Infiltration rate measurements in arid soils with surface crust

The effects of infiltrometer type and water application rate on infiltration were studied for a crust-forming soil at the University of Jordan Research Station near Al-Muwaqqar village. The total amount of water applied in all cases was 38 mm. The highest infiltration rate values occurred in basin infiltrometers followed by sprinkler and furrow infiltrometers. The infiltration rate at the end of water application decreased significantly by 41-57% with decreasing application rate from 28.4 to 6.2 mm/h regardless of infiltrometer type. Increasing the initial soil oar moisture content decreased the infiltration rate by about 4-11% in all infiltrometer types and application rates. In the basin infiltrometer, lateral water movement occurred all around the basin borders, thus increasing the measured basic infiltration rate. In the furrow infiltrometer, the for formation of a sedimentary crust on the furrow bottom reduced the basic water infiltration rate to 3.6 mm/h. The wetted zone formed with the sprinkler infiltrometer reduced lateral water movement, and the measured basic infiltration rate was close to the basic infiltration rate measured by the double-ring infiltrometer. The measurements were used to establish infiltration rate curves and equations. In a second experiment, the Stirk correction significantly reduced the water lateral divergence factor by 27.1% in single-ring infiltrometers. The Stirk correction factor was different in single- and double-ring infiltrometers. Thus, the basic infiltration rate was 4.8 and 3.5 mm/h using the single and the double infiltrometers, respectively, while the corresponding correction factors were 0.67 and 0.91, respectively. The corrected infiltration rate was only 3.2 mm/h, which confirms the tendency of these crusted soils to generate huge runoff at even small application rates.