Effects of flood irrigation and plant growth on two riverine soils

Abstract

Two soils which contained significant proportions of exchangeable sodium were frequently irrigated during summer with water of low electrolyte content. When all vegetation was removed the soils became very unstable in water. When the natural vegetation was left intact the stability and structure of the soils did not deteriorate despite frequent irrigation. When the amount of vegetation was increased by sowing Rhodes grass (Chloris gayana Kunth) and supplying nitrogen and phosphorus the stability of the soil increased. After 8 years' growth of Rhodes grass the top inch of soil contained 30–40 per cent. of water-stable aggregates greater than 1 mm in diameter, compared with a content of 10–20 per cent. in virgin soil. Thus, the protective effect of the organic matter added to the soil by plant growth more than compensated for aggregate disruption caused by flood wetting or by a reduction in electrolyte content of the soil solution.