Experimental Study On Crop Water Stress Detecting & Irrigation Index

Water scarcity has become a major factor that constraints the development of agriculture, consequently it is impendent to carry out water-saving agriculture. Study on crop's water stress diagnosis index and irrigation control index in an attempt to ensure timely and proper irrigation is one of the essential approaches to reduce the waste of water resources, develop sustainable agriculture and rationally manage water resources.Field trials were conducted at Daxing Irrigation Experimental Station of China Institute of Water Resources & Hydropower Research (IWHR). Overseas advanced equipments were used to automatically monitor crop's physiological index, such as changes of stem diameter, sap flow, and leaf surface temperature. The observed data of crop's canopy temperature, soil moisture, photosynthetic rate, transpiration rate and stomata conductance in combination with the above monitoring data were used to analyze the capacity and sensitivity of various index's responses to water stress; to establish the relationship between soil moisture and physiological index and water deficit level of various crops; and to determine the irrigation control index and their scale value of some major crops according to the methods of monitoring and collecting soil moisture information, as well as the sensitivity and stability of water deficit diagnosis index. Following suggestions and conclusions have been come up with from the experimental results:(l)Various water supply conditions have significant impact on the growth of winter wheat, spring maize and summer Soya bean. Crop's height and leaf area index increase with irrigation frequency. Compared with one irrigation, plant height and unit head grains of winter wheat with three irrigation increase by 8～10cm and 3～5 respectively; the dry biomass of spring maize with two irrigation increases by 20～80g/m ; compared with no irrigation, the plant height and the dry biomass of summer Soya bean with three irrigation increase by 2～ 10cm and 20～60g/m~2 respectively. That the maximal irrigation quantity does not result in the maximal yield shows appropriate limiting irrigation can increase yield and improve the water use efficiency.(2) The key water requirement period for winter wheat are jointing stage and booting-flowering stage, for spring maize are jointing stage and elongation stage to the filling sage, and for summer Soya bean is flowering-poding stage. Adequate Water Supply in these stages is very important to increase yield. Appropriate deficient irrigation at seedling stage...