Abstract
Using the Arrhenius equation, periods of varying temperatures can be converted to days of standard temperature. The number of days transformed to standard temperature (DTS) is useful for predicting plant growth under different temperature conditions. Because calculating precise DTS using temperature data including diurnal variation is laborious, many studies have used only daily mean temperature. In this study, I examined the extent to which DTS is misestimated by calculation using only daily mean temperature, and tried to correct the estimation method. First, a formula to calculate DTS for semidiurnal constant temperature was derived and adapted to the number of days until seedling emergences of rice plants under semidiurnal constant temperature; days until emergence could be calculated following this formula. Next, based on air and soil temperatures over 3 years, the extent of misestimation of DTS was estimated and it was found to be less than 1% for soil temperature but close to 6% for air temperature. This suggests the importance of the diurnal variation of temperature for DTS calculation. Because there was a close relationship between the extent of underestimation and the daily range of temperature, the DTS formula was improved considering the daily temperature range. By this correction, misestimation was reduced to less than 0.3%, even for air temperature, showing that precise DTS can be easily calculated using daily mean temperature and daily temperature range.
