Measurement of saturation overshoot under grass cover

The paper deals with non-destructive measurement of water infiltration into homogenous soil (Haplic Chernozem) covered by grass. The experimental site was located in Most pri Bratislave (Slovakia) in the Pannonian Basin at a height of 130 m above sea level. Radioactive tracer technique was used to determine the water content of the soil profile during water infiltration. A mixture of the radioactive iodine I-131 (chemical form (NaI)-I-131) and the NaI solution was used as a tracer. The tracer distribution in the soil was measured by the Geiger-Muller detector connected to the nuclear analyser. Gravity-driven fingers were detected in the soil under the grass cover as a consequence of the wetting front instability. The instability manifested itself as a non-monotonic moisture profile caused by saturation overshoot and a varying discharge from the soil profile in time.