| Xanthoceras sorbifolia planting is an important economic industry in Hexi Corridor,but soil salinization and water shortage seriously limit the development of local agricultural economy.Surface irrigation has been used to leach soil salinity for a long time,and this longterm unscientific irrigation method leads to soil secondary salinization and waste of water resources.In this study,the effects of different soil matric potential(SMP)thresholds on soil water,salt and fertilizer transport characteristics,crop growth,yield and water use efficiency in Xanthoceras sorbifolia orchards under drip irrigation were studied in order to provide scientific basis for the formulation of drip irrigation system for Xanthoceras sorbifolia in this area.The field experiment was carried out in Zhangye City,Gansu Province(central area of Hexi Corridor)from 2021 to 2022.The young tree stage(1-year-old)and fruiting stage(5-year-old)Xanthoceras sorbifolia fruit trees were selected,and the traditional surface irrigation was used as the control.Different SMP threshold treatments were set under drip irrigation conditions.The young tree stage was-10,-20,-30,-40 kPa and-50 kPa,and the fruiting stage was-5,-10,-15,-20 kPa and-25 kPa.The soil physical properties(matric potential,bulk density and water),chemical properties(pH,ECe and nitrate nitrogen content),growth index(plant height,ground diameter,etc.)and yield of Xanthoceras sorbifolia were measured.The effects of different SMP threshold drip irrigation on soil physical and chemical properties,crop growth and yield were studied.The main conclusions are as follows :(1)In two years,drip irrigation based on SMP threshold can effectively increase the soil volumetric water content in 0-100 cm soil layer,especially in 0-40 cm soil layer,and improve the soil water environment in crop root zone.The soil volumetric water content increased with the increase of SMP threshold,and the increase of soil water content in root zone was greater than that in 0-100 cm soil layer.Surface irrigation treatment could not guarantee the water supply in the root zone of crops.For Xanthoceras sorbifolia at the young tree stage,the soil moisture content in the root zone could not be maintained within the range that did not affect the normal growth of crops under-40 kPa and-50 kPa treatments.All drip irrigation treatments of Xanthoceras sorbifolia at the fruiting stage could keep the soil moisture content in the root zone within the drought tolerance limit of crops.(2)Based on the two years of irrigation and leaching,drip irrigation based on SMP threshold can effectively reduce the overall ECe of soil,which is conducive to improving the salt and nutrient status of crop root zone.The average ECe of 0-100 cm soil layer at the end of 2022 growing season under the highest SMP threshold of-10 kPa and-5 kPa at sapling stage and fruiting stage was 4.03 d S/m and 4.32 d S/m,respectively,which was 30.96% and43.18% lower than that before the experiment.The average ECe values of the root zone soil were 2.60 d S/m and 3.31 d S/m,respectively,which were 51.32% and 57.91% lower than those before the experiment.The root zone soil ECe can be reduced to a range that does not affect crop growth;the content of soil inorganic nitrogen(nitrate nitrogen and amine nitrogen)in the root zone of drip irrigation treatment was significantly higher than that before the experiment.(3)Appropriate SMP threshold drip irrigation can significantly improve the plant height,stem,yield and water use efficiency of Xanthoceras sorbifolia.For the sapling stage of Xanthoceras sorbifolia,the plant height and ground diameter growth of-30 kPa treatment were the highest;compared with the surface irrigation treatment,the yield of the treatments from-5 kPa to-25 kPa increased by 18.86%,29.54%,37.99%,37.60%and31.55%,respectively,and the water use efficiency increased by 81.38%,113.67%,170.78%,189.82%and188.95%,respectively.The yield of-15 kPa treatment increased the most,and the water use efficiency of-20 kPa treatment was the highest.In summary,in the planting of Xanthoceras sorbifolia in the Hexi Corridor region,a negative pressure meter can be installed at a depth of 20 cm directly below the emitter to monitor soil moisture and guide drip irrigation according to SMP.Considering the physical and chemical properties of soil in growing season,salt tolerance and drought tolerance of Xanthoceras sorbifolia Bunge,growth,yield and water use efficiency of Xanthoceras sorbifolia Bunge,it is suggested that the SMP threshold of drip irrigation control of Xanthoceras sorbifolia Bunge is-30 kPa in young tree stage and-20 kPa in fruiting stage. |
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