Improvement and Comparison of the Accumulated Temperature Model of Northeast Spring Maize

Spring maize in Northeast China plays a more and more important role in the national maize production. The gradually increase in acreage, the per unit area yield and total yield of spring maize have markedly improved since 1980s. Accumulated temperature is one of indexes which are commonly used in agricultural meteorological research and operation service. It's also used in crop model and regional thermal resource analysis which can reflect differences in demand of heat resources between different crops and varieties. And it can also be used to evaluate the suitability of heat conditions in a certain area for crop growth and development to avoid blindness of crops introduction. But in fact, the stability of accumulated temperature is relative, and it fluctuates with differences of crop varieties, locations, years and growth periods. It results in the limited application of the accumulated temperature index. Besides environmental conditions, the instability of accumulated temperature is also affected by different calculation methods. In general, accumulated temperature models are divided into two categories, including linear model and nonlinear model. 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.Based on observations of spring maize and meteorological data in Northeast China, the spring maize Sidan19 is taken as an example. The nonlinear accumulated temperature model proposed by Shen Guoquan with good stability is adopted to fit, and the influence of parameter selection on the stability of accumulated temperature is analyzed. The quadratic function of mean temperature to the liner model is revised and analyzed, and the nonlinear model is compared. Results show that the stability of accumulated temperature is related to the parameter P, more stable with smaller P. However, accumulated temperature calculated by the nonlinear model shows inter-annual and inter-regional differences. The main cause for the instability is different temperature strength and its less correlated with other meteorological factors. For each growth period, fitted curves between accumulated temperature and mean temperature are quadratic. The fitting effect of the accumulated temperature calculated by the revised linear model is better than that of Shen Guoquan nonlinear model. Moreover, the stability doesn't appear to be much different between two methods. Thus, the revision of linear model considering the mean temperature for spring maize in Northeast China is feasible, which can help revising agro-meteorological indexes and improving agriculture service capacity.