Soil erosion is the most widespread problem in soil management. It leads to changes in the properties of soil horizons, which in turn can also affect the pace of slope processes. This may be signifi cant problem in young morainic areas where truncation of clay-illuvial soils (Luvisols, Retisols) transforms both the organic carbon content and texture of arable horizons. Changes in soil susceptibility to erosion can be measured using the soil erodibility factor (K) widely used in erosional models. The aim of the submitted study is a calculation of the erodibility factor (K) for soils represented different stages of truncation in a hummocky landscape of Northern Poland. Erodibility factor was calculated using the formula of the Erosion Productivity Impact Calculator (EPIC) model. For assessment of the factor, soil profi les were divided into four groups, varying degrees of soil truncation: completely eroded, strongly eroded, slightly eroded and non-eroded arable soils, noneroded forest soils. In the course of the performed study, it was noted that the soil erodibility K factor values were between 0.0172-0.0352 t•ha•h•ha -1 •MJ -1 •mm -1 and depended on the stage of soil truncation. Properties of surface horizons of completely eroded soils accelerate erosion about 6% compared to strongly eroded and 12% to slightly eroded soils and even 48% as against non-eroded forest Luvisols/Retisols. The main factors affecting erodibility growth in truncated profi les was a revealed decrease in both -ccarbon content and sand fraction in humus horizons. Susceptibility to erosion was also increased by exposure of Bt or C(k) horizons richer in clay fraction.

Aggregate stability is a crucial factor in predicting the development of the erosion process, and it is particularly important in landscapes with high heterogeneity of soil cover, such as young hummocky moraine uplands. The objective of the presented work was to estimate the influence of erosion on the properties of aggregates and analyze the variation of aggregate stability under different erosion-related alterations of soil cover. The conducted research indicates that erosion has led to a deterioration of the quality of soil structure in the upper parts of the slopes, which in turn may intensify the slope processes leading to faster truncation of the pedons. Both the differentiation of the soils themselves and the stability of the aggregates were very strongly linked to erosive transformations. The tops of the hills and the upper parts of the slopes are covered with completely or strongly eroded soils in which the aggregates have the least favorable characteristics. Due to the smallest amount of humus and the highest clay content, the soils have the largest share of soil clods, which are aggregates larger than 7 mm that may have formed in dry conditions (soil drought). The plow horizons of most eroded Eutric Regosols and strongly eroded Luvisols have very poor water resistance, similar to that of the subsoils. The main factor determining the low aggregate stability of Eutric Regosols is the number of secondary carbonates that lead to a rise in soil dispersion. Strongly eroded Haplic Luvisols have a low resistance to water due to relatively high clay content (20–26 percent). The higher stability of aggregates in soils with colluvial materials (Albic Luvisols, Mollic Gleysols, Endogleic Phaeozems) depends mainly on soil organic carbon content. The results showed the necessity for adaptation of land management practices to .real condition and heterogeneity of soil cover.

Soil erodibility is one of the crucial parameters for modelling soil erosion, expressed as the K-factor. The presented study tries to illustrate the spatial variance of K-factor on a local scale through the investigation of soil properties and descriptive spatial analysis utilising GIS tools at microscale in a young hummocky moraine landscape in Northern Poland. The results of the interpolation of K-factor values illustrate their changing from high values in eroded pedons on the tops of hummocks to low values in kettle holes. The middle position is occupied by slightly and non-eroded pedons. The mean weight results were very similar to data that were found on the scale of Europe and Poland. In landscapes with heterogeneous soil cover, there are significant differences in maps based on different approaches to data visualisation. There are advantages and disadvantages to both (1) referring to mean values of the K index for soil contours representing different soil types and (2) interpolating the values obtained from individual points (GIS tool). Interpolation can be used for a thoroughly examined area with a high number of input points, while a map based on mean K index values for soil contours would be more effective in homogeneous areas.

No abstract

Slaking is a rapid wetting of soil aggregates that affects their stability in the face of the effects of water. The aggregate’s stability has an indirect influence on soil functioning through its minimising of soil erosion. Testing slaking is very simple, does not need additional complicated equipment and could be done for any point. Testing was performed for natural air-dry aggregates (7–10 mm) sampled from the arable layers of four different types of soils within a young hummocky moraine landscape: Eutric Regosol (Protocalcic), Haplic Luvisol (Protocalcic), Albic Luvisol, Mollic Gleysol. The soil tests were performed on a soil-erosive catena located in Chełmno Lake District (Northern Poland) from the tops of hummocks and from the shoulder to bottom part of depressions. The test results demonstrated a significant decrease in aggregate stability from Mollic Gleysol to Eutric Regosols (Protocalcic) – that is, from colluvial soils at depressions to completely eroded hummock-top soils. However, 75% of all aggregates in Eutric Regosols were unstable when time of aggregate destruction was less than 300 sec. Oppositely to Eutric Regosols laying on hummock tops, 70% of aggregates of Mollic Gleysols in depressions were water stable. The mean time for aggregate destruction for each soil from hummock-top to depression was 209 sec. for Eutric Regosol, 375 sec. for Haplic Luvisol, 616 sec. for Albic Luvisol and 772 sec. for Mollic Gleysol. The main soil properties that affected the time of aggregate destruction are clay content (very strong negative correlation; r=–0.72); soil organic carbon content (strong positive correlation; r=0.69), and content of secondary carbonates (strong negative correlation; r=–0.69).