中海干拓地農業への都市下水利用に関する基礎的研究(IV) : 都市下水処理汚泥の投与に伴う土壌化学成分の変化

A variety of chemical components were analyzed for soil samples collected from a farm-land in the reclaimed land of Iya over a period from March to June of 1980，the period corresponding to ca. two years after the acid sulfate soils distnbuting in the farm-land were improved by the addition of municipal sewage sludges. Soil improved by the addition of a sufficient amount of the sludge was held at pH 7 or above and was abundant in hot HCl-soluble PO_4-P and Ca-type phosphate enough to maintain the growth of crops. In addition, the cation exchange capacity of the soil and the content of organic matter in the soil were slightly, but appreciably, larger than those for soil improved by the addition of CaCO_3. However, a significant amount of oxi dizable sulfer remained still in the soil, so that a marked lowering of pH was observed for lime deficient soil. Humic acid extracted from the soil was a small quantity and belonged to the Rp-type.