Relations between evaluation of soil temperature beneath film mulch and number of measurement points for soil temperature.

摘要

The objective of this study is to elucidate how the number of points for measuring soil temperature affects the evaluation of soil temperature between two experimental plots. Distributions were made based on a frequency table describing the differences in soil temperature. Evaluation of soil temperature based on the number of measuring points was discussed from the stand point of the range (maximum-minimum), maximum (class's upper limit), minimum (class's lower limit), and largest frequency class of the distributions. Regarding on the range of distributions, clear differences based on the number of measuring points were revealed between two plots without plants, but their seasonal variations were not clarified. Between the two plots containing plants, the seasonal variations were very marked. The mean maximum and minimum values of the distributions shown on the frequency table of soil temperature during the experimental period approached a fixed value by increasing the number of measuring points. However, differing tendencies were observed according to the presence of mulching and plant cover at the plot. The largest frequency class was affected by mulching and plant cover. Variations in air temperature were the same as variation in the soil temperature, and the mean values of changes in air temperature during the experimental period were larger than those of the soil temperature.