| A scaling-up maize dynamic model applying to low temperature damage prediction in EN, China was established based on studies of predecessors on crop simulation models, spring maize growth and development and low temperature damage in EN. The purpose of this research is to meet to the requirements of maize low temperature damage predictions and to try to crop simulation model scaling-up applications.The low temperature damage of maize in EN is referred to inadequate thermal condition during growing season, which results in development stage postponed, growth influenced as well as immaturity. Therefore, a focus of this paper is to better simulate the maize development stages. An improved heat unit development model calculated as a function of daily maximum temperature and minimum temperature was established after some selected maize development models were compared with each other. Some crop parameters were derived and readjusted using 91 cases for observed development data and some field experiments data for spring maize in EN, China, and then, the model was validated by these data. The scaling-up regional parameters were mainly determined based on cultivar maturity types. The simulated results of development stages and of dry matter for various oranges were satisfied.As most of crop models were limited to validate for experiments data on plot or to simulate the mean response in a given regional area, the resolution to crop growth simulation model for scaling-up application was tried, using the spatial interpolation of daily weather data by geo-statistics principles combining scaling-up crop and soil parameters. The development and growth processes were simulated for 12 stations using daily weather data for 40 years (1961~2000). The index for low temperature damage was defined by the days of tasseling postponed. The years with low temperature damage and the related reduction of yield were analyzed using the index. Using scaling-up regional crop parameters and daily weather data in grids the development and growth processes in grids with 0.25' Q.25' were simulated for the year with typical low temperature damage and for mean climate condition in 40 years, respectively, and the spatial distribution on grids for simulated outputs in the study area was drawn by GIS tools.The model software system was developed by object orientated VB6.0 programming technology and based on module designed thought. There are potential and water-limited production levels in the model. The model with one day step includes development, growth, evapotranspiration, soil water balance et al. modules. The development process controls the growth process. An improved heat unit development module and an update evapotranspiration equation recommended by FAO in 1998 wereapplied to the model. A development stage index calculated module, a suitable sowing day calculated module, aimed at different requirements for simulation and application an alternative control module for more stations or for grids and or for single station was added. The main conclusions in this study are as follows:Using the index for low temperature damage defined by the days of tasseling postponed, the degree of low temperature damage was estimated. The results are very well and are conformed by historical cases. The model of development stage well simulates maize development stages and the response of development stages to low temperature damage.In most of the years occurring low temperature damage the yield decreased in planting medium-maturity cultivars areas, but the relations between the year with low temperature damage and the year with low yield was not dependent so well in planting late-maturity cultivars areas. One hand, in some degree the model can basically simulate responses of maize biomass to low temperature damage; on the other hand, it means that the parameters of late-maturity cultivar should be calibrated by more experiment measured data, and that the model will be modified further.Compared with ordinary statistical models, the method for... |
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