中海干拓地農業への都市下水利用に関する基礎的研究(III) : 都市下水処理汚泥による土壌改良と作物栽培

Large scale experiments on the improvement of soil with municipal sewage sludges and on the cultivation of crops such as Italian ryegrass, tulip, and tomato for processing (two varieties of Kagome-70 and Super Roma VF) were carried out at a farm-land in the reclaimed land of Iya from April of 1978 to August of 1979. The farm-land was divided into three parts : In each division, soil above a depth of 15 cm was neutralized by the addition of 5 or 10 wt. % of municipal sewage sludge or 1 wt. % of calcium carbonate. Although the soil retained around neutral or weakly alkaline pH throughout 1978, significant acidification was observed at the lime and 5% sludge divisions from January to February of 1979. No appreciable acidification occurred during the experimental period at the 10% sludge division. The 10% sludge division was markedly superior to the lime division in cultivation experiments, too. That is to say, the yield of crops in the 10% sludge division was higher than that in the lime division by a factor of ca. 2.0 for Italian ryegrass, 1.3 for tulip, 2.6 for tomato (Kagome-70), or 4.7 for tomato (Super Roma VF). It was presumed that the kind and concentration of phosphate salts in soil, as well as pH of soil, are important factors which affect the growth of crops in the reclaimed land.