is4264.27kg/hm2.Different irrigation treatments in the whole growth period had no significant effect on the plant height,leaf area,dry matter,ear length and grain number of spring barley,and with the aggravation of water deficit,the yield,harvest index and water use efficiency of spring barley increased first and then decreased.Under irrigation treatment,when the soil water content of the whole growth period of spring barley is 65% ～ 70% of the field water capacity,the yield,harvest index and water use efficiency of spring barley are the largest,which are 6117.58 kg / hm2,0.361 and 1.20 kg / m3 respectively.Compared with the full irrigation treatment in the whole growth period,the continuous severe water deficit from jointing stage to heading stage and from milk maturity stage to maturity stage significantly reduced the yield of spring highland barley,with the reduction rates of 33.58% and 26.36% respectively;the water use efficiency gradually increased with the increase of water deficit from jointing stage to heading stage.(3)In the field experiment,the water demand of spring highland barley in the whole growth period showed the law of "increase decrease increase".The total water demand of spring highland barley in the whole growth period was546.22 mm,and it was the largest in jointing and heading period,accounting for26.68% and 23.35% of the whole growth period.Under the barrel experiment,the water demand of spring highland barley in the whole growth period shows the law of "increase decrease".The total water demand of spring highland barley in the whole growth period is 204.48 mm,and the water demand in the jointing and heading period is the largest,accounting for 33.49% and 38.39% of the whole growth period.(4)When the meteorological data are incomplete,the Irmark-Allen method and the modified Priestley-Taylor method can be used to calculate the reference crop evapotranspiration instead of the relatively complex FAO Penman Monteith method in Linzhi,Tibet.(5)Jensen model has good applicability in Linzhi,Tibet.