On the effect of frost protection of paddy rice by irrigation

Abstract

Our experiment was made in October 10·11 and 26·27, 1954, to see the effectivity of irrigtion for protecting frost injury of paddy rice.Observed elements are as follows: Air temperature (Height: 10, 20, 40, 60, 80, 100cm), Earth-surface temperature, Water temperature of paddy field and stream. Wind velocity (Height: 10, 20, 40, 60, 80cm)Weathers of observed days were clear and calm or light breeze (Table 1). Vertical distribution of temperature are showed in fig. 1 and are ground inversion types have minimum temperature at a height of 20, 40cm on the ground surface of no plant.The effect of irrigation reached about 40, 60cm in height. Air temparature at 100cm on the irrigated paddy field was generally higher than that of the non-irrigation and this reason is unknown. But suppose both temperatures are equally, we can know the effect of irrigation in comparison of air temperature at 100cm with at each height. This result is shown in fig. 2. From this figure it is seen that the effect of irrigation reached 60, 70cm in height.Therefore it is impossible that padddy rice keep perfectly from forming of frost by this irrigation method, but possible by using jointly the smoking or combustion method.