Suitability of agronomic water saving in karst areas and its enlightenment in the karst desertification control

The special "dual" hydrogeological structure in karst areas causes rainfall easily "leaking" into the ground, resulting a unique "karst drought". In these areas, drought and insufficient water resources seriously restrict the sustainable development of agriculture. In order to restore the ecology of karst desertification, develop ecological industries, improve the utilization efficiency of water resources, and advance water-saving agriculture in such areas, literature review method was applied to discuss the suitability of agronomic water-saving measures in karst areas. The results are as follows. (1) Agronomic water-saving measures including tillage, mulching, water-fertilizer coupling, chemical regulation, crop allocation and deficit irrigation can all enhance the crop WUE. For example, deep tillage and deep loosening increased the WUE by 15.1 % and 15.9 % respectively. The WUE of spring wheat under straw mulching increased by 17.17 %–43.01 % compared with that under mulching film. Increased density of intercropping corn and wheat saved 9.85 % of water. (2) The cultural or natural particularity of karst areas limits the application of all agronomic water-saving measures in karst areas, and therefore choices and adjustments are necessary according to local conditions: ① No tillage should be adopted because of the high output of labor force; ② straw mulching need to be crushed; ③ the coupling of water and fertilizer reaches better effect when applied to crops several hours before rainfall; ④ the shallow soil layer and the complexity of preparing water retaining agent make it unsuitable to use water retaining agent; ⑤ agroforestry with dwarf and dense planting is more suitable; ⑥ crop deficit irrigation can be carried out by using ecological small pools. Based on the above results, proposes are offered in the following. First, it is necessary to construct the optimal model of regional water and fertilizer coupling in karst areas, and apply composite agronomic water-saving measures. Second, it is suggested to establish a model of coordinating forest, grain and grass, and vigorously develop ecologically derivative agroforestry. Third, there is a necessity to strengthen the research and development of technology about soil and water leakage monitoring and resistance, and intensify studies on "five waters" transformation at the basin scale. The research results and implication are an important reference for developing water-saving agriculture, solving the short