Effect Of Water Regulation And Intercropping Alfalfa On Soil Moisture And Lycium Barbarum Yield

Aiming at the shortage of water and soil resources in the Yellow River irrigation area of Gansu Province and the low productivity and water use efficiency of Lycium barbarum traditional planting,the water regulation and intercropping planting mode suitable for water saving and yield increase of Lycium barbarum in the Yellow River irrigation area were explored.The field experiment was conducted in Jingtai County of Gansu Province from2019 to 2020 with four water gradients（full irrigation W1,75%-85%;mild deficit W2,65%-75%;moderate deficit W3,55%-65%;severe deficit W4,45%-55%）and two planting patterns（monocropping Lycium barbarum D and alfalfa intercropping Lycium barbarum J）were used to study the effects of water regulation and intercropping alfalfa on soil moisture characteristics,farmland water consumption characteristics,physiological growth,yield and water use efficiency of Lycium barbarum.The mechanism of water regulation and intercropping alfalfa on soil moisture characteristics and crop growth and development of Lycium barbarum was clarified,and the mechanism of water regulation and intercropping alfalfa on water saving,yield increase and income increase of Lycium barbarum was revealed.The study can provide scientific basis for the selection of Lycium barbarum planting mode and water regulation irrigation in Gansu Yellow River irrigation area.The main conclusions are as follows:（1）The average soil water content of 0-60 cm soil layer in the field of Lycium barbarum intercropping alfalfa model was 1.4%～11.8%lower and the surface soil water content was higher than that of Lycium barbarum monoculture.The effect of water regulation on soil water content in farmland was more significant than that of intercropping alfalfa.The 0-40 cm soil layer was the active layer of soil moisture change,and the 80-120cm soil layer was the stable layer of soil moisture change.The soil water consumption of monoculture of Lycium barbarum mainly occurred in about 40 cm soil layer,and the soil water consumption of intercropping alfalfa of Lycium barbarum mainly occurred in about60 cm soil layer.（2）The irrigation amount and total crop water consumption increased first and then decreased with the growth period of Lycium barbarum,and reached the peak at full fruit stage.The irrigation amount and total water consumption of crops decreased with the increase of water deficit.The irrigation amount and total water consumption of alfalfa intercropping were 7.2～71.4%and 3.8～30.8%higher than that of monoculture.The effect of water regulation and rainfall on crop water consumption ratio was significant（P<0.05）,and the effect of intercropping alfalfa on crop water consumption ratio was not significant（P>0.05）.The proportion of irrigation water to total water consumption was negatively correlated with the proportion of rainfall to total water consumption.（3）The diurnal variation of net photosynthetic rate,stomatal conductance and transpiration rate of Lycium barbarum leaves showed a bimodal trend,and"photosynthetic lunch break"appeared at about 14:00.The diurnal variation of intercellular CO₂concentration decreased first and then increased with time.With the increase of water deficit,the daily average net photosynthetic rate and transpiration rate of Lycium barbarum leaves decreased,and the daily average stomatal conductance and intercellular CO₂concentration of intercropping Lycium barbarum increased under mild water deficit.Alfalfa intercropping with Lycium barbarum increased stomatal conductance and intercellular CO₂concentration of Lycium barbarum leaves,and decreased net photosynthetic rate and transpiration rate of leaves.The increase of water deficit and intercropping alfalfa inhibited the growth of Lycium barbarum.（4）Mild deficit irrigation W2 treatment can increase the 100-grain weight of Lycium barbarum,intercropping alfalfa mode under sufficient water condition Lycium barbarum dry weight is larger.The yield of Lycium barbarum decreased with the increase of water deficit,and the yield of Lycium barbarum was reduced by intercropping alfalfa.The highest dry fruit yield was 2749 kg·hm^-2under JW1 treatment in 2020.（5）The irrigation water use efficiency of Lycium barbarum increased with the aggravation of water deficit,and the water use efficiency increased first and then decreased with the aggravation of water deficit.The water use efficiency of Lycium barbarum with mild deficit was 3.97 kg·hm^-2·mm^-1.Intercropping alfalfa reduced irrigation water use efficiency and water use efficiency of Lycium barbarum,the maximum were 6.88kg·hm^-2·mm^-1and 3.55 kg·hm^-2·mm^-1,respectively.However,due to the output of alfalfa,crop irrigation water use efficiency and water use efficiency can reach 71.24 kg·hm^-2·mm^-1and 29.10 kg·hm^-2·mm^-1,respectively.