Variability of Infiltration in a Field with Surface-sealed Soil

Ben-Hur, M.; Shainberg, I.; Morin, J.

Variability of Infiltration in a Field with Surface-sealed Soil

1987

Ben-Hur, M. | Shainberg, I. | Morin, J.

The infiltration rates (IR) for water were measured at 30 random sites within a 1-ha field by sprinkler and flood infiltrometers. A portable rainfall infiltrometer was used to measure the infiltration rate under water-drop impact conditions, and double-ring infiltrometers were used to measure IR in flooded conditions. No spatial dependence of the steady-state IR values measured with the two methods was found. The mean steady-state IR measured with the flood infiltrometer was 57.8 mm h⁻¹ with a coefficient of variation (CV) of 41.8%. The mean steady-state IR measured with the sprinkler infiltrometer was 8.6 mm h⁻¹ with a CV of 14.7%. This difference was due to the formation of a soil surface seal from the impact of falling drops. The seal's hydraulic conductivity was much lower and less variable than that of bulk soil. Frequency distributions of the steady-state IRs measured with the two methods were different; that from the double-ring infiltrometer had a small deviation to the left, while that of the sprinkler infiltrometer had a large deviation to the right. The distribution of steady-state sprinkler IR values corresponds with the distribution in the cation exchange capacity (CEC) and exchangeable sodium percentage (ESP) in the field, verifying the known dependence between surface seal formation and the soil CEC and ESP relationship. This dependence was not found for the IR values measured by flooding. No correlation was found between the IR values measured by the two methods. Thus, for soils that seal, it is impossible to predict IR under water drops from measurements under flooding conditions.

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