Study On Improvement Of Crop Simulation Model WheatSM

According to the physiological and ecological characteristics of winter wheat, based on the former wheat simulation model (WheatSM and WHTMOD), four new modules to simulate stem and tillering dynamics, yield formation, soil water balance and nitrogen balance in soil-crop system, respectively were added. The keystone of this paper was to establish and calibrate and validate these four new modules.WS&TSM simulated wheat tillering increasing and decreasing dynamics in four growth periods, from seeding to over-winter, from over-winter to green-returning, from green-returning to jointing and from jointing to heading, respectively. The effects of cultivars, temperature, assimilate supply on shoots, water and nitrogen factors on tillering process were integrated into this module. And it discussed cold acclimation before winter and death rate during winter. WYSM considered not only the effects of low temperature, water stress from panicle to grain filling stage and high temperature at late growing season on the formation of wheat grain numbers, but also the effects of temperature, water stress and N/C ratio of grains on actual grain weight, the source and sink relation was also integrated to modify potential grain-filling rate. Finally the method of yield components based final yield of winter wheat was developed. WTSM considered different processes of water in SPAS system. WNSM was focus on soil supply nitrogen, crop demand nitrogen and nitrogen distribution and translocation in various organs of winter wheat.The calibration and validation of these four modules has been conducted by experiment data in Beijing and Henan province. The results show that (1) WS&TSM simulated values are very close to the measured values, linear correlation coefficient (r) is 0.96. At the same time, it can reflect water stress effect on tillering dynamics and difference during winter in different regions. (2) WYSM prediction capability is pretty good. Grain numbers, grain weight, yield and grain filling process were predicted with an NRMSE of 4.2%-10.9%, and the adjust linear coefficient of determination obtains 0.88-0.99. (3) WTSM can reflect soil water dynamics during whole a growth season and difference among different water treatments well. (4) WNSM can reflect changing trend of distribution and translocation of nitrogen in different organs in whole a growth season.These four modules have not only good mechanism in model building, but good simulation capability and applicability. The new model can be used to predict canopy structure changing, to prevent disasters such as cold resistance, frost damage and dry hot wind and so on. Therefore, Compared to parallel studies both home and abroad, this study has made progress, therefore, it is of both theoretical and practical significance.