Impact Factors Of Accumulated Temperature Stability And Improvement Of Accumulated Temperature Model Of Northeast Spring Maize

Accumulated temperature is one of the indexes which are commonly used in agricultural meteorological research and operation service.But in fact,the accumulated temperature is unstable fluctuating with the differences of years,locations,and crop varieties.Therefore,how to choose and revise the existing model for stabilizing the calculation value of accumulated temperature and making it fit well with the actual situation is of great significance for agricultural production and meteorological service.Moreover,there are numerous maize varieties and it is important to establish the general accumulated temperature model considering varietal attribute and more extensively applicable scope to improve the application ability of the model.Based on the observations on the growth and development of spring maize and meteorological observation data in northeast China,the spring maize “Sidan19” is firstly taken as an example in this study.The nonlinear accumulated temperature model proposed by Shen Guoquan(or simplely NLM)with good stability is adopted to fit,and the influence of the selection of parameters on the stability of accumulated temperature is analyzed.The quadratic function of the mean temperature to the liner model(or simplely LM)is revised(which is called TRM after revision)and analyzed,and the nonlinear model is compared.In order to analyze the applicability of different northeast spring maize varieties in the application of NLM,three other varieties with more observable years and stations are selected,“Dongnong 248”,“Longdan 13” and “Danyu 13”.NLM with good stability is adopted to fit.Biological significance of parameters and the relationship between parameters and varieties or mature period are analyzed.The NLM has been improved effectively.In addition,two varieties are selected for verification.The results show that: the stability of accumulated temperature is related to the parameter P,more stable with the smaller P.Accumulated temperature calculated by the nonlinear model of Shen Guoquan exist inter-annual and inter-regional differences.The main reason for the instability is different temperature strength and its less correlated with other meteorological factors.For each growth period,the fitted curves between accumulated temperature and mean temperature are quadratic.The fitting effect of the accumulated temper ature calculated by the revised linear model is better than that of Shen Guoquan nonlinear model.Therefore the revision of linear model considering the mean temperature for spring maize in northeast China is feasible.There are no invalid parameters in the fitting equations of the four maize varieties.The parameter P is determined as 0.5 based on the smallest variation coefficient of accumulated temperature.There is a significant correlation between parameter K and parameter Q,indicating that the parameter K may be only a statistical parameter with no clear biological significance.There is a significant difference of accumulated temperature among varieties.The relationship between the parameter Q and the mean value of effective accumulated temperature or active accumulated temperature during the whole growth period is found to be of good correlation,which indicates that Q is related to the mature period types of different maize varieties because different accumulated temperature means different mature period types.Therefore,a general model applicable to different varieties is proposed whose parameter Q and K are represented by effective accumulated temperature or active accumulated temperature.Our findings get good application results and have importa nt implications for revising agro-meteorological indexes and improving agriculture service capacity.