Summary:

This paper presents the results of a comparison of the average daily air temperature calculated based on different measurement procedures. Data for the research came from measurements of automatic weather station located at the Research Center of the Faculty of Agriculture and Biotechnology, University of Technology and Life Sciences at approximately 20 km from Bydgoszcz. Series in-cluded data from of the period 2000-2012 with the exception of 2005, 2006 and 2010, due to incomplete series caused by technical service of measuring sensors. Automatic weather station has been programmed for 5-minute sampling intervals, and then the data were stored in the logger memory, as the average of an hour. Hourly air temperature values and the values of maximum and minimum temperatures were used to calculate the average daily air temperature with selected methods. The aim of this study is the evaluation of selected methods for computing average daily temperature in relation to the method that according to the WMO best estimates the daily average (calculated from 24 observation term). Furthermore indirectly determine whether a change in the method may affect the assessment of the current water needs of plants. The research found that the average daily air temperature values calculated on the basis of various mathematical formulas differ from the value of the 24- hour average. The use of hourly data from automated stations to estimate the rates of water consumption should be preceded by an analysis that indicates how these differences may affect the determination of terms of irrigation.