Water Consumption Characteristics And Irrigation Schedule Of Mountain Apple Tree Of Surge-Root Irrigation In Loess Hilly-gullied Area Of Northern Shaanxi

Loess Plateau region faces the current situation of long-term drought,unevenly distributed water resources and serious soil erosion.To ensure the sustainable utilization of water resources and improve the economic benefit of ecological economic forests in northern Shaanxi,this paper takes the mountainous apple trees in northern Shaanxi as the research object.The regulated deficit irrigation test was conducted on apple trees under the technical condition of surge-root irrigation in Qingshuigou Ecological Park,Zizhou County,Yulin City,Shaanxi Province from March to November 2017.Different degrees of water deficit treatments were set at different growth periods of apple trees according to the rapidly expanding development scale of the apple industry in Shaanxi Province.In addition,this paper studied the water coumption law of apple trees and the physiological characteristics and yield change of apple trees under the condition of water deficit,and developed the most suitable irrigation system for apple trees in the mountainous regions of northern Shaanxi,through obtaining the data of meteorological data,soil water content and growth development status of apple trees.Main achievements were:(1)After the adoption of the irrigation technique of surge-root irrigation,soil water content reached the maximum value when the vertical height of soil layer was about 40 cm;the decreasing rate of soil water content was the most significant when soil depth was 72 cm;soil water contents decreased with the aggravation of regulaited deficit degree in the position of the same soil depth.During the whole growth period,the variation coefficient of soil water content reduced with the deepening of soil layer.Under regulated deficit irrigation during the same growth period,the variation coefficient of water content of the same soil layer within the scope of 0 cm to 80 cm decreased with the increase of water content;the law was the opposite within the scope of 90 cm to 140 cm.(2)Reference crop evapotranspiration ET0 presented the trend of "high in the middle and low at both ends" during the whole growth period;ET0 reached a peak value during the blossom and fruit period.Partial correlation analysis was conducted to find that ET0 had a significantly positive correlation with sunshine duration and wind speed and was negatively correlated with water vapor pressure during various growth periods.At various growth periods of apple trees,the water consumption of fruit swelling period reached the maximum value.Under full irrigation treatment,blossom and fruit period and fruit swelling period showed high intensities of water consumption,which were greater than 4.2 mm/d.Water deficit level was negatively correlated with the intensity of water consumption.The mean values of crop coefficients of apple trees during various growth periods were fruit swelling period,blossom and fruit period,germination period and fruit ripening period in descending order.Crop coefficient and leaf area index presented a quadratic relationship.(3)The higher soil water content was,the longer duration would be.Larger new-tip length,leaf weight,leaf area,leaf water content and leaf water holding capacity would have no significant influence on new-tip diameter.However,growth amounts during the germination period took up the largest proportions,which were greater than 41%.In the case of mild regulated deficit during the blossom and fruit period,blossom and fruit setting rate obtained the maximum value,namely 59.21%.The leaf area index of apple trees grew rapidly from the end of May to early July.During this period,the growth amount of leaf area index varied from 0.76 to 0.95.The higher soil water content was,the earlier fruit would enter the rapid growth period.Fruit volume was very small when soil water content was at a relatively low level during the fruit swelling period.The staining degree of apples and regulated deficit degree of water were not significant.Single fruit weight showed a positive correlation with soil water content.Fruit firmness displayed the opposite law.During the fruit swelling period,excellent fruit rates were less than 50%under regulated deficit treatment.Fruit water content had a significant positive correlation with soil water content.Low water content could improve the content of soluble solids.The yield witnessed a remarkable increase under surge-root irrigation treatment.Water deficit during the germination period had no significant influence on yield.During the blossom and fruit period,apple yield was at a high level under mild and moderate regulated deficit treatments.Soil water was controlled at a relatively low level during the fruit swelling period,which led to an obvious reduction in yield.During the whole growth period of apple trees,water consumption and yield presented a downward quadratic relationship.Yield reached a peak value when water consumption was 730 mm.During the fruit swelling period,water sensitivity was high.During the blossom and fruit period,net earning achieved the highest,namely 331,500 yuan/hm2 under mild deficit treatment.(4)This paper established an evaluation system for the irrigation system of apple trees of surge-root irrigation in the mountainous regions of Shaanxi and conducted a comprehensive analysis on fruit quality,yield,water use efficiency and economic benefit.Meanwhile,it pointed out that the number of times of irrigation at germination period,blossom and fruit period,and fruit swelling period were 1,1 and 4 respectively,which was the most suitable efficient water-saving irrigation system of apple trees in the rainy years of northern Shaanxi.Irrigation was not carried out during the fruit ripening period.Irrigation quota was 930.5 m3/hm2.