Researches and experiments were carried out as planned in experimental paddy fields, which consist of tilled and paddled fields (conventional) and non-tilled fields, of the marshy heavy soil in Hachiro-gata polder (D14 field).
The results obtained are as follows :
(1) Ground temperature in the experimental paddy fields
Compared with tilled paddy fields, the ground temperature at the depths of 5cm, 10cm, 20cm, 30cm remained high in non-tilled paddy fields during the cultivation period. Especially, high temperature in the non-tilled paddy fields was favorable for the early growth of rice during the period of rice planting to taking root.
(2) Oxidation reduction potential (Eh) in soil layr
Compared with tilled paddy fields, the values of oxidation reduction potential (Eh) at the depths of 3.5,10,17.5,25,40cm remained high in non-tilled paddy fields during the ponding irrigation period. It shows that soil layrs in non-tilled paddy fields were more oxidized than those in tilled paddy fields.
Density of iron (Fe) and Manganese (Mn) in descent percolation water
The density of iron (Fe)in decent percolaton water was higher in upper plow layr than that in subsoil. Especially, the density of iron (Fe) in tilled paddy fields was higher than that in the non-tilled paddy fields. The density distribution of manganese (Mn) showed the same tendency as that of iron (Fe).
(4) Electric conductivity (EC)
The electric conductivity (EC) in descent percolation water in tilled paddy fields were higher than that in the non-tilled paddy fields at the depth of 3.5cm. EC in the non-tilled and tilled paddy fields tended to rise at the depth of 40cm.
(5) Density of SS (suspended solid) in water on the paddy field and farm drain
The density of SS after rice planting in water on the paddy field and farm drain of non-tilled and tilled paddy field were 20.8mg/l, 78.4mg/l, 28.8mg/l and 159mg/l respectively.
(6) Water requirement rate (water requirement in depth)
Water requirement rate of the non-tilled and the tilled paddy field were 12.6mm/d and 5.7mm/d respectively during the ponding irrigation period. Less