Volume XV |

The Influence of Extreme Rainfall on Flow, Soil Moisture, Nutrients and Tracer Pathways

Abstract: On two agricultural experimental catchments with different vegetation cover we have carried out experiments with leaching or wash off nutrients due to high artificial rain intensities: grassland after grazing, arable land, river bank covered with grass and during different seasons (spring, summer, autumn). Rainfall total and soil moisture have been automatically recorded in two depths. The concentration of nutrients was analysed in the laboratory. From the results, it is possible to formulate the following conclusions: flow of nutrients during extreme precipitation is high at the beginning of the soil profile saturation and then gradually decreases; increasing concentration occurs in the period just after grazing or after fertilisation with manure; the highest concentration of nutrients occurred in experiments on the field after tillage. The outcomes correspond to results from rainfall-runoff events, when extreme rainfall causes the wash off the soil into the stream. Before and after the experiment the samples of soils have been taken. The change in POlsen (Olsen P) on the pasture slope was less than 1 mg/kg of dry matter of soil while on the catchment used for crops it was larger than 10 mg/kg. Understanding flow pathways in a catchment requires carrying out field experiments with conservative tracers. The contribution brings results from such experiments on a meadow and in forest. Both types of field experiments with sprinkling contribute to the understanding of the flow and nutrient pathways during an extreme rainfall.