Study On Water-saving Mechanism And Calculating Methods Of Crop Water Requirement In Controlled Alternative Furrow Irrigation

Drought and water shortage are restricting seriously the sustainable development of social economy. China is a large country of irrigated agriculture, in which the shortage of water resources is very serious. Due to the underdevelopment of economy, traditional surface irrigation such as border and furrow irrigation is still taken as the dominant way in farmland irrigation, which leads to the great waste of water resources. Therefore, how to apply a new theory to study and improve surface irrigation technique in order to increase water use efficiency and water productivity in farmland, has become a key project in water-saving research of agriculture today.Furrow irrigation is a common way used in wide-row crops. But conventional furrow irrigation is difficult to meet the demands that crops are irrigated at proper time and with suitable amount of water. In recent years, according to the experimental results of controlled roots-divided alternative irrigation, controlled alternative furrow irrigation technique has been put forward through the deep investigation on the physical process of soil water moving into root zone, physiological process of roots absorbing water, dynamic properties and compensative role of roots, signal transmission and interaction between roots and canopy and so on. Controlled alternative furrow irrigation is proved to be an effective irrigation technique that has an advantage of saving water and not reducing yields in irrigating wide-row crops. At present, the studies about the controlled alternate furrow irrigation are focused on how it affects the water physiological indexes, water consumption and yields of crops. But, some problems such as the soil infiltrative parameters, irrigating water advancing, water redistribution in soil, calculation of crop water requirement and water consumption, and the upper and lower limit indexes of soil moisture, guiding a field irrigation after the controlled alternative furrow irrigation is implemented in field, have notbeen researched systematically and deeply. If these problems could not been solved commendably, the popularization of controlled alternate furrow irrigation will be affected. Therefore, an experimental study has been conducted on summer maize planted in field and lysimeters under a rain shelter for three years to solve the problems.This dissertation is divided into six chapters. In the first chapter, the improvement and development of furrow irrigation technique, theory foundation of controlled alternate furrow irrigation, and related research advance at home and abroad were analyzed and elucidated, and the main problems needing to be studied further and to be solved were put forward. In the second chapter, the soil infiltrative parameters, irrigating water advancing and water redistribution in soil were studied by adopting the controlled alternative furrow irrigation in field. In the third chapter, the ratio of soil evaporation to crop transpiration under different furrow irrigation ways adopted in summer maize field was analyzed by using the measured data in lysimeters. Next, the relationship between soil evaporation, surface soil moisture and leaf area indexes and the variation course of surface soil evaporation intensity in wet furrows after irrigation were studied. Finally, water requirement of summer maize and daily water requirement at each stage were determined based on the yield data under alternate furrow irrigation. In the fourth chapter, the effect of controlled alternative furrow irrigation on the ratio of root to shoot, filling rate, leaf physiological indexes, yield and water use efficiency of summer maize were discussed, and the lower limits of suitable irrigation for summer maize in controlled alternate furrow irrigation were analyzed and determined. The estimation methods of water requirement, and determination of basal crop coefficient and soil evaporation coefficient under the controlled alternative furrow irrigation in summer maize were studied and verified in the fifth chapter. In the last chapter, the m...