Assessment of soil erosion by water on agricultural slopes in Poland based on runoff plot measurements

This paper presents soil erosion measurements that were conducted between 2007 and 2009 on runoff plots under bare fallow and typical crop cultivations (cereals, root crops) across five regions of Poland representing diverse climatic and soil conditions. The aim of the research was to estimate the water erosion in these regions using a standardized method (runoff plots) and empirically by determining key parameters of the (R)USLE model: rainfall erosivity (R-factor), soil erodibility (K-factor), and cover management (C-factor). Rainfall erosivity during the study period exhibited considerable variability. The most extreme erosive rainfall event was recorded in southern Poland (907 MJ mm ha⁻¹ h⁻¹, Łazy). Seasonal distribution and rainfall intensity reflected regional climatic conditions. The study showed that soil erosion by rainfall exceeded that resulting from snowmelt. The average runoff coefficient varied annually from 0.24 % (cereals, sandy soil) to 10.5 % (fallow, silt loam). The mean annual soil loss rate (SLR) from bare fallow plots ranged from 2.5 to 73 Mg ha⁻¹, the lowest on sandy soils and highest on silt loam. Under beet and potato cultivation, soil loss rate was approximately 40 % lower and over 90 % lower under cereal crops than in the bare fallow. Grass cover nearly completely prevented soil erosion. Across all study areas, the highest erosion occurred from May to June. Discrepancies between empirically derived equation parameters and those calculated using the (R)USLE model highlight the necessity for regional model validation. SLR obtained in the study areas, using direct measurements and the (R)USLE model, fall within the range of estimates projected for European conditions.