| Our country is facing increasingly prominent water shortage problem.Shanxi Province,located in the loess plateau to the east,is one of the most water scarcity in China.Drip irrigation technology is a kind of modern water-saving irrigation technology with high water use efficiency,which is 30%-40% higher than that of sprinkler irrigation and 70%-80% higher than that of traditional irrigation.SH short anvil is one of apple dwarf rootstock to adapt to the natural conditions in our country breeded by institute of pomology,Shanxi academy of agricultural sciences.The requirements of the drip irrigation upper limit and lower limit in apple production changes by different tree species,tree age,local factors such as climate and soil structure.To determine the appropriate drip irrigation upper limit and water requirement characteristics of SH short anvil apple trees will contribute to formulating reasonable irrigation systemand further promotion of drip irrigation technology in arid and semi-arid loess plateauregion in SH apple orchards.This paper set up 60% drip irrigation lower limit of field capacity and70%(T1)?80%(T2)?90%(T3)?100%(T4)drip irrigation upper limit and surface irrigation as controlled trials.We collect and analyze the soil moisture content?evaporation between trees?sap flow velocity?leaf water potential in the early morning?new shoot growth?stem diameter?photosynthetic characteristic?leaf water use efficiency ? meteorological factors in month 4-10,2016.By using experimental data,we analyze soil moisture distribution characteristics under the condition of drip irrigation,use stem flow gauge-micro method of evapotranspiration and water balance method to calculate the SH short anvil water requirement characteristics of apple trees,Obtain the physiological indicators of change characteristics and influencing factors and base on principal component analysis synthetically to determine appropriate SH short anvil apple saplings irrigation upper limit.1.The study of SH dwarf apple tree soil moisture distribution characteristics under the condition of drip irrigation.(1)Under different drip irrigation upper limit,the average volume soil moisture content are within the scope of upper and lower limit in the test.On the whole,with the irrigation upper limit rising,time that soil moisture content to rich the lower limit is longer,irrigation frequency is also less.(2)Different irrigation upper limit of soil moisture increment in vertical and radial distribution are basically identical.Increment of soil moisture contentchange in vertical and radial accords with exponential function,the increment of soil moisture content and soil depth,negative correlation between the radial distance.The results showed that different irrigation upper limit soil moisture increment two-dimensional distribution almost the same.Within the scope of different depth,different radial distance,the greater the irrigation upper limit,the greater the soil moisture content volume increment.2.The photosynthesis properties of SH dwarf apple treeunder drip irrigationTo calculate the whole growth period of apple saplings water feature size relations by the stem flow meter-micro evapotranspiration and water balance method,the result shows total water demand relationship T1<T2<T3<T4<CK,intensity of water requirement in the whole stages T1<T2<T3<T4<CK.The calculation results show that with the increase of irrigation upper limit,the total water requirement gradually increases,water demand in different months basically render is June August July May September April October.Two methods of calculating results error is relatively small,so the two methods are available for calculating testbed fruit intensity of water demand and daily water requirement in the whole stages provides guidance and help.3The physiological indexes of SH dwarf apple tree under drip irrigation(1)The leaf water potential in the early morning under different upper limit irrigation and surface irrigation treatment is almost the same,at different times,the leaf water potential average in the early morning of whole growth period T4>T3>CK>T2>T1,the differences between different treatments reached asignificant level(P<0.05),it shows that different irrigation upper limit has significant effects on leaf water potential in the early morning.(2)The new shoots growth ? trunk diameter under different upper limit irrigation has the same change trend,as time increases gradually.Comparing five kinds of treatments comprehensively,the new shoots cumulative growth in five to ten month is CK>T3>T4>T2>T1,the trunk diameter cumulative growth is T3>T4>CK>T2>T1.The two index between different treatments reached a significant level(P<0.05).(3)The new shoots growth ? trunk diameter under different upper limit irrigation basicly meet the Logistic equation,reach a excellent fitting degree.There is a certain gap between model predicted and the measured values,but the error is small,that model accuracy is higher,can well predict the growth of fruit trees.The Logistic growth model can well predict the the new shoots growth?trunk diameter of apple tree and its growth trends.(4)The leaf photosynthetic characteristics index as net photosynthetic rate,stomatal conductance,transpiration rate,intercellular CO2 concentration and leaf water use efficiency under different irrigation upper limit are similar trends.Get these four leaf photosynthetic characteristics index correlated analysising,the tree net photosynthetic rate and intercellular CO2 concentration showed a significant negative correlation;stomatal conductance and transpiration rate and intercellular CO2 concentration appear very significant positive correlation;intercellular CO2 concentration and transpiration rate show significant positivecorrelation.Significant difference was found in leaf net photosynthetic rate between different treatments,comprehensive comparison of five kinds of treatment,90% water-holding capacity irrigation upper limithas the highest leaf water use efficiency.4.Based on principal component analysis method to determine the most suitable irrigation upper limitBased on principal component analysis method to get three principal component factors,the new shoot growth of apple trees and photosynthesis properties index,soil moisture index of apple trees,trunk diameter growth index.The score rank of comprehensive principal component is T3>T4>CK>T2>T1.It states thatcomprehensive considerating leaf water potential in the early morning?growth?photosynthesis properties and water use efficiency of five kinds of treatments,T3 treatment is the most beneficial treatment to young SH dwarf in the local climate conditions.It is concluded that the most suitable irrigation upper limit is 90% water-holding capacity when the lower limit is 60%.This level is most appropriate to the growth of young SH dwarf apple tree in test area. |
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