The Experimental Research On The Interaction Process Of Soil Water Potential And Peach Tree Life

Based on analysis of a large number of research results related to soil moisture and fruit tree growth at home and abroad, this text finds that researches on the control indexes of directly instructing irrigation are relatively weak. At present, many scientists attempt to answer this question by studying the response of plant itself index to moisture and have got certain research results. There are mainly two kinds of indexes reflecting whether the plant has a lack of water under ordinary conditions: one is plant itself physiological and growth index; the other is soil moisture index mainly including soil moisture content and soil water potential. The soil moisture content is greatly influenced by soil texture changes, and therefore the typicality of describing the degree of soil drought is bad. However, the soil water potential can describe the degree of soil drought from energy more effectively and is not directly affected by soil texture changes, and so it has strong typicality and universality.Based on the above ideas, this text takes the peach tree as the object of study to analyze the effect of soil water potential on peach tree life process and fix on the suitable soil water potential within the growth cycle of peach tree. I start the related researches through plot experiment and pot experiment respectively. In the plot experiment, I control the soil water potential within four intervals separately, namely A(-110～-130Kpa), B(natural conditions), C (-10～-20Kpa) and D(-40～-60Kpa); I mainly fix several crucial soil water potential threshold values through pot experiment in the peach tree life process. I have preliminarily obtained some major research results as follows:(1) Analyze the effects of soil water potential on changes of peach tree physiological and growth indexes.The results show that when the soil water potential is kept between -40Kpa and -60Kpa, some physiological indexes of peach tree, such as photosynthesis rate, transpiration rate, leaf water use efficiency and stomatal conductance, etc, are maintained in a higher level, which are favorable for the growth of peach tree.The greatest daily shrinkage of peach tree stem varies with the season and there are greater differences, in winter, the fluctuation range of the greatest daily shrinkage variation is greater, namely approximately between 0μm and 1000μm and in spring, the variation range is smaller than that in winter, however the mutation of air temperature will give rise to a violent reaction of the greatest daily shrinkage of peach tree stem, and therefore I preliminarily judge that the temperature change has greater influence on the greatest daily shrinkage variation of stem. In summer, the normal fluctuation range of the greatest daily shrinkage of peach tree stem is between 50μm and 500μm and in autumn, the variation range is smaller than that in summer, namely about 50μm to 300μm. Meanwhile the analysis shows that for field peach tree, when the soil water potential is lower than -100Kpa, the greatest daily shrinkage of peach tree stem increases noticeably and the soil water potential changes within -100Kpa, which has a small influence on the greatest daily shrinkage of peach tree stem.The variance analysis shows that the peach tree stem growths in the whole growth cycle in different plots have significant differences and the growths in the whole growth cycle are ranged according to size: D>C>A>B. The experimental results show that the soil water potentials between -10Kpa and -20Kpa is not propitious for the growth of peach tree and the soil water potential between -40Kpa and -60Kpa is suitable for its growth.(2)Establish multiple regression mathematical models between ecological factors and peach tree growth.Establish the related mathematical models between daily variation of peach tree stem in every month and 30cm soil water potential (WPs), 5cm soil temperature (Ts5), 15cm soil temperature (Ts15), 30cm soil temperature (Ts30), air temperature(Ta), relative air humidity(RH), net solar radiation Qn and wind velocity and all the multiple correlation coefficients are above 0.9. The results show that in different months, the major factors affecting the daily variation of peach tree stem are different. Analyze the relations between the average daily variation of peach tree stem (ATDV) and 30cm daily average soil temperature (ATs30), daily average temperature (ATa), daily average relative humidity (ARH), daily average net solar radiation (AQn) and daily average wind velocity (AV), establish the multiple regression model and all the multiple correlation coefficients are between 0.8 and 0.9.Establish the multiple regression equation between the stem daily variation in peach tree growth cycle and ecological factors and the multiple correlation coefficient R=0.799; fix the multiple regression equation between the average stem daily variation in peach tree growth cycle and ecological factors under different soil water potential conditions, the multiple correlation coefficient R=0.85; crystallize the relations between the greatest stem daily shrinkage in peach tree growth cycle and ecological factors under different water potential conditions and the multiple correlation coefficients R are between 0.5 and 0.7; meanwhile, I analyze the relations between the stem daily growth in peach tree growth cycle and ecological factors and establish the related regression models.Establish the multiple regression equations between fruit daily growth variation in different months and ecological factors and the multiple correlation coefficients are between 0.6 and 0.9. Fix the multiple regression model between the average daily variation in fruit growth cycle and many ecological factors and the multiple correlation coefficient R=0.792.The research shows that in different periods of time, the major factors affecting the growth of peach tree are different, on the basis of further fixing the degree of correlation between the growth of peach tree and ecological factors, we can adjust and control micro-environmental changes by means of different measures in practice to further increase the peach tree potential productivity.(3) Analyze the characteristics of temporal and spatial variation of soil temperature in various growth periods under different soil water potential conditions.The results show that the daily variations of both 5cm and 15cm soil temperatures in various growth periods handled in different ways are in accord with rules of polynomial change, the daily variation of 30cm soil temperature is in accord with rules of quadratic function; the daily variations of all layers of soil temperatures in the growth cessation period decrease linearly. The emergence times of daily average temperature values and extreme values handled in different ways are different. After having analyzed the characteristics of seasonal variations of the soil temperatures under different soil water potential conditions, the results show that in different seasons, the rules of annual variation of soil temperature are different and the soil moisture has an obvious influence on the soil temperature variation. The rules of annual variations of all layers of soil temperatures conform to rules of quadratic function, the crest value of daily average temperature of 5cm soil appears on the 140th day of the whole year and the maximum temperatures of 15cm and 30cm soils appear on the 200th day. Fix the rules of soil temperature variation in different periods of time to provide the foundation for soil temperature regulation and control in productive practice.(4) Fix the rules of the daily variation of peach tree stem and fruit under different soil water potential conditions.The analysis shows that the processes of daily variation of peach tree stem in various growth periods are in accord with rules of polynomial change. The processes of daily variation of stem in different growth periods are as follows: the variation process in dormancy period: shrinkage- rapid expansion- microshrinkage; the daily variation processes of stem in the three growth periods at the back: expansion- shrinkage- expansion. The daily variation of fruit is also in accord with rules of polynomial change, we can predict the fruit growth trend according to fitted equations and judge whether the growth of fruit is normal.(5) Preliminarily fix several crucial soil water potential threshold values in peach tree life process. Divide the peach tree life process into three life states, namely death status, sub-health status and health status according to the rules of peach tree life variation. Meanwhile define the soil water potential regions divided according to the life states as death water potential, sub-health water potential, suitable water potential and extravagant water potential respectively. The death water potential refers to the lowest soil water potential before condensing when the soil water potential reaches or is less than a certain value, the plant can not restore life phenomenon again under condensing conditions. The suitable water potential refers to the soil water potential which can guarantee the normal growth of plant when the soil water potential reaches a certain value or a certain water potential range and various physiological indexes are in health status. The sub-health water potential refers to the soil water potential which influences the normal growth of peach tree because of moisture stress when the peach tree is in a certain soil water potential range. The extravagant water potential refers to the soil water potential when the soil water potential reaches or is above a certain value, the water use efficiency of plant no longer increases even decreases along with the rise of soil water potential.I make certain that the peach tree may die when the soil water potential is maintained between -957.2Kpa and -2428.1Kpa by shooting and recording the changes of peach tree growth state in the process of water control and analyzing the characteristics of peach tree growth change in the death process. Based on the analysis of the life states corresponding to different soil water potentials, further analyze the relations between the greatest daily shrinkage of peach tree fruit, daily mass growth of fruit and soil water potential changes and fix the upper limit value of peach tree suitable water potential is between -30Kpa and -10Kpa and the lower limit value is between -60Kpa and -40Kpa. On the basis of having fixed the death water potential and suitable water potential, fix the sub-health water potential is between -957.2Kpa and (-60～-40Kpa) and the extravagant water potential is between (-30～-10Kpa) and 0Kpa according to the definitions of sub-health water potential and extravagant water potential.