Spatial And Temporal Distribution Characteristics And Coupling Effects Of Soil Oxygen,Water And Temperature Under Water Storage Pit Irrigation

The water storage pit irrigation method is a kind of middle and deep three-dimensional irrigation method which is suitable for orchards in northern China and has the advantages of water saving and water conservation.In recent years,for water storage pit irrigation method,domestic and foreign scholars have carried out a lot of in-depth research and achieved fruitful results in soil water,heat,gas and root growth.However,under the interaction of soil water,heat and gas,there are few reports on the growth indicators（photosynthesis,root growth）of fruit trees,which need further research.In this paper,field experiment and theoretical analysis were used to set up three irrigation treatments:W_50-80%,W_60-90%and W_70-100%,with surface irrigation（CK）as the control.The soil water content was controlled at 50%-80%,60%-90%and 70%-100%of the field capacity respectively.The spatial and temporal distribution of water,heat and air in orchard soil and their coupling effects on Photosynthesis and root growth of fruit trees under water storage pit irrigation were studied:（1）The temporal and spatial distribution of soil moisture in orchard root zone under different irrigation treatments was studied,In space,the soil moisture under the water storage pit irrigation decreased gradually from the center of the water storage pit to the surrounding,while the soil moisture under the surface irrigation decreased gradually with the increase of soil depth.Under the coupling of time and space,the high value area of water content in storage pit irrigation changes alternately in the form of ellipse,while the surface irrigation changes in the form of saw tooth.The spatial and temporal distribution range of high water value area（24～30%）under water storage pit irrigation is wider.When the control level of soil water changed from W_50-80%to W_60-90%to W_70-100%,the high value area of soil water in spatial and temporal distribution gradually increased.A mathematical model of spatial distribution of soil moisture under different irrigation methods（surface irrigation and water storage pit irrigation）was established.The coefficient of determination R²was between0.7665 and 0.8998,and the simulation effect was good.（2）The temporal and spatial distribution of soil temperature in orchard root zone under different irrigation treatments was studied,Spatially,the soil temperature under water storage pit irrigation is gradually decreasing with the increase of soil depth,with the soil surface and water storage pit as the center,while the surface irrigation is gradually decreasing with the increase of soil depth.Under spatiotemporal coupling,the soil temperature under water storage pit irrigation and surface irrigation increased first and then decreased.The temporal and spatial distribution range of the median soil temperature（15～25℃）under water storage pit irrigation is wider.When the soil water control level changed from W_50-80%to W_60-90%to W_70-100%,the high value area of temperature in spatial and temporal distribution gradually decreased.A mathematical model of spatial distribution of soil temperature under different irrigation methods（surface irrigation and water storage pit irrigation）was established.The coefficient of determination R²was between 0.7124 and 0.7891,and the simulation effect was good.（3）The temporal and spatial distribution of soil oxygen in orchard root zone under different irrigation treatments was studied,In space,the change of soil oxygen saturation before and after irrigation was not obvious,but the change of soil absolute oxygen content was quite different.After irrigation,the absolute oxygen content of soil under water storage pit irrigation increased gradually from the center of water storage pit to the surrounding,while the surface irrigation increased gradually with the increase of soil depth.Under the spatiotemporal coupling,the high value area of soil absolute oxygen content under water storage pit irrigation changed alternately in the form of ellipse,while that under surface irrigation changed in the form of saw tooth.The spatial and temporal distribution range of high value area of soil absolute oxygen content（4～6%）under water storage pit irrigation was wider.When W_50-80%～W_60-90%～W_70-100%of water storage pit irrigation changed,the high value area of soil absolute oxygen content in spatial and temporal distribution gradually decreased.A mathematical model of soil oxygen spatial distribution under different irrigation methods（surface irrigation and water storage pit irrigation）was established.The determination coefficient R²was between 0.7123 and 0.7456,and the simulation effect was good.（4）The relationship between soil water and oxygen,soil water,temperature and oxygen under water storage pit irrigation(W_50-80%,W_60-90%,W_70-100%)was studied.The results showed that the soil water and oxygen were complementary distribution under the water storage pit irrigation.The temperature changes in the water oxygen is similar.The correlation between water and oxygen is good,and there is a significant negative correlation between water and oxygen.The correlation between temperature and oxygen is good,and the gray correlation is high.The relationship between water and temperature is closely related to oxygen,and the relationship between water heat and oxygen is high.The mathematical model of the relationship between water and oxygen is established.The coefficient R²is between 0.7765-0.8998.The mathematical model of the relationship between water heat and oxygen is established.The coefficient R²is between 0.7612 and 0.7904,and the simulation results are good.（5）The relationship between soil moisture,heat and gas and orchard photosynthesis under different irrigation treatments was studied.The results showed that the net photosynthetic rate was as follows:W_50-80%>W_70-100%>W_60-90%>CK.The net photosynthetic rate of fruit trees under water storage pit irrigation was better than that under surface irrigation.The relationship between soil temperature and net photosynthetic rate under water storage pit irrigation(W_50-80%,W_60-90%,W_70-100%)was analyzed.It was found that the net photosynthetic rate decreased exponentially with the increase of water content,increased gradually with the increase of soil temperature,and increased gradually with the increase of oxygen.There was a negative correlation between soil moisture and net photosynthetic rate,a positive correlation between soil temperature and net photosynthetic rate,and a positive correlation between soil oxygen and net photosynthetic rate.The mathematical models of soil moisture,temperature,oxygen and net photosynthetic rate were established,and the determination coefficients R²were 0.7124～0.8541,0.7654～0.8752 and 0.7504～0.8452,respectively.（6）The relationship between soil moisture,heat and gas and root growth under different irrigation treatments was studied.The results showed that the growth of fine roots was W_70-100%>W_60-90%>W_50-80%>CK.The fine root growth of fruit trees under water storage pit irrigation was better than that under surface irrigation.The relationship between soil moisture,heat and gas and root system under water storage pit irrigation(W_50-80%,W_60-90%,W_70-100%)was analyzed.The results showed that root system increased exponentially with the increase of soil moisture,decreased exponentially with the increase of soil temperature,and increased first and then decreased with the increase of soil absolute oxygen content.There was a positive correlation between soil moisture and root system,and a negative correlation between soil temperature and root system.The mathematical models of soil moisture,temperature,oxygen and root system were established,and the determination coefficients R²were 0.7856～0.9578,0.9003～0.9603 and 0.9504～0.9652,respectively.The coupling model of the relationship between soil water,heat and air coupling and root system is established.The simulation accuracy is high and the effect is good.