Study On The Lower Limit Of Soil Moisture Of Jujube Trees On Sandy Land In The Arid Zone Of Central Ningxia

In this paper,the young jujube trees in the old sand belt in the central arid zone of Ningxia were taken as the research object.In view of the problem that the lower limit of soil moisture of the old jujube trees in the arid belt in the central arid zone of Ningxia was not clear,on the basis of the optimal crown width of 60cm,Through setting different irrigation upper limits,carrying out field simulation experiments on issues such as unclear soil moisture lower limit,using different depth geometers,time domain reflectometer(TDR),ruler,vernier caliper,oven,earth drill,aluminum box and other experimental instruments,By setting up soil temperature experiments at different depths and different distances inside and outside the greenhouse,observe soil temperature,soil moisture content,jujube tree growth characteristics and other indicators during the test period,and use icon comparison method,difference analysis,regression analysis and other mathematical methods to study The change trend of soil temperature at different depths,the relationship between the temperature inside and outside the shed,the change trend of soil moisture content,and the influence of different irrigation upper limits on the growth characteristics of jujube trees are based on the combination of daily water consumption and moisture content of jujube trees The method of determining the lower limit of soil moisture of jujube tree mainly draws the following conclusions:(1)The change trend of soil temperature under different treatments and different depths in a day is basically the same,and it shows a trend of first rising and then falling in a day.The highest temperature and the lowest temperature of different treatments appear at the time of 16 points and barrels in sand treatment At 4 points of bare planting treatment,the average temperature decreased with the increase of depth in the four treatments,and the whole showed "field pressure(field pressure sand treatment)>barrel pressure(barrel pressure sand treatment)>Tian bare(field bare Ground treatment)>barrel bare(barrel planted bare ground treatment)trend,the coefficient of variation decreases with increasing depth;the use of cooling measures has no effect on the correlation between deep soil temperature,only the shallow layer temperature;The relationship of soil temperature using different margins and different depths is:y=0.72x+7.58,and the model has certain accuracy after testing.(2)For the soil moisture content,with the increase of depth,the moisture content shows an increasing trend,and the extremely poor moisture content shows that the shallow layer(0?20cm)is larger than the deep layer(20?40cm).It can be seen from the average value of soil water content at different irrigation upper limits that with the increase of the crown width,the average value of water content shows a decreasing trend,that is,the water consumption shows an increasing trend.At depths of 0-20 cm and 20-40 cm,the standard deviation and variance are relatively close,indicating that their overall dispersion is close.Except that the water content of individual groups is more than 0.05,most of the water content shows significant differences.(3)During the test period,the new length of jujube tree showed a trend of "budding leaf-growth stage>flowering fruit-setting stage".By fitting the cumulative growth of the new length of each treatment,it is found that the fitting equations are consistent with the quadratic equation,and the fitting effect is better.(4)For the new diameter,as the simulated rainfall increases,the growth rate of the new diameter increases accordingly.By fitting the growth amount of the new diameter with each treatment,it is found that the fitting equations are consistent with the quadratic equation,and the The combined effect is better.(5)It can be seen from the method of jujube tree water consumption and soil moisture content,when the moisture content is less than 3%,the jujube tree will die and will not be revived,and when the moisture content is 3%?5%The jujube tree has a certain amount of water consumption and the jujube tree can be resurrected after rehydration,that is,the lower limit of the soil moisture of the young jujube tree on the sand is 3%?5%.