Simulation Based Optimization Model For Irrigation Scheduling Of Winter Wheat And Summer Maize Rotation Farmland And Its Application

In North China, winter wheat and summer maize rotation is the maincropping pattern. For the winter wheat-summer corn rotation system,optimization of irrigation scheduling on annual basis is of great significance tothe increase of water use efficiency. The research focus on a simulation basedoptimization model optimal irrigation scheduling for crop rotation system and itsapplication.The meteorological data and irrigation experiment data of YongledianIrrigation Experiment Station in Beijing were used. By analysis themeteorological data in the study area, the variation trends and correlation ofprecipitation and reference evapotranspiration series were analyzed. A jointdistribution model of them was built to determine different hydrological years.For simulation models, a soil water balance model was used to simulate thevariation of field soil moisture and crop evapotranspiration process, and waterproduction functions of winter wheat and summer maize were used to estimatecrop yield. Simulation based optimization model for irrigation scheduling of asingle crop and multi-objective simulation based optimization model for winterwheat and summer maize rotation system were proposed. The Geneticalgorithm(GA) and non-dominated sorting genetic algorithm (NSGA-Ⅱ) wereused to solve these optimization models, respectively.The irrigation scheduling optimization results show that the key irrigationperiods are heading to filling stages for winter wheat, and shooting to fillingstages for summer corn. The total crop yield increases with the irrigation quota,while the marginal benefit of irrigation decreases. The crop evapotranspirationalso increases with the irrigation quota, while the amount of soil water utilizationdecreases with the irrigation quota.According to different goals and constraints, the solution of the multi-objective optimization model could be divided into two categories. One took thecrop yields of winter wheat and summer maize as two objectives, and a dynamicpenalty function was introduced for the constraint of irrigation quota. The othertook the total production of two crops and total irrigation water used as two objectives. Irriagtion date and quota of each application were taken as thedecision variations. Results show that the total production and the production ofwinter wheat and summer maize are nearly the same for both categories, so as tothe range of optimal scheduling time. Compared with the first type model, thesecond type model couldn’t balance the interests of the two crops in the case ofwater shortage, and resulted in uneven allocation of irrigation water betweenwheat and maize due to different price of two crops. Therefore, the first typemodel is recommend for irrigation scheduling in the study region.The multi-objective simulation based optimization model for irrigationscheduling of winter wheat and summer maize considered the time sequence ofrotation farmland, and could balance the allocation of irrigation wate r betweencrops. This can determine the key irrigation dates and quota of each application.These results can be used to guide irrigation practice in the study and similarregions.