寒地水田の蒸発散に関する研究 (1)

抄録

This paper deals with the results of measurement of evapotranspiration from the paddy fieild at Kuroishi City situated in the cooler region of Japan, from 1953 to 1956.
The amounts of transpiration were below 1mm/day in the early growth stage of rice plants and increased gradually with their growth (Fig. 1). But, the amount of evaporation decreased with their growth (Fig. 6).
The evapo-transpiration rates to the evaporation E obtained from the meteorological observation field lay within about 1.0-1.3 in the early growth stage and increased after the young ear formation stage. But the rates decreased again from about the tenth day after heading (Fig. 7).
Two peaks of the transpiration rates to E were found after the young ear formation stage and the heading stage. From the index of growth amount ln (l and n mean respectively the plant length and the number of stems per unit area), the transpiration rate t/E (t means the amounts of transpiration) and the seasonal changes of τ(τ means t/E/ln×10⁴), it was presumed that two peaks for t/E during irrigation period would probably be found for the case of ln.
Total evapo-transpiration amounts throughout the irrigation period varied annualy from 440mm to 553mm and were 493mm on the average, showing 1.22 times as much as E. The average transpiration amount was found to be 0.45 times as much as the evapo-transpiration. The annual changes for the average transpiration amount were larger than the cases of the evaporation amounts obtained from the paddy field.