Stady On Water Use Source And Strategy Of Lycium Barbarum In Inland River Source-Irrigation Areas

The northwest inland river irrigation area is rich in light and heat resources and is an important high-quality wolfberry?Lycium barbarum?production area in China.However,the contradiction between supply and demand of water resources in this area is outstanding.The drought and lack of water seriously limit the wolfberry high-quality sustainable development in this area.Therefore,it is necessary to ascertain the water use characteristics of wolfberry during the growing period,provide information to develop formulate the best field water management measures and irrigation strategies,and achieve efficient use of water resources.In this study,the main crop wolfberry in the Huaitou Tala Irrigation district in Qaidam Basin,Qinghai Province was as the research target.Three management measures were set up:bare soil with flat planting?CK?,mulching with flat planting?MF?,and mulching with ridge-furrowing?MR?.Using stable hydrogen and oxygen isotope technology,the changes of water use in the growth period of wolfberry provide a reference for the wolfberry planting model in the northwest inland irrigation area,and the results show that:?1?There are show significantly discrepancy in the spatial and temporal distribution of soil water content in wolfberry fields under different management modes.The soil water content increased and decreased hereafter in all treatments.The shallow soil water content changed most drasticly,but the soil water content in CK was significantly lower than that in MF and MR.MR>MF>CK total fine root length density.Under three kinds of management models,the fine root length density of each layer in the field of wolfberry decreases with increasing soil depth.At the same time,the fine root length density is concentrated in the 0-60cm soil layer.?2?The soil water stable hydrogen and oxygen isotope composition of wolfberry field gradually decreases with increasing depth.The range of the stable hydrogen and oxygen isotope composition in the shallow layer?0-20 cm?has the largest variation,the fluctuation of the stable water and hydrogen isotope composition in the middle layer?20-60 cm?is small,and Soil water stable hydrogen and oxygen isotope composition fluctuations tend to stabilize in the deep layer?60-100 cm?.The isotope value of xylem water of wolfberry under 3 kinds of management modes changes with the sampling date.Most of the stable hydrogen and oxygen isotope values of wolfberry xylem under 3 kinds of management modes are not in the soil-plant mixed area-show that it may exist the phenomenon of stable hydrogen isotope fractionation.?3?Through comparative analysis of the three methods,The Iso Source model shows big deviation due to this model does not take into account the spatial differences in the isotopic composition of potential water sources.The MixSIR model is in some cases,the following calculation results are not as accurate as the Iso Source model and the MixSIAR model.Comprehensive evaluation shows that the MixSIAR model has the best prediction effect.The stable hydrogen isotope fractionation of wolfberry during root water uptake may misjudge the utilization ratio of wolfberry to various water sources.SW-excess?The degree of deviation of xylem water?D and its corresponding soil water line?D?can well correct the effect of stable hydrogen isotope fractionation.When the isotopic values of different water sources are greatly different,It is recommended to use M-O mode(?¹⁸O alone)calculation,Otherwise it is recommended to use M-OSD mode(SW-excess modified?D and?¹⁸O dual isotopes)calculation.The isotopic values of different water sources were quite different in this study.The calculation results of MixSIAR model under M-O mode were used to analyze the wolfberry water sources use under different management modes.?4?The results of MixSIAR under the M-O model show that there are great discrepancy in soil water utilization strategies of wolfberry at different growth stages under three management models.The main water sources of MR can constantly changing.During the germination and leaf expansion period,as the air temperature rises and the wolfberry biomass increases,and the wolfberry main water sources slowly turned to the medium-deep layers?20-100 cm?in each treatment;during the flowering fruit-bearing and fruit ripening periods,the CK mainly used relatively stable medium-deep layers?20-100 cm?water sources,and the MF tended to use shallow-medium layers?0-60 cm?water sources,MR can continuously switch between the three water sources;each treatment in the deciduous stage mainly uses medium-deep layers?20-100 cm?water sources.The soil water use pattern of wolfberry is greatly affected by soil water conditions and root distribution.Ridge and mulch measures can significantly improve soil water environment and increase root biomass,which in turn affects wolfberry use of soil water resources.In summary.The MR wolfberry can flexibly use different soil water sources,which is more conducive to the stable growth of wolfberry.The ridge-furrowing combined mulching method is the best planting mode of wolfberry in the arid area.Meanwhile,this area is developing an underground irrigation system due to the large ineffective evaporation.The main water-absorbing layer provides technical support for the design of underground irrigation systems.