Comparison Of Two Growth Models For Cotton Under Drought And Waterlogging Stresses

Drought and waterlogging are major stresses in the process of crop growth,which affect crop growth and important metabolic processes(e.g.root respiration,water and nutrient uptake),and affect the final production.Crop growth model is a comprehensive simulation of various growth processes of crop,which is an important approach to evaluate disaster prevention and mitigation under drought and waterlogging.The dissertation aims to provide an in-depth study on two cotton growth models under drought and waterlogging and the main research works is as following:In the first chapter,background and significance of study is provided.A detailed review of crop growth models,the effect of water stress on cotton and sensitivity analysis of model,and the main research work is summarized.In the second chapter,OZCOT model and CROPGRO model are introduced systematically,which includes photosynthesis,respiration,assimilation,leaf area index,budling growth,the distribution of dry mass,and water stress.The data required for the operation of the two models are introduced.In the third chapter,the experiments are introduced under drought and waterlogging,which are included in the establishment of model database,the general situation,observation facilities,experiments treatments and soil in Wuhan University Irrigation and Drainage Experiment Station(WUIDES).The database of two models imput are also introduced and compared.In the fourth chapter,based on the data of WUIDES,the parameters of APSIM-OZCOT and DSSAT-CROPGRO-Cotton model are calibrated and verified,the outputs of model are growth period,total dry mass,seed cotton yield,leaf area index,soil water content,followed by analyzing the difference of models and the applicability and limitations of models,which shows that:? The CROPGRO model based on the physiological development day(PDT)is better than the OZCOT model based on the effective accumulated degree(GDD).? In CROPGRO,the RMSE of total dry mass was beween 1107-3664kg/ha,in OZCOT,the RMSE of total dry mass was beween 1232?2376kg/ha,the CROPGRO model has better predictions of yield under waterlogging.? In CROPGRO,the RMSE of seed cotton yield was beween 699-1544kg/ha,in OZCOT,the RMSE of total dry mass was beween 633?1496kg/ha.The buds fall off quickly which is difficult to simulate under water stress,and the results of simulation are not satisfactory.It is necessary to reveal the mechanism and to develop simulation method of cotton growth responding to water stress in the future.? The relative mean leaf area index of OZCOT ranges from 0.865 to 0.984 and CROPGRO ranges from 0.820 to 0.905.the mechanism and simulation method of CROPGRO is satisfactory under water stress.? The simulation values of soil moisture content during growth period could reflect the change trend of the actual values,and the RMSE of CROPGRO was between 0.057 and 0.062 cm3·cm-3,OZCOT was between 0.032 and 0.056 cm3 · cm-3.The results of dynamic simulation of soil water under water stress showed that the great simulated error of soil moisture in different degree of water stress.The model evaluation indexs were in credible range which showed that the parameters were matched reasonably,therefore,the corrected models had certain applicability.In the fifth chapter,the Morris method and extended Fourier amplitude sensitivity test(eFAST)method were applied to analyze the sensitivity of the APSIM-OZCOT model and DSSAT-CROPGRO-Cotton model under water stress,which shows that:The most sensitive parameters for OZCOT model were successively:governs pot rate of squaring in thermal time(Sqcon),the assimilate reduction factor for waterlogging(wlog_carcap_red),soil moisture content,parameters associated with its own leaf area growth(Flai,RLAI),effective accumulated degree(DDISQ).The most sensitive parameters for CROPGRO model were successively:Time between plant emergence and flower appearance(EMFL),Time beween first flower and first seed(FLSD),Time beween first flower and physiological maturity(SDPM),Specific leaf area of cultivar under standard growth conditiions(SLAVR),Light intercent coefficient(KCAN).With the deepending of waterlogging stress,the sensitivity of KCAN increased,along with SLAVR,Maximum fraction of daily growth that is partitiioned to seed+shell(XFRT)decreased.It is showed that by comparison of the results of the two sensitivity analysis methods:the overall trend is the same and the sensitivity of the key parameters is reflected,the amount of the key parameters of eFAST are more than that of Morris,which need small samples;and that the eFAST method,the results of OZCOT model which agree well with those derived from the method of Morris.So Morris is convenient to use.In the final chapter,the works of the whole paper are summarized,and suggestions for future research works of crop models of cotton under water stress research are given.The study of APSIM-OZCOT has not yet conducted in our country,and it is rare to analyze the CROPGRO and OZCOT.In aspects of sensitivity analysis,less research appeared under waterlogging stress,which affect the accuracy of the growth process.So we choice the obove-mentioned content as the topics of this thesis.