Modeling of phenological development in winter wheat to estimate the timing of heading and maturity based on daily mean air temperature and photoperiod

Prediction of phenological development of wheat (Triticum aestivum L.) is important for proper agronomic management and schedule planning. A model to calculate developmental rate (DVR) for short-day plant was applied for long-day plant to estimate the timing of heading and maturity of winter wheat using the concept of DVR. The DVR from emergence to heading was expressed using a function of daily mean air temperature and photoperiod. The DVR from heading to maturity was expressed using a function of daily mean air temperature only. The model was examined based on a field experiment in Kumamoto, Japan, in the 2003 and 2004 growing seasons. Three cultivars of winter wheat (Chikugoizumi, Saikai-185 and Iwainodaichi) were used to examine how the parameter values differ with cultivar. Calculated values for duration from emergence to heading and from heading to maturity showed good agreement with observed data over a wide range from 35-170 days and 30-55 days, respectively. Root mean square errors of the model estimation were 4.2-4.9 days for heading date and 1.7-2.8 days for maturity date, respectively. Phenological differences among the cultivars were mainly reflected in parameters expressing the DVR response to temperature. From emergence to heading, the temperature when the DVR is half of the maximum rate (Tsub(hv)) differed with cultivar from 3 to 9degC. The Tsub(hv) value was higher for a cultivar with a low degree of winter habit (Chikugoizumi), and lower for cultivars with a high degree of winter habit (Saikai-185 and Iwainodaichi), From heading to maturity, a parameter (Am) that expressed the DVR slope with change in temperature showed a higher value for Chikugoizumi, and lower values for Saikai-185 and Iwainodaichi. The model will be useful for predicting the phenological development of winter wheat and understanding the phenological response to climate change.