The Applicability Evaluation And Application On The Management Of Water And Fertilizer With DSSAT In The Hill And Gully Areas Of The Loess Plateau

The Decision Support System for Agrotechnology Transfer is a model which based onmodeling the growth of crop. It can simulate the daily growth of crop and respond manyfactors, such as the Genetic characteristics of crop, management measures, environment,the duress of water and nitrogen, pests, and so on. It was used to analysis the agriculturalexperiment, predict yield, and evaluate the risk of produce and the influence of climate. Italso can work on the simulation of productive capacity based on photosynthesis,temperature and rain, the optimal schedule for cultivation, and so on. The model also wasused to provide reasonable and effective policy decision and prediction. CERES(Crop-Environment Resource Synthesis System) is a model about corn which was foundby Ruthie who a professor of Michigan State University in1980s. It wasn’t only used tomodel the main process of crop growth, also to simulate the balance of soil nutrients(mineralization, nitration, denitrification, nitrogen fixation, leaching, absorbing andutilizing, and so on.) and water (effective rain, run off, evaporation, transpiration, and themove of soil water in plumb and level). It was one of the main crop models of DSSAT andwas used in China in the starting of21th.This study was based on the field experiment of spring maize in2002,2003and2005,at Ansai Farm Ecosystem National Field Research Station Shaanxi. The CERES-Maizewhich one of the main crop models of DSSAT4.5was used to simulate the growth period,yield and aboveground biomass of spring maize. To evaluate the applicability of the modelin spring maize planting, the simulated results were compared with the measured result. After the debugged of parameters, the CERES was used to model the growth situationamong the different treatments of spring maize under the conditions of2005. Thediscussion of the effect of water and fertilizer in the planting of spring maize was based onthe result of simulation. Some conclusions were received.1) The CERES-Maize model could do well in simulating the growth period,aboveground biomass and yield of spring maize at the Hill and Gully Area of the LoessPlateau with normal rainfall. The error on growth period was only3-days, both n-RMSEand MRE of simulated yield were less than10%, although there’s no good work onaboveground biomass, the result could be accepted.2) CERES could not reappear the situation of spring maize in field accurately in thecondition of less rainfall. It had a good job on growth period simulation except emergencedate which the error was9days. This model was also good at the yield simulating, with then-RMSE and MRE of simulated yield were6.47%and5.03%, respectively. The modelcould not be good at aboveground biomass modelling with little rainfall, with bothn-RMSE and MRE of simulated biomass were more than30%.There’s some work be done to study the process of the model, some consequenceswere displayed, the Kc of model which was evaluated with1, was different from the one inour research which was a value ranged from0to1. Because of over evaluating of Kc, theduress of drought was over estimated and the simulated values were less than the measuredone, during the process of growth of spring maize. In the other hand, the distribution ofrainfall which little at the beginning of the period and more and more in the later in2003was most different from the other two years. The rainfall in the later reduced the loss ofyield and above ground biomass because of the little rain in the start of period. During thegrain-filling period the increased dry material was assigned to seed first, others weremoved to stem, so the yield of spring maize could be simulated well, but there’s a big errorin simulating of above ground biomass. In order to do some good work in dry areas withthis model, it must be optimized deeply.3) Under the normal rainfall meteorological conditions (for example2005), the outputof model was that the result of growth simulation of spring maize with the treatment ofdifferent manure and nitrogen showed us it can reduce the loss of yield which because ofthe less nitrogen were used in the production of spring maize, by added more manure in the condition of rainfed. Both the two treatment which treatment M1N4with manure:7500kg/hm2and nitrogen:400kg/hm2, treatment M2N3with manure:15000kg/hm2andnitrogen:300kg/hm2could bring us the equal effect on yield and aboveground biomassincreasing, productivity of nitrogen. Both of them were the better treatments rather thanothers.4) With one irrigation during the process of spring maize growing, the result told usmaybe it have no useful to increase the yield that during the growth stage irrigated wateronce with both of manure and nitrogen were little used, this time the limitative factor ofyield may be fertilizer; on the other hand it had apparent effect on the yield increasing thatthere’s one irrigation during the growing stage under the more dosage of manure andnitrogen. In addition, the treatment Ig was the best one among the treatments in the equaldosage of fertilizer. This indicated that it is important to ensure the yield that assuredthere’s no duress during the growing stage of spring maize especially in the stage ofgrain-filling.