The comparison of temperature elements measured in station and in paddy filed

Background and objective: Temperature is one of the most basic meteorological parameters of frequency applications in agricultural science and technology. The aim of this study was to compare the data recorded in a standard synoptic weather station (Rasht agro meteorology station) and temperature recorded in rice fields and in the average canopy height of rice.
Material and methods: For this purpose, the temperature of paddy field installed in standard screen box is measured in 65 cm in height using thermograph and thermometer, and it was compared with the data of the Agricultural Meteorological Station in the vicinity of the farm.
Results: Results show that temperature changes during the season at the station and farm and in all measurements are incremental, but the increase in the maximum is higher than the minimum. The mean comparisons of the canopy have a significant difference in measurements of farm and the station. Differences in maximum temperature are greater than the minimum temperatures, indicating that the effect of farm microclimate on reducing the maximum temperature is more effective. The differences of field (daily) thermometer and stations in the whole season were between 1.1 and 6.1 degrees Celsius respectively in average temperature and maximum, but no significant difference in minimum is seen. In this study, growing degree days (GDD) calculated from three sources has significant differences and reflects the importance of accuracy in the calculation of these parameters in agricultural meteorology. Before the end of the growth phase (Phase II) there is no significant difference between the thermometer in field and station, so station data can be used directly instead of field data. Most differences are seen in the middle stage and end-stage growth (0.9 and 2.3 degrees Celsius on average and 1.4 and 2.9 degrees Celsius of the maximum). Maximum and mean temperatures of the whole period at stations with coefficients of determination values, 0.79 and 0.74, can be converted to farm temperature. By stopping irrigation and entering to complete maturity, the similarity between the field and the station records become greater. Because minimum temperatures last longer than the maximum and there is sufficient time for thermometer to be adjusted to the environment, the registered minimum in the thermograph has less difference than the maximum data in comparison of the same elements in stations.
Conclusion: Development of canopy causes significant differences between data recorded in paddy field and station and difference in maximum temperature is more than minimum temperature. The accuracy of data which is measured by thermograph and to extract maximum and minimum temperatures, it is important to consider the persistence of the temperature, If the temperature continues longer hours it has probably more accurate results. However both maximum and minimum temperatures have increasing trend, the difference between maximum and minimum increase during the season in all methods. Rain reduces the difference between the maximum and minimum temperature. With the interruption of irrigation and reaching maturity stage, the difference between the station and the farm is not meaningful.