| The southern foothills of Taihang Mountains are a typical arid and semi-arid climate region,where the uneven spatial and temporal distribution of precipitation and water shortage restrict the sustainable development of agriculture and forestry.Jiyuan,located at the southern foot of Taihang Mountains,is an important node city in the Yellow River basin and plays an important role in the ecological security of the Yellow River basin.Therefore,it is of great significance to study the water consumption pattern of Juglans regia L.in this region to scientifically guide scientific irrigation of walnut,helping the local people to get rid of poverty and become rich,and improving the local ecological environment even in the middle reaches of the Yellow River.In this paper,we investigated the characteristics of trunk water consumption,physiological growth,water use efficiency,and yield quality of Juglans regia L.under four water treatments:60%(T1),80%(T2),100%(T3),and no irrigation(CK),taking 7-year walnut as the test object,in order to provide a theoretical basis for scientific guidance of walnut water management.The main results of the study are as follows:(1)The sap flow rate of walnut with T1(60%soil moisture holding capacity)under sunny days showed a single-peak curve,while the rest of the treatments showed a double-peaked curve.The sap flow rate of walnut showed "single-peak" trend in different treatments on rainy days,and the peak value was smaller than that on sunny days.The maximum and minimum of sap flow rate of walnut was found at the T1 treatment and CK,respectively.Water consumption of walnuts under different moisture treatments during the growth period were:CK(877.08 L)<T3(898.65 L)<T2(933.31 L)<T1(1299.53 L).The maximum and minimum of water consumption of walnuts were found at the fruit expansion stage and maturation period,respectively.The water consumption order under 4 water treatments at the fruit expansion stage and maturation period was CK<T3<T2<T1.Extremely significant difference was found between T1 treatment and other treatments(P<0.01).The maximum of sap flow rate and water consumption of walnut were found during T1 treatment,which indicated that T1 was suitable soil water condition from the perspective of water saving.The meteorological factors affecting the water consumption of walnut were consistent under different water treatments.Air temperature was the key meteorological factor on hourly time scale,and solar radiation was found to be the prominent meteorological factor on daily time scale and phenological period.Solar radiation was testified to the main meteorological factor with the increase of time scale.(2)LAI,SPAD,new shoot length and net photosynthetic rate increased with increasing soil moisture,however,soil moisture above the T2 level inhibits its growth and increases,that LAI(1.88),SPAD(45.06),neonatal length(46.1 mm),and net photosynthetic rate(14.38μmol·m-2·s-1)were greatest at T2 levels of soil moisture,extremely significant difference was found between T2 treatment and other treatments(P<0.01).Daily variation in leaf temperature decreases with increasing soil moisture,except at the T1(38.88℃)level,daily variation in leaf temperature and SPAD did not differ significantly(P>0.05)under different water treatments.Fruit transverse and longitudinal diameter,volume,and transpiration rate all increased with increasing soil moisture,with T3 being the largest and CK the smallest,with highly significant effects between the different moisture treatments(P<0.01).(3)The instantaneous water use efficiency of walnuts under different moisture treatments during the growth period were:T3(2.78 μmol·mol-1H2O)<T2(2.99 μmol·mol-1H2O)<CK(3.12 μmol·mol-1H2O)<T1(3.19 μmol·mol-1H2O);Calculation of water use efficiency using carbon isotopes of walnuts under different moisture treatments during the growth period were:T3(4.11 μmol·mol-1H2O)<T2(4.13 μtmol·mol-1H2O)<CK(4.22μmol·mol-1H2O)<T1(4.33 μmol·mol-1H2O);Moisture production and use efficiencyof walnuts under different moisture treatments were:T1(2.70 kg/m3)<T3(2.94 kg/m3)<CK(4.31 kg/m3)<T2(4.92 kg/m3).In summary,it can be seen that walnut water use efficiency was greatest at T1-T2 levels,indicating that walnut has high water saving capacity and high drought tolerance productivity,making it the best soil moisture treatment.(4)The yield of walnuts increased with increasing soil moisture,but after the soil moisture exceeded the T2 level,the yield of walnuts did not increase but caused a reduction,the maximum yield(2531.3 kg/hm2)was achieved at the T2 level;Nut diameter,kernel yield and total protein content increased with increasing soil moisture,soil moisture had the highest values at the T3 level(3.93 cm,50.46%and 19.09%);Shell thickness,single fruit weight,fat content,and soluble protein content reached the maximum with increasing soil moisture up to the T1 level(0.88 mm,12.71 g,69.42%,and 33.02%)and then gradually decreased.In conclusion,soil moisture content at the level of T1～T2(60%～80%of field water holding capacity)can ensure the highest physiological growth index of walnut,maximum water consumption,kernel fat content higher than 66.3%,total protein content higher than 17.9%,the yield of 64.4%～100%of the highest yield in the experiment and maximum water use efficiency,which was the suitable soil moisture range for high yield and quality. |
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