Effect of soil texture and CaCO₃ content on water infiltration in crusted soil as related to water salinity

The effect of soil texture and CaCO₃ content on water infiltration rate in crusted soil was studied with the use of a rain simulator. Two types of soils with low exchangeable sodium percentage (ESP < 3.0%) were studied: (i) calcareous soils (5.1-16.3% CaCO₃) with a high silt-to-clay ratio (0.82-1.47) from a region with < 400 mm winter rain; and (ii) non-calcareous soils with a low silt-to-clay ratio (0.13-0.35) from a region with > 400 mm winter rain. Soil samples with clay percentages between 3 and 60 were collected in each region. Distilled water (simulating rainfall) and saline water (simulating irrigation water) were sprinkled on the soil. The soils were exposed to 'rain' until steady state infiltration and corresponding crust formation were obtained. For both types of soils and for both types of applied water, soils with ∼ 20% clay were found to be the most sensitive to crust formation and have the lowest infiltration rate. With increasing percentage of clay, the soil structure was more stable and the formation of crust was diminished. In soils with lower clay content (< 20%), there was a limited amount of clay to disperse and, as a result, undeveloped crust was formed. Silt and CaCO₃ had no effect on the final infiltration rate for either type of applied water, whereas with saline water, increasing the silt content increased the rate of crust formation.