Characteristics of Soil Crusts and their Influence on Some Soil Properties in Mukogodo Catchment, Kenya

Physical and chemical properties of soil surface crusts formed on overgrazed bare ground, in Mukogodo catchment in Kenya were investigated. These were compared with those of underlying soils and of adjacent grass and bush covered topsoils. Crusting effects on infiltration, hydraulic conductivity and water content were also investigated. The crusts were moderately strong to strong with a thickness of 1-5 mm. Crusts had higher amounts of sand, silt and clay than the underlying layer, while their total N was lower and organic C content higher than the underlying layer. On average, the contents of Ca, Mg and Na were higher in the crusts than in the underlying layers. Similarly, soil pH, EC and ESP were higher in the crusts than in the underlying layer. Cation exchange capacity and K were slightly higher in the underlying layer than in the crusts. Infiltration rate, hydraulic conductivity and soil water content in both the rainy and dry seasons in bare ground were significantly lower than those of the bush and grass covered topsoils. Bare ground surface soil bulk density was higher compared to vegetated topsoils and subsurface layers.