Study On The Energy Of SPAC System And Root Uptake Model In Saline Soil

Under the background of decreasing the water diverted from the Yellow River, giving consideration to the agriculture production and making the soil salinization under control, aiming to the complex mechanics of water-salt stress, this paper mainly studied crop root uptake model and energy state of different interfaces of Soil-Plant-Atmosphere Continuum in saline soil of north china. The researching object is the oil sunflower that is the main economic crop. The study revealed the water translocation mechanics of SPAC system, and established crop root uptake model in saline soil. It offers the croeoretical basis and technical support for agriculture productivity and water-saving irrigation, and enriches and consummates the theory of water-saving irrigation in saline soil. Main conclusions as follows: (1) Influencing factors of leaf water potential includes soil water content, soil salt, net radiation, atmosphere humidity and atmosphere temperature. Through the sensitivity analysis about influencing factors, we can discovery the soil water content is the most significance influencing factor, atmosphere temperature is more significance and the other influencing factors are significance. Through water shortage diagnosis, showing leaf water potential should great than –2.5 Mpa in light saline soil, and great than –3.0 Mpa in medium saline soil in growing season. On the basis of analyzing the influencing factors, the BP Neural Network movement model of the leaf water potential in saline soil was established. Through training, the topology structure chosen is 7:24:1, and the average absolute relative error is 13.8%. (2) The influence caused irrigation (rainfall) is to each layer soil matric potential reduces with depth of increment. After irrigation, with varying of the temporal hour soil matric potential follows periodic increase and decrease regularity, Its charging periodic time is 24-hours. When the change of soil content was not obvious, soil temperature is the main influencing factor. (3) Soil matric potential, leaf water potential and atmosphere water potential is diversity in temporal and spatial variation, the daily vary of soil matric potential is not large, while leaf water potential and atmosphere water potential is large. Atmosphere water potential is lees than leaf water potential and soil matric potential, the difference between them is about 1～ 2 order of magnitude, and leaf water potential is less than soil matric potential. (4) This paper studied the ecological and physiological features, the temporal and spatial variation regular of sunflower root. With crop growing period traction, the root system increases, maximizes at florescence, and reduces at maturity. With the depth increase, the root system reduces. Branch root locates superficial coat (0~10cm). The growth of root was restricted by soil salt severely, and it is very obvious at seeding stage and maturity. (5) The soil-water movement parameters are measured in laboratory and field, at the sometime, the soil matric potential measured in the field is scaled and established the mathematic model between the soil matric potential and the saturation degree. The root uptake water rate is calculated based on the data of soil matric potential and soil water content. With crop root development, the root uptake water rate increases, and maximizes at florescence. The main uptake water layer locates the depth from 0 to 50cm, and the maximal uptake rate move between 20 and 40cm. It was restricted by soil salt severely. The formula of ET=E+T was used to check the accuracy of the root uptake water rate. And established the root uptake water model based on BP Neural Network in saline soil. This study offers the theoretical basis for researching the soil water movement, and it is the basis of researching the SPAC system in saline soil.