中海干拓地農業への都市下水利用に関する基礎的研究(II) : 干拓地土壌への都市下水処理水および汚泥の還元について

Soil, which was collected from the reclaimed land of Iya and packed in lysimeters in January of 1977, showed an abrupt acidification in the summer and then it recovered in pH above 5.0 in the following spring. However, the pH of soil again rapidly decreased in the successive summer. The concentration of the chloride ion in soil steadily decreased to the extent that there may be no problem for the growth of the crops. The cultivation of land was effective for the acceleration of the oxidation of oxidizable sulfur. The application of municipal sewage effluents to the reclaimed land soil revealed that the soil has a strong nitration action on ammonia together with a strong adsorption action on phosphate. The Langmuir adsorption isotherm virtually held for the adsorption of phosphate on the soil. The adsorption equilibrium constant was decreased by the coexistence of ionic species in solution. Municipal sludge is very effective for the improvement of soil in the reclaimed land. Although a significant amount of cadmium was detected in the sludge, the amount of cadmium absorbed in vegetables, grown in the presence of the sludge, was slight. It is important to consider the method for draining from a farm-land in order to cultivate a vegetable.