| The shortage of water resources and the traditional flood irrigation method in Hexi Oasis cool irrigation area seriously restrict the sustainable development of agriculture in this area.In order to break through the bottleneck,the goal of water saving,stable yield and quality improvement of crops in this area can be achieved by introducing drip regulated deficit irrigation under film mode.This study was conducted at the Yimin Irrigation Experimental Station of the Hongshuihe Management Office of Minle County,Zhangye,Gansu Province from April to October in 2019 and 2020.The tested material variety was"Qingshu 168".According to the different growth stages of potato and the"Irrigation Experiment Specification"（SL13-2015）,a total of 8 regulated deficit irrigation treatments and 1 full irrigation control were designed,which were:regulated deficit irrigation at seedling stage（WD1,55%-65%of Field Capacity（FC）;WD5,45%-55%FC）,tuber initiation stage regulated deficit irrigation（WD2,55%-65%FC;WD6,45%-55%FC）,tuber bulking stage regulated deficit irrigation（WD3,55%-65%FC;WD7,45%-55%FC）,starch accumulation stage regulated deficit irrigation（WD4,55%-65%FC;WD8,45%-55%FC）and full irrigation during the whole growth period（CK,65%-75%FC）.The dynamic change law of soil moisture,temperature,nutrients,microorganisms and enzyme activities in potato soil under film drip irrigation in different growth periods was analyzed,and the effect of water deficit adjustment on potato growth physiological characteristics,yield and quality was studied.Combined with Jensen,Minhas,Blank,Stewart four functions to explore the water production model in line with the potato cultivation management in this area,and finally used the AHP combined with the fuzzy mathematics comprehensive evaluation method to screen the optimal irrigation system for potatoes.The results of the study were as follows:（1）The average annual water consumption in the tuber bulking stage was the largest,reaching 185.35～239.52 mm,followed by the average annual water consumption in the tuber initiation stage and starch accumulation stage,which were100.02～132.30 mm and 82.48～112.36 mm respectively,and the average annual water consumption in the seedling stage was the least,49.32～69.81mm.Water consumption intensity and water consumption modulus showed similar trends,tuber bulking stage>tuber initiation stage>starch accumulation stage>seedling stage.（2）The drip irrigation under film has obvious effects on temperature increase and moisture preservation,and effectively regulates the soil water and heat conditions.At the seedling stage,the soil temperature of the WD1 and WD5 treatments was higher than that of the control treatment,and the soil temperature rising rate was higher than that of the control CK,which was beneficial to the germination of tubers;from the tuber initiation stage to the tuber bulking stage,the soil temperature of each soil layer in the treatments of WD2,WD3,WD6 and WD7 was higher than that of CK;during the starch accumulation period,with the fall of the outside atmospheric temperature,the soil temperature also gradually fell,but under the influence of water stress,the soil temperature of the WD4 and WD8 treatments was higher than that of the control,which prolonged the reproductive growth cycle of potato.（3）Water stress changed the soil nutrient consumption of potato.The consumption of alkaline hydrolysis nitrogen was the largest in WD1 treatment,reaching 23.59 mg·kg-1,followed by WD4,and the least consumption in WD6treatment,which were 21.68 and 4.59 mg·kg-1 respectively;available phosphorus consumption and available potassium consumption showed the order of WD1>CK>WD4>WD2>WD8>WD5>WD3>WD7>WD6;at the same time,the numbers of bacteria,fungi and actinomycetes gradually decreased with the deepening of the soil layer,he numbers of bacteria and actinomycetes in the water stress treatment during the whole growth period of potato were lower than those of the control,and the water stress effect was the most significant in the tuber bulking period;the effect of water stress on the number of fungi was absolutely opposite to that of bacteria and actinomycetes,and the specific performance was mild water stress>moderate water stress>control.The activities of urease and sucrase in mild water stress were higher than those in the control,while those in moderate water stress were lower than those in the control;the activities of catalase and alkaline phosphatase were higher than those in the control under water stress.（4）The mild water deficit adjustment treatment at the seedling stage had no significant effect on the net photosynthetic rate of potato.Although the moderate water deficit adjustment treatment would reduce the potato net photosynthetic rate,it had a compensatory effect after rehydration.With the passage of growth period,the net photosynthetic rate,stomatal conductance and transpiration rate of WD2,WD3,WD4,WD6,WD7,and WD8 treatment decreased respectively compared with the control（10.22%,8.72%,11.44%,19.55%,15.89%,23.53%）,（17.12%,24.61%,14.25%,32.43%,33.65%,19.88%）,（9.38%,13.26%,18.19%,13.60%,24.50%,10.23%）,and the intercellular CO2 concentration and leaf water use efficiency increased（6.85%-37.24%）and（9.57%-31.40%）respectively at this stage.Meanwhile,the tuber initiation stage and tuber bulking stage were the peak water use period of potato that were most sensitive to water stress.Water stress at this stage will significantly affect its photosynthesis,which will lead to the final reduction of crop yield.（5）Mild deficit adjustment at seedling stage had no significant effect on potato growth dynamics,but the root-shoot ratio of WD1 and WD5 increased respectively by42.33%and 84.52%,compared with the control.From the tuber initiation stage to the starch accumulation stage,the potato plant height（1.03%～34.59%）,stem diameter（5.45%～28.23%）,leaf area（9.90%～55.80%）,the formation of dry matter accumulation per plant（7.35%～24.66%）and the distribution of dry matter were reduced while increasing the root-shoot ratio of potato.And the degree of influence increases with the degree of regulation deficit,so it was not suitable for water deficit regulation in all growth stages except the seedling stage.（6）Mild water deficit WD1 treatment at seedling stage had no significant effect on its yield and yield components compared with the control;from the tuber initiation stage to the tuber bulking stage,water stress had an obvious effect on the number of tubers per plant,the weight of tubers per plant,and the longitudinal and transverse diameters of potatoes.During the starch accumulation period,there was no significant difference between the mild regulated deficit irrigation and the control,while the moderate water stress still obviously decreased the potato yield compared with the control.Simultaneously,the average annual yield of potatoes in the treatment of WD1was the highest,reaching 47766.96 kg·hm-2,followed by CK,which was 43707.6kg·hm-2,and the yield of WD6 was the smallest in the treatment of moderate water deficit during tuber initiation,which was only 35721.25 kg·hm-2.And,the water use efficiency also showed similar changes,the water use efficiency of WD1 was the highest(9.10 kg·m-3),followed by CK(8.20 kg·m-3),and WD6 was the lowest(7.10kg·m-3).（7）Mild water deficit regulation at seedling stage could promote the increase of potato total sugar（0.64%～0.77%）,protein(2.22 mg·g-1～2.48 mg·g-1)and starch content accumulation（39.87%～45.77%）,but had a significant inhibitory effect on vitamin C accumulation;from the tuber initiation stage to the starch accumulation stage,water stress was not conducive to the accumulation of potato total sugar,protein and starch content,and the water stress was most significant in the tuber bulking stage,but it had a promoting effect on the formation of vitamin C content.Among them,the total sugar content and starch content of WD1 treatment were the highest,0.73%,45.08%,respectively;the protein content of WD5 treatment was the highest,which was 2.45 mg·g-1,and the vitamin C content of WD8 treatment was the highest,22.83 mg·100g-1.（8）Through the fitting of the four models of Jensen,Minhas,Blank and Stewart,it was found that the fitting degree of the Jensen model and the Stewart model was good,and the water shortage sensitivity index was in the order of tuber bulking stage>tuber initiation stage>seedling stage>starch accumulation stage.Based on the combination of analytic hierarchy process（AHP）and fuzzy comprehensive evaluation,it is found from the comprehensive evaluation of economic benefit,quality,water consumption and environmental benefit of potato drip regulated deficit irrigation under film mode in Hexi Oasis cool irrigation area,WD1treatment（55%-65%of field water capacity）was the optimal irrigation mode.Based on the comprehensive indexes of potato yield,quality,water consumption and nutrient consumption,the optimal irrigation strategy for potatoes in Hexi oasis cool irrigation area was water deficit adjustment at seedling stage（soil relative water content was 55%-65%of field water capacity）and full irrigation at other growth stages（soil relative water content was 65%-75%of field water capacity）. |
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