Experimental Research Of Fruit Tree Root Water Uptake Model On The Condition Of Water Storage Pit Irrigation

Water storage pit irrigation is a new method, suiting irrigation of hilly area, combining of solving drought problem and controlling water and soil losses. The maximum character of the method is that water directly infiltrates into the rhizosphere soil zone, so the water distribution is in the middle-depth soil of rhizosphere. Meanwhile, because the surface of the storage pit walls is a near-air surface, the air permeability of the middle-depth soil was improved. It is therefore beneficial to roots breathing and plunging deeper into the soil. Deeper roots not only can absorb nutrient and water from bigger area but also improve drought resistance of fruit trees. The purpose of increase production also will be achieved. To study on water content movement in fruit tree rhizosphere zone, root distribution and root water uptake on condition of water storage pit irrigation has a great significance for the popularization and application of this method and improvement water use efficiency in the arid and semi-arid areas.Combine the Shanxi Province Science and Technology key problem projects (No.051115 and No.2007031069), the technical line of numerical simulation and experiment was adopted for Red Fuji apple root water uptake research. First, the spatial characteristics of rhizosphere soil moisture distribution and root distribution were investigated in the Red Fuji apple trees orchard. Then the water uptake model of fruit tree water-uptake root was established on the basis of rhizosphere soil water dynamics principle and validated by farm field data. The main contents as follows:1. The study of soil moisture content varying in fruit tree rhizosphere. The analysis result of soil moisture content routine measurement data by the soil auger was analyzed as follows: The range of variation of soil moisture content on filed surface was biggish. The influence of soil moisture by natural environment and human factors gradually decreased along with the depth increase. The soil moisture content obviously reduced in 90～110cm soil zone, because of storage pit. It was therefore improved on air permeability of the middle-depth soil, beneficial to roots breathing and rapid changes in root water uptake rate. So the soil moisture changed largely.2. The study of spatial characteristics of fruit tree water uptake root. We got the following conclusions to the analysis result of fruit tree root routine measurement data by the WINRHIZO, which was used for analysis root. The fruit tree roots distribute between 0 and 120cm. The root length density, which is exponential relation with depth, reduces along with the increased depth. The root distribution was analyzed before and after water storage pit irrigation. The peak value of water-uptake root length density moves down after water storage pit irrigation, but the movement is not very great, because of the method implemented for less than a year.3. The study of fruit tree water uptake model. The two-dimension root water uptake model was established by different method of the root density data and soil moisture dynamic data. The improved Molz-Remson form established by the root density data, cited root water uptake effect function, on which soil water potential impacted. The simulating result showed that this model could correctly reflect the root water conditions of fruit trees. The other model was established by the soil moisture dynamic data. Although this way need the computer program to conclude root water uptake intensity, and need more mathematic conclusion, but it can avoid the hard works of roots density measuring, and would hurt less fruit tree roots. The fruit tree root water uptake models established through this ways has higher simulation accuracy.4. The simulation study of soil moisture movement in fruit tree rhizosphere. The soil moisture movement model containing root water uptake was established in fruit tree rhizosphere. The model was solved by the ADI method and validated by field data. The results show that calculative results were in good agreement with the experimental results, and there is better consistency. We can see that the established mathematical model could correctly reflect the soil moisture movement on the condition of water storage pit irrigation. The root water uptake function could correctly reflect the actual situation, so the numerical solution is feasible. But this way to establish root water uptake model according to the root density data is compared with another which according to the soil moisture dynamic data, the latter higher than former in accuracy.The research will provide the basis for saving water and fighting a drought mechanism of water storage pit irrigation in this paper. The results have important value for further research and popularization of water storage pit irrigation.