AEOLIAN PARTICLE INPUT TO THE SOIL SURFACE AT THE NORTHERN LIMIT OF THE NEGEV DESERT

In arid and semiarid regions, aeolian particle input is one of the maj or sources of soil nutrients. The particle input also improves the soi l depth and strongly influences the water-holding capacity of the soil . The authors studied the airborne particle accumulation dynamics on t he soil surface in the Northern Negev desert (Sayeret Shaked Park) in comparison to the Central Negev highland (Sede Boqer and Shivta). The measurements of the components of the aeolian deposition and accumulat ion at the study site of the Sayeret Shaked Park were carried out for 3 years from August 1992 to July 1995. The average soil accumulation f or this period was 0.22 g m(-2) d(-1) (80.64 g m(-2) year(-1) The mini mal quantity during the research period was during July 1993 (1.35 g m (-2) month(-1)) and the maximal was in March 1993 (24.42 g m(-2) month (-1)). Significant differences were obtained during the whole study pe riod regarding the slope directions of the watershed. The aeolian accu mulation and the deposition on the north-facing slope was significantl y lower (P < 0.05) than on the south-facing slope (average 5.09 g m(-2 ) month(-1) to 6.97 g m(-2) month(-1), respectively). The highest accu mulation was obtained in the wadi (average 8.27 g m(-2) month(-1)). Al most all the granulometric analyses conducted on monthly collected sam ples for the study period showed significant amounts of clay-size (<16 mu m) and silt-size (between 16 to 50 mu m) particles. Chemical compo sition of the airborne particles showed that two major constituents, S i and Ca, dominate all the samples. Particle-size analysis of the aeol ian particles accumulated during the study period at the Sayeret Shake d area showed a median diameter varying between 25 and 35 mu m. This l ends to a layer of fine airborne particles or loess, as scattered silt or clay particles, of 14 mu m m(-2) year(-1).