| Apple tree is one of the main varieties planted in the Loess Plateau of China.It has high economic value and is a plant with large water demand.However,due to the perennial drought in this region,rainfall distribution is uneven,water supply and demand contradiction is serious,affecting the economic development.Therefore,according to local conditions,professor sun xi huan introduced the water storage pit irrigation method,which has the characteristics of saving water,retaining water and resisting drought.As an important process of physiological characteristics of apple trees,transpiration consumes a lot of water.Therefore,the study of transpiration characteristics of apple trees under water pit irrigation can provide a theoretical basis for the study of crop water demand and the establishment of irrigation system,which is of great significance for the economic development of this region.Under field conditions,this paper,with 10 years of growth of dwarfing ChangfuⅡtype Red Fuji apple trees treated as materials,studied the effect of different irrigation upper and lower limits（water storage pit irrigationT1:80%and 60%of field water capacity,T2:90%and 70%of field water capacity,T3:100%and 80%of field water capacity;T4:100%and 60%of field water capacity,control treatment of ground irrigation,CK:80%and 60%of field water capacity）on Transpiration Characteristics of Apple Trees at Leaf Scale and Single Tree Scale,aiming to provide a scientific basis for the more accurate estimation of apple tree irrigation quota in this region,and also providing a theoretical basis for the comprehensive management of stand waters in this region.The main conclusions of this paper are as follows:1.Effects of different irrigation upper and lower limits on soil water spatial and temporal distribution under water storage pit irrigation（1）The average soil moisture content in the planned wetting layer under different treatments all changes dynamically within the range of upper and lower limits of irrigation set by the test.The higher the upper and lower limits of irrigation,the more irrigation water,the higher the soil moisture content.（2）The vertical distribution characteristics of soil moisture content under different treatments are basically the same,showing a change trend of increasing and then decreasing with the increase of soil depth.However,the depth of the maximum value of soil moisture content is different.The maximum value of soil moisture content in water storage pit irrigation was about 80cm from the surface,which was twice the depth of water storage pit.However,the maximum moisture content of CK in surface irrigation treatment occurs shallowly,about40cm from the surface.2.Effects of different irrigation upper and lower limits on transpiration characteristics of apple trees with different leaf sizes under water storage pit irrigation（1）The daily variation trend of transpiration rate of apple leaves under different treatments was similar,showing a single-peak curve,and the peak time appeared from 11:00 to 13:00.The daily average transpiration rate of leaves in water storage pit irrigation treatment T3 was always the maximum value in each treatment,while T1 was always the minimum value,and there was a significant difference between them.The average daily transpiration rate of the leaves treated with T2 and T4 was in the middle level.Except on May 29,the daily average transpiration rate of leaves in water storage pit irrigation treatment T4was higher than that in surface irrigation control CK.（2）There was a significant positive correlation between transpiration rate of apple leaves and soil moisture content.The daily change of transpiration rate of leaves under different treatments was positively correlated with the daily change of stomatal conductance,leaf surface temperature and atmospheric temperature,and negatively correlated with the intercellular CO2 concentration.With more irrigation water in pit irrigation treatment,the stomatal conductance of leaves has less limitation on transpiration.（3）The monthly variation characteristics of transpiration rate of apple tree leaves under different treatments were basically the same,showing an obvious uni-peak pattern,in which July was the peak of each treatment.The magnitude of annual variation was ranked as T4>T3>T2>CK>T1,and the magnitude of annual average transpiration rate was ranked as T3>T4>T2>CK>T1.Under the condition of pit irrigation,the average annual transpiration rate of apple tree leaves increased with more irrigation water.（4）The monthly change of net photosynthetic rate of apple tree leaves under different irrigation treatments presented a parabolic pattern with downward opening.The average annual value of net photosynthetic rate of leaves under different treatments was ranked as T3>T2>T4>CK>T1.The monthly variation characteristic curve of water use efficiency of apple tree leaves under different irrigation treatments was a parabolic curve with an upward opening.The annual average value of wue of leaves under each treatment was ranked as T2>T4>T1>T3>CK.3.Effects of different irrigation upper and lower limits on transpiration characteristics of apple trees of single tree scale under water storage pit irrigation（1）The diurnal variation characteristics of stem flow rate of apple trees under different irrigation treatments were basically similar,showing obvious diurnal variation rules and roughly taking the shape of"几".From May to September,the daily mean value of stem flow rate under T1 treatment was the minimum value of all treatments,while T3 treatment was the maximum value,and the remaining treatments were at the intermediate level.（2）The monthly variation characteristics of apple tree stem flow rate under different irrigation treatments were basically the same,showing a trend of single-peak curve,and the peak appeared in June.The order of magnitude of annual average stem flow rate was T3>T4>T2>CK>T1.Under the condition of pit irrigation,the more irrigation water,the greater annual stem flow rate of apple trees.The stem flow rate of T3 treated by water storage pit irrigation was significantly higher than that of other treatments throughout the year.T1 was significantly smaller than other treatments throughout the year.The average annual stem flow rate of T3 was 44.4%,14.7%and 11.8%higher than that of T1,T2 and T4,respectively.The average annual stem-flow rate of water storage pit irrigation（T4）was about 8.9%higher than that of surface irrigation（CK）.（3）The diurnal variation of stem flow rate of apple trees was significantly positively correlated with the diurnal variation of solar radiation,atmospheric temperature and wind speed,while significantly negatively correlated with the diurnal variation of atmospheric relative humidity.（4）In sunny days,the daily transpiration and water consumption intensity of apple trees in each treatment of water storage pit irrigation in July was the highest,and the daily transpiration and water consumption intensity of T3 was always extremely significantly higher than T1.Under the condition of pit irrigation,the more irrigation water,the more transpiration water consumption.Under the same irrigation conditions,water consumption of apple trees under water storage pit irrigation was higher than that under surface irrigation.（5）The yield of apple trees treated with pit irrigation T2 was the highest,with 30.51kg/plant,which was about 100.9%,5.5%,29.1%and 65.3%higher than those treated with T1,T3,T4 and CK,respectively.Under the condition of water storage pit irrigation,the more water was irrigated,the more apple trees yielded.Pit irrigation significantly improved apple tree yields compared with surface irrigation.4.The diurnal variation trend of transpiration rate of apple leaves and stem flow rate in growth period was similar,and the correlation coefficient was 0.754at 0.01 level.5.Under pit irrigation,the annual average leaf water use efficiency and irrigation water use efficiency of apple trees treated with T2 were the highest,and significantly higher than those treated with T1,T3 and T4.Although the annual average leaf water use efficiency and irrigation water use efficiency of storage pit irrigation treatment T4 were higher than CK of surface irrigation control treatment,there was no significant difference.Therefore,the water-saving effect of T2 treatment was optimal. |
