Study On Water And Salt Movement In Saline-Alkali Soil Under Alternate Partial Rootzone Irrigation

Soil salinization is a world problem. Experts predict that soil salinization problem will still exist, even worsen in the 21st century, and it will become one of the most important problems in the whole world. The salinized soil distributes vastly in our country; with the area approaching l.0×108ha. Soil salinization is mainly caused by water shortage. Therefore, soil salinization exists mainly in the regions lacking of water resources. At present, owing to water shortage and degradation of land resources, implementing water-saving irrigation, increasing soil throughput, improving and reusing salinized soil have played important parts in increasing agriculture production and making good use of water resources and land resources. The study of water and salt movement under different irrigation methods, will be of great importance in many aspects, including consummating salinized soil water-saving irrigation theories and mechanism, guiding traditional ground irrigation towards water-saving ground irrigation, ameliorating ecological environment, maintaining ecological balance, relieving water crisis and utilizing salinized soil with high efficiency.By combining laboratory tests with field tests under different irrigation methods and planting crop, these characteristics of coupled movement of soil water, salt and heat transfer and corresponding effects on crop growth were studied systematically. The main results are as follows:1. Under saturated and unsaturated soil in salinized soil, water amount of infiltration and flow velocity have obvious effect on desalinization. There are very prominent power function relationship between infiltration water amount and its desalinization ratio of unit water amount. In course of infiltration under different water presses, very prominent power function relationships between soil electrical conductivity of any soil depth and the infiltration time were founded.2. Test results of normal irrigation, alternate irrigation and fixed irrigation in plot of greenhouse show that salinity can't be expelled from soil or infiltrated into deeper soil layer because of limited water amount of water-saving irriation. The main functions of water-saving irrigation are: 1) to limit water infiltration into soil deeper layer with high salt content, then...