シミュレーションによる酸性硫酸塩土壌の修復処理が稲の生産性に及ぼす影響

Effects of the application rate of basic slag (BS₁₀ and BS₂₀: basic slag 10 and 20 t ha^-1), aggregate size (A₂₀ and A₃₀: aggregate sizes of soils, less than 20 and 20-30 mm) and groundwater level (GW₀: no influence of groundwater and GW₅₀: groundwater beneath 50 cm of the soil surface) treatments on the growth and yield of rice (Oryza sativa L.; BR-3 Mukta) cultivated in two pre-leached (leached for a week through tap water to remove excessive acidity and salinity from the soils before seedling transplantation) acid sulfate soils of Badarkhali (Salidic Sulfaquept) and Cheringa (Typic Sulfic Halaquept) series were evaluated in a simulation study. Optimum growth and yield of rice were recorded by the treatment combining A₃₀GW₅₀BS₂₀ in both the Cheringa (grain: 6.70 t ha^-1) and Badarkhali (5.78 t ha^-1) soils. The application of basic slag (BS₂₀) was found to be the most effective among the individual treatments, followed by the BS₁₀>GW₅₀>A₃₀ treatments. The application of BS₂₀ increased the grain yield in combination with the GW₀ treatment by 100% for A₂₀, while by 122% for A₃₀ in the Badarkhali soil. On the other hand, in the case of GW₅₀, these increments were 138 and 246% for A₂₀ and A₃₀, respectively, in the soils. However, the application of BS at the highest rate (BS₂₀) to the Cheringa soil was not as effective as the A₂₀ and A₃₀ treatments in the Badarkhali soil. On the other hand, the same rate (BS₂₀) of basic slag in combination with the GW₅₀ treatment increased the grain yield by 152 to 382% in the Cheringa soil compared with 138 to 246% in the Badarkhali soil. Almost similar and significant (p≤0.05) effects were observed for the other yield components of rice grown in both soil series. The effect of a larger soil aggregate size (20-30 mm) was more significant on the increase of the growth and yield of rice during the 4-month growing period of rice, regardless of treatments.