Responses Of Pear-jujube Trees To Different Soil Water Content At Critical Water Requirement Stage

This paper analyzed the status and results of the research at home and abroad for itsproblems, experiment was done at the pear-jujube water-saving demonstration bases inMizhi County. In this experiment, two water treatments were set to research the soilmoisture dynamics under different water supply and water conditions of4years oldpear-jujube tree in three consecutive years of critical water demand period (flowering fruitset and fruit enlargement period), which reveals jujube water rules in key water demandperiod. The changes of soil properties and growth physiological indexes(such as jujubetree stem diameter, canopy structure etc.) were also monitored under different soil waterpotential treatment conditions. Combined with the meteorological elements, appropriatecultural climate and environment of pear-jujube would be analysised, and the main factorsaffecting stem diameter Minute changes and the amount of water consumptions would beclear. All of these can provide decision indicators and theoretical basis to the water-savingirrigation technologies of precision Irrigation modern. The two water treatments were: T1,soil water potential is controlled within the range of-41~-51kPa (0.233~0.196cm3/cm3);T2, soil water potential is controlled within the range of-311~fruit wilting~-311kPa(0.061~fruit wilting~0.061cm3/cm3) in2010. T1, soil water potential is controlledwithin the range of-41~-51kPa (0.233~0.196cm3/cm3); T2, soil water potential iscontrolled within the range of water stress~-41kPa~arid (water stress~0.233cm3/cm3~arid) in2011. T1, soil water potential is controlled within the range of-41~-68kPa (0.233~0.151cm3/cm3); T2, soil water potential is controlled within the range of-10～-84kPa（0.375～0.123cm3/cm3）in2012. The main conclusions were as following:(1) MXTD curve showed significantly different under different soil moisturetreatments in the critical water demand period of pear-jujube. The lower soil moisture, the greater DG and the faster MXTD growth rate. Irrigation can effectivly promote the growthof stem diameter. Jujube MDS differences significantly with the different soil moisture.water shortage increases jujube MDS to a certain extent. The MDS are greater inflowering and fruit setting period, but smaller in the late of fruit enlargement period, eachprocessing MDS are small. Diurnal variation of pear-jujube stem diameter is influenced bythe growth duration.(2) The research of stem diameter dynamic changes indicators of pear-jujube in threeconsecutive years of flowering fruit set and fruit enlargement period show that thevariation of MTD and MXTD are consistency in each processing, and the growth rate ofthem differences due to different water treatments. This tell us that the MTD and MXTDcan be used as indicators of tree growth, and they has same result on characterization ofboth plants and soil water.(3) The research of water consumption conditions of pear-jujube in three consecutiveyears of flowering fruit set and fruit enlargement period show that the water consumptionincreases with the increase of the amount of soil water supply, the maximum daily waterconsumption of each treatment was appeared in one week after irrigation. Each waterconsumption curve showed an increasing trend in three years, and water consumptionreached the maximum in the the fruit expansion period. The water consumption intensityof flowering and fruit setting period is less than fruit enlargement period.(4) Soil moisture and meteorological factors has a combined effects on the change ofstem diameter indicators, soil moisture influence the sensitivity of jujube MDS to weatherchanges. The jujube tree MDS is most sensitive to the changes of weather in the treatmentwhich water is suitable. For other water treatments, jujube MDS variation consistent with it,but less volatile.(5) In this paper, the path analysis of meteorological factors as well as waterconsumption in full irrigation conditions with the changes of stem diameter tell us: ET0、VPD are positive related with water consumption changes, they are decision variables.ET0、VPD are positive related with MXTD、MDS，in this, ET0is the main decision variablesof MXTD, Water consumption has negative correlation with MDS changes, as the maindecision variable, water consumption has a very significant impact on MDS.Comprehensive analysis: ET0is the main factor to affect the change of stem diameter and water consumption, MDS as the appropriate moisture deficit sensitive indicator of pearjujube, can well characterize the laws of water consumption.(6) The performance of canopy structure indicators (leaf area index, gap fraction, lighttransmission rate) is significantly different under different soil moisture treatments. Mildwater stress in fruit growth period affect canopy structure indicators, and the rehabilitationof irrigation show some compensation effect. Leaf area index, gap fraction and thetransmittance has a good correlation under different treatments, leaf area index has anegatively correlated with gap fraction and light transmittance, while, gap scores positivelycorrelated with light transmission rate.