Experiments on irrigation efficiency using iodine-starch staining

The objectives of this study were to investigate infiltration patterns and irrigation efficiency under various soil texture and hydraulic conditions and to explore relationships between distributions of solute and flow modes under different irrigation conditions. An iodine-starch staining method was applied to visualize flow paths and solute transport, then totally 12 infiltration experiments under flood irrigation and micro-irrigation were conducted in the loam field and clay field respectively. Irrigation efficiency was evaluated using various indictors, including the application efficiency, deep percolation ratio, storage efficiency, and irrigation uniformity. Results showed that the redistribution of infiltration water was mainly attributed to the wetting patterns. Storage efficiency and irrigation uniformity increased with the increasing of irrigation amount, and the deep percolation ratio also increased significantly. Uniformity and deep percolation loss rate of solute distributions were less than that of the water distributions respectively. Redistributions of water and solute after infiltration provided more direct and comprehensive assessment for irrigation efficiency.