To attempt to reveal how to release manganese the soils which have intensively accumulated just under the top soil layer during these soils have been cultivated as paddy, and how to absorb pasturage crops soil manganese, the experiments on the elution of manganese from the soil and of pot cultures, using the soil with accumulated manganese, were performed.
1) Amounts of manganese eluted from the soil increased with increasing of hydrogen ion concentrations of soil or of eluting solutions, however, amounts of iron had kept fairly constant with changing of pH of eluting solution.
2) Concentrations of manganese in pasturage crops had a high correlation with increasing of amounts of soil manganese released, that is, increased with decreasing of soil pH.
3) The existence of phosphrous (ortho-phosphate ion) in the eluting solution lowered the releasing of manganese from the soil, however, when the soil was reduced by addition of reducing agents such as hydroquinone, the effect of phosphorous was scarcely recognized.
4) The soil reduced by addition of easily digestable organic matter such as starch or reducing agents such as hydroquinone was forced to release more manganese than the soil in the more oxidized state, and supplied more manganese to pasturage crops.
5) Application of phosphorous fertilizer to the soil with accumulated manganese improved yields of pasturage crops and decreased the absorption of manganese by pasturage crops, resulting in lowering concentrations in them.