The Response Of Jujube Physical Growth To Soil Water On Loess Region In Yulin

Based on the analysis for the present status and existing problems of relative research in home and abroad, the soil properties, stem diameter micro-change, canopy structure, leaf physiological, photosynthetic production and other growth and physiological indexes of four years old pear jujube trees were invesstigated in this paper under four soil moisture treatments, namely T1(-41～-51kPa), T2(-68～-84kPa), T3(-96～-135kPa) and T4(-311～fruit wilting～-311kPa) in jujube water-saving demonstration base located on Loess Plateau. Meanwhile meteorological environment for cultivation and principal meteorological factors influencing stem diameter were studied. At last, water optimal control theory of jujube cultivation were summarized by analyzing the quantitative relations and inner link of indexes for each interface of soil-plant-atmosphere continuum. The preliminary conclusions are were as followed:(1) The meteorological environment had advantages and disadvantages for Jujube cultivation in Northern shaan xi, where solar radiation value was high and radiated time was long and daily average Rs was 226.80wat/m2 during the experimental period. Long time and high value of solar radiation played an important role on the fruit coloring and maturity in the later period. Daily temperature difference(DTD) value is high during experiment period and the daily average value was 13.88℃, which was helpful for improving fruit quality. In study area, the average daily rainfall was 1.71mm, average daily reference crop evapotranspiration was 6.77mm, cultivation environment was relatively dry, rainfall time was continuous, and vapour pressure deficit value and temperature were high from 160 days to 220 days. Fruit expanding period, leaf expansion and flowering period were the main water deficit period, and reasonable irrigation was needed to ensure healthy growth of jujube trees in this time. (2)Daily stem diameter change could be divided into recovery type, deficit type and special type. Daily diameter increase (DI) of recovery type was positive, and deficit type was negative, while the special type has no clear DI. Dynamic change of stem diameter has a negative similar trend with air temperature and a positive similar trend with air relative humidity. MXTD usually appearred about 8 o'clock in the morning, and MNTD usually appearred about 3 o'clock in the afternoon.(3) Rs and Tmd were considered as the main decision variables influencing MDS, and ET0 was the main limiting variables by analyzing the path between MDS and meteorological factors. Transpiration intensity and radiation were thought as the main factors influencing MDS. There were some other factors influencing MDS for the error term value of direct path coefficients and decision-making coefficient were high.(4) daily dynamic of jujube stem diameter and growth rate during the growing season were closely related to soil moisture. The dynamic change of pear jujube stem microvariation was stable in high water treatment plot, while the value was lower than the that under low water treatment. The time of stem from the rapid growth to slow growth was later and the turning point was also lagged behind compared with that under low water treatment. So irrigation could extended the growth time. The stem was thick under low water treatment. Growth Changes of stem diameter could be well fitted by Slogistic1 curve equation.(5) LAI was positively correlated with the soil moisture content, while light transmittance of canopy and tree height were negative correlated with the soil moisture content. Light transmittance of canopy under medium water treatment was in suitable scope of 25% to 35% for a long time, which could make full use of the light energy and not cause orchard canopy closure. Water treatment had an important influence on the Chlorophyll relative content, stomatal limitation, and Ci. Chlorophyll relative content. Stomatal limitation value of pear Jujube leaf was low, while the value of cond and Ci was high in high water treatment plot. Chlorophyll relative content was down when rehydration, but the decreased degree was different to different water stress degree. Net photosynthetic rate and transpiration rate increased with the soil moisture content, but water use efficiency dropped. Irrigation can raised The value of fruit setting rate, fruit retention rate, fruit setting branches and fruit number could be increased significantly by irrigation, meanwhile the total branches number, average fruit number of fruit setting branches and rate of fruit setting branches were also enhanced, but the effect were not remarkable. Proper irrigation could significantly improve fruit weight and total production, but if the water was too much, jujube tree's growth would be affected by flooding stress, and fruit weight and total production would be reduced.(6)Appropriate soil water potential irrigation range of Jujube was from - 68 to - 84kpa, relative to the field capacity from 60% to 65%; Suitable periods for irrigation were flowering and fruit bearing periods and fruit expanding period; Preferred water deficit sensitivity indexes were stem diameter micro-changes (MDS, MXTD, MNTD), and stomatal conductance, and net photosynthesis rate, and transpiration rate.