אסיף מאגר המחקר החקלאי

Effect of water quality and amendments on the hydraulic properties and erosion from several mediterranean soils

Year:

1991

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Volume :

4

Co-Authors:

Shainberg, I., Institute of Soils and Water, ARO The Volcani Center, P.O. Box 6 Bet Dagan, Israel
Gal, M., Institute of Soils and Water, ARO The Volcani Center, P.O. Box 6 Bet Dagan, Israel
Ferreira, A.G., University of Evora Apartado 94 7001 Evora Codex Portugal
Goldstein, D., Institute of Soils and Water, ARO The Volcani Center, P.O. Box 6 Bet Dagan, Israel

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Abstract:

The response of six sandy-loam soils from Portugal and Israel to leaching with sodic and saline water and to simulated rain was studied. The dominant clay mineral in the soils from Portugal was kaolinite, whereas smectite predominates in the soils from Israel. The permeability of the soils depended on the soil texture: it decreased with an increase in the silt and clay content. The response of the soils to sodicity depended on the electrolyte concentration; salt concentrations exceeding 10 mmolc·L-1 was enough to prevent the deleterious effect of exchangeable sodium (≤20%). When leaching with distilled water (stimulating rain water), the presence of primary minerals and lime determine the susceptibility of the soils to sodicity. The calcareous loess from Israel was the least susceptibility to sodicity. The six soils were susceptible to sealing, high runoff and erosion when exposed to rain. The soil surface was particularly vulnerable to sealing due to both the mechanical impact of raindrops and the low concentration of electrolytes in the rainwater. Seal formation was due to two mechanisms: 1. (i) physical disruption of aggregates at the soil surface which depended on the impact energy of raindrops and the inherent aggregate stability; and 2. (ii) chemical dispersion which depended on the mineralogy of the clay, the ESP, and the electrolyte concentration. When the impact of the drops was prevented, or when the anionic polymer was sprayed at the soil surface, physical breakdown of the aggregates was reduced and runoff and erosion were slight. When the electrolyte concentration was high, the chemical dispersion was small and runoff and erosion decreased, compard with the control. The smectite soils from Israel were more susceptible to sealing than the kaolinitic soils from Portugal. © 1991.

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