Abstract
Winter rye was grown on an experimental paddy field and in spring, before transplanting rice, it was ploughed into the soil at the rate of 246-600 kan per tan. To the control plot, ordinary compost manure was applied at the rate of 300 kan per tan instead of rye plants. The field was leaky, its subsoil being "Awasuna", a kind of sand. The resluts were as follows : In the years of warmer seasons, the growth of the rice plant on the rye plots was slower than that on the compost plots, while no signifcant differences in yield were found between them. In the cooler years (1053 and 54), however, the heading times on the rye plots were conversely 8-9 days earlier than those on the control ones, and the yields fronm the formers were 98-149 % heavier than those from the latters. The correlation between the temperatuer during the growth period and the increment of yield due to the rye application was very high (1, 946). According to the result of an experiment performed in 1954, it was elucidated that the difference in water temperature between the rye plot and the cotrol compost plot was not large during daytimes, while at night, it was higher in the rye plot, the irrigation water requirement being reduced in the rye plot to almost a half of that in the control plot. In this year, the yield of the rye plot increased by 325 % of that of the control. The main reason for such favorable effects of rye application on rice crops in cooler seasoned years may be that the rye plant ploughed in the soil should have controlled the water percolation to some extents and kept consequently the water temperature fall at night within a narrower range than that in the ordinary field supplied with ordinary compost manures.
