Process-based Simulation Model For The Critical Nitrogen Demand Of Drip Irrigation Spring Wheat

【Objective】This study aimed to develop the simulation model of drip irrigation spring wheat based onphysiological development time. and on this basis,it explored to develop the critical nitrogen concentrationdilution curve model and the critical nitrogen demand quantitative model based on process of drip irrigationspring wheat, and provided theoretical basis for the optimal management of nitrogen in the drip irrigationspring wheat production.【Methods】The experiments of sowing date and cultivar were carried out in field to record each stage ofgrowth and development of drip irrigation spring wheat with the principle, that the physiogenesis time ofcrop was always constant, and develop the simulation model of drip irrigation spring wheat. On this basis,the effects of different amounts of nitrogen on dry matter, nitrogen accumulation and output of dripirrigation spring wheat were analyzed by means of setting field experiments with different amounts ofnitrogen. The critical nitrogen concentration dilution curve simulation model was developed based onphysiological development time.And it was combined with the dry matter accumulation model of dripspring irrigation wheat growth to develop the critical nitrogen demand quantitative model of drip irrigationspring wheat based on process.【Results】The drip irrigation spring wheat growth periods could be well simulated by the model based onphysiological development time. The physiological development times of the drip irrigation spring wheat infour stages （from sowing to seedling, from seedling to jointing stage, from jointing stage to heading, fromheading to mature） were differently6.2,16.3,13.3,27.6d. And the physiological development timerequired in the whole stages was63.4d. The model had good stability between years.It was proved from analyzing the effects of different amounts of nitrogen on dry matter, nitrogenaccumulation and output of drip irrigation spring wheat that different nitrogen application would not affectthe dry matter aboveground of drip irrigation spring wheat and the dynamic change law with physiologicaldevelopment time of nitrogen accumulation amount. But it had a greater influence on the characteristicparameters of every model. Characteristic parameters of the models in the situation of the appropriatenitrogen application were the most harmonious with the highest maximum growth rate. On the other hand,fast growing period starting time of nitrogen accumulation of the aboveground plant was earlier than drymatter with7days or so in physical development. It showed that nitrogen accumulation was the premisecondition of dry matter accumulation.Compared with other treatments, the nitrogen quantity of the N2treatment(300kg·hm^-2) was optimum, and the aboveground plant of the drip irrigation spring of the N2treatment wheat could achieve the maximum amount of dry matter and nitrogen accumulation meanwhilewith the highest yield.With the increase of the dry matter of above-ground plant parts of drip irrigation spring wheat,nitrogen concentration tended to reduce. And they conformed to power function relationship. Studiesshowed that critical nitrogen concentration dilution curve simulation model of above-ground plant parts drip spring wheat was NC=5.03W_max^-0.38, which was verified and showed that had good stability betweenyears. At the same time, through combining with the dry matter accumulation model to develop thecritical nitrogen demand quantitative model of drip irrigation spring wheat, and by using of nitrogennutrition index and critical nitrogen demand dynamic change, people could make accurate decisions aboutthe applying nitrogen content of drip irrigation spring wheat.【Conclusion】The threshold nitrogen demand quantitative simulation model, which was established basedon physiological development time and the critical nitrogen concentrations dilution curve simulation model,could provide theoretical basis for precision fertilization of drip irrigation spring wheat.