Relationships between moisture penetration and salinity in soils of the northern Negev (Israel)

Abstract

The moisture regimes and salinity status of soils of different textures found on various topographic positions in the Be'eri badlands (northern Negev) were examined. The soil moisture regime was determined by frequent moisture and salinity determinations during a normal year (280 mm rainfall) and during an exceptionally wet year (597 mm rainfall).A close relationship was found between the soil ESP and EC values and the depth of water penetration in the various soils. ESP values increase gradually with depth until a somewhat saline layer with EC values of 2 or 3 is reached. ESP values of 10 correspond approximately in most soils with the depth of water penetration in a normal year, and the beginning of the saline layer corresponds with depth of water penetration in a wet year.Water penetration in the coarse-textured sandy Regosol (Typic Quartzipsamment) and Husmas (Typic Xerothent) soils was deep even in the normal year, with salts leached out to the groundwater and ESP values relatively low.Water penetration in the medium-textured cumulic light Brown loam and the loessial light Brown soils (Mollic Calcic Haploxeralfs) reached a depth of about 1 m in the normal year. In the rainy year water penetration reached a depth of more than 2 m.In the fine-textured natric grumic dark Brown soil (Vertic Natrargid) on moderate slopes and nonsaline clayey Regosol (Typic Xerothent) on steep north-facing slopes, water penetration in the normal year reached a depth of about 80 cm, and in the rainy year it reached 150 to 170 cm.Water penetration in the clayey saline Regosol (Vertic Torriorthent) reached only 30 cm even during the rainy year. This soil is saline already at a shallow depth due to this restricted water penetration.The moisture regimes of most soils of the Be'eri banlands are xeric, although those in the loessial light Brown clay loam and the grumic natric dark Brown clay border the aridic soil moisture regime. A typical aridic soil moisture regime characterizes the saline clayey Regosol.A close relationship also exist between soil moisture regime, natural vegetation and success of dryland agriculture. Measurements of EC and ESP values may thus enable evaluation of the long-term soil moisture regime and success of dryland agriculture in similar mildly arid areas.