Abstract
In the paddy field being irrigated continuously with cold water, horizontal distribution of both water and soil temperature at nine points and vertical distribution of air temperature at three points, i.e. water inlet, center and water outlet, were measured on a clear day in July and August, 1952.The results obtained are as follows:1) On a sunny day in summer, cold water (14-20°C) is warmed up strikingly in the paddy field, although the sunlight is restricted by the plant cover. On 27th of July, for example, water temperature of 34°C was observed at the water outlet.2) In each figure of horizontal distribution of water and soil temperature for every hour, isothermal lines are represented by concentric circle with the center at the inlet.3) Diurnal movement of isothermal lines in those figures has a interesting periodicity, and between 10 and 15m from the inlet there is a noteworthly zone showing the maximum of rising up of water temperature.4) Diurnal changes of vertical temperature distribution at three points with different water temperature are shown in fig. 4. This figure show that types of vertical distribution of temperature in paddy field are closely related to size and density of rice plant and are modified remarkably by water temperature The nfluence of water on the temperature of air layer above it is found to be higher in night than in day time, and the height of influence goes up with growth of the plant.
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