Water infiltration and redistribution within soils affected by a surface crust

The effects of soil surface crust and sand columns (pits) on water infiltration and distribution were studied in soils affected by surface crust. Field experiments were conducted during 1994/95 and 1995/96 at Al-Muwaqqar watershed. Changes in soil water content for the natural soil profile as affected by rainfall were studied for five sites at Al-Muwaqqar watershed. Also, field experiments were conducted during 1995/96 and 1996/97 at the University of Jordan Research Station near Al-Muwaqqar village to investigate the effects of sand columns, sand columns spacing and soil ridges on soil water content and redistribution. In the natural soil profile, soil water content changed with time according to rainfall amounts and the interval between rainfall storms. For the 0-20 cm surface layer, maximum soil water content of 233 mm m(-1) occurred on 11 December 1994 with a total rainfall range from 72.2 to 92.2 mm. The maximum changes in soil water content were 198.5 and 159.0 mm m(-1) during 1994/95 and 1995/96, respectively. However, for the 20-40 cm depth, soil water content changes were less sensitive to rainfall amounts compared to soil water content changes in the 0-20 cm layer. Maximum changes in soil water content were 61.0 and 108.5 mm m(-1) for layer 20-40 cm in 1994/95 and 1995/96, respectively. Also, there were no significant changes in soil water content for layers 40-60 and 60-80 cm. The maximum changes were 17.5 and 11.5 mm m(-1) for layers 40-60 and 60-80 cm, respectively. The negligible changes in soil water content for layers 40-60 and 60-80 cm during winter were due to the low rainfall amount, and the very low soil surface infiltration and permeability owing to the surface crust formed after any wetting. Using sand columns within a plot completely surrounded by soil ridges increased moisture stored in the deep layers. Decreasing sand column spacing increased infiltration and moisture stored in the soil profile. After a 21.4 mm rainfall event the moisture stored in the deep layer (30-60 cm) ranged from 5.03 to 8.01 mm. Thus, sand columns with soil ridges might be the best technique to be used for orchards and deep rooted crops. Also, using sand columns without soil ridges resulted in a significant increase in moisture stored in the soil profile and decreased surface runoff. Sand column increased moisture stored in the 60 cm soil profile from 34.5 mm in control treatment to 54.7, 49.8 and 43.4 mm in treatments with 1, 2 and 3 m sand column spacing, respectively. Thus, this technique can be used in forage and field crops production. (C) 1997 Academic Press Limited.