Slope position and management practices as factors influencing selected properties of topsoil

An interaction between the slope position and type of soil management practices could be one of the most important factor affecting several soil properties including soil structure. Therefore, we evaluated selected soil properties including soil structure parameters in relation to slope gradient and soil management practices between Trakovice and Bue'any villages (western Slovakia). The sampling sites were located in two adjacent, gently sloping fields with a NW-SE orientation. The sites also differ in soil management type: Field No. 1 was used as arable land with intensive cultivation (IC) of crops, while a greening system (GS) had been established on Field No. 2. Soil samples were taken from five geomorphological zones at each slope: summit, shoulder, back-slope, toe slope and flat terrain under the slope. Results showed that soil pH, content of soil organic matter (SOM) and carbonates depended on land use of the slopes. In GS, the water-stable macro-aggregates (WSA(ma)) 0.5-3 mm (favourable size fraction) displayed statistical significant quadratic polynomial trend along the slope gradient. In IC the values of mean weight diameter of dry sieved aggregates (MWDd) decreased significantly along the slope gradient, while in GS the opposite trend was observed. In IC significant correlations between carbonates content (r=-0.775, P<0.01), humic acids (HA) content (r=0.654, P<0.05), colour quotients of humic substances (r=-0.706, P<0.05), colour quotients of HA (r=-0.723, P<0.05) and MWDd were determined. In GS higher content of carbonates was followed by a decrease in content WSA(ma), MWDd, mean weight diameter of wet sieved aggregates (MWDw) and stability index of aggregates. At the same time stabile and labile soil organic matter improved soil structure parameters in GS.