Study On Root Water Uptake Model Of Apple Tree

To master the condition of plant root water uptake accurately, to understand the trends of soil water, are not only benefit to draw up the irrigation schedule resonably, to guarantee agricultural water saving, to ensure high and stable yield, but also are indispensible links of the SPAC model which is study on the water transfer in soil-plant-atomosphere continuum, and of the SVAT model which is study on the regional water transfer in soil-vegetation-atomosphere system. Since 1950's, many researchers in several fields have studied on the principles and characteristics of plant root water uptake, and on the root water uptake models. These studies have important applied value to agriculture irrigation, water resource, and other fields.To review the existing root water uptake models, the studies are mainly focused on crops: there are few studies on trees, desert plants, and agri-forestry system. However trees are important parts of the vegetation on the earth. The impacts of the trees transpiration on the water transfering relationship of the soil-vegetation-atomosphere system can not be neglected. In recent years, the orchard areas in northern China becomes bigger and bigger. The apple tree orchard is a considerable part of the orchards. The quantity of orchard water using is quite large. So scientific management of orchard water using is quite important. We attempt to study on the apple tree root water uptake model in orchard. Through the study works, we can not only provide scientific thoery to orchard irrigation management and water optimal controlling, but also provide valuable reference to other trees root water uptake models.Through field experiments and thoeretical analysis, we have got the following conclusions to the apple tree root water uptake models:(1) The apple tree roots distribute widdly and deeply. Its row interval and colum interval are bigger. The ununiformity of apple tree roots spatial distribution is notable. So whether establishing apple tree root water uptake model according to root density data, or establishing apple tree root water uptake model according to soil moisture data, the measuring points of root density and soil moisture are more. So the measuring points should be arranged appropriately. Whether the one-dimensional roots length density distribution of apple tree, or the two-dimensional roots length density distribution of apple tree, all of them can be fitted by exponent function. Theone-dimensional roots density distribution of apple tree fitted by exponent function is as following:I(z) = 0.80071, e-39022'" (1)The two-dimensional roots density distribution of apple tree fitted by exponent function is as following:) (2)(2) The apple tree root water uptake intensity is mainly determined by effective roots length density and soil water potential. Under the condition of full soil water suppl), the root water uptake intensity is in positive proportional to effective root length density. The one-dimensional root water uptake intensity distribution function of the measured apple tree under full soil water supply is as following: 3 ) The ways to establish root water uptake model according to the data of roots density is the most preferable ways at present. This ways conform to the habits of most people. It doesn't need the computer program to conclude root water uptake intensity. And doesn't need more mathematical conclusion. So this ways is adopted by many people. But the measuring works of apple tree roots density is hard. And the roots measuring would hurt more apple tree roots. Although the ways to establish apple tree root water uptake models according to the data of soil moisture need computer program to conclude root water uptake intensity, need more mathematical conclusion, and need to wet root zone soil uniformly; but this ways can avoid the hard works of roots density measuring, it would hurt less apple tree roots, and the apple tree root water uptake models established through this ways na...