Effects of prolonged sewage irrigation on some physical properties of sandy soil

Abstract

Nine soil profiles were taken from El Gabal El Asfar Farm, 25 km north-east of Cairo. Eight of them represented soils irrigated with sewage water for 5, 10, 20, 30, 40, 50, 60 and 70 years, where citrus trees are grown. The remaining profile was from a virgin area. Soil texture, CaCO 3, organic matter and cation exchange capacity were determined. There were no marked variations in soil texture with sewage application up to the tenth year; thereafter, the texture changed from sandy to loamy-sand in the upper soil layer after 40 years, but subsequently in the upper and subsoils up to the seventieth year. Soil organic matter and cation exchange capacity gradually increased with sewage application. CaCO 3 in soils gradually decreased in the upper layers and increased in the subsoils. Accordingly, prolonged irrigation with sewage water, up to 70 years, improved the soil texture and increased both cation exchange capacity and organic matter content.