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Erosion is a severe threat to the sustainable use of agricultural soils. However, the structural resistance of soil against the disruptive forces steppe soils experience under field conditions has not been investigated. Therefore, 132 topsoils under grass-and cropland covering a large range of physico-chemical soil properties (sand: 2-76%, silt: 18-80%, clay: 6-30%, organic carbon: 7.3-64.2 g kg À1 , inorganic carbon: 0.0-8.5 g kg À1 , pH: 4.8-9.5, electrical conductivity: 32-946 μS cm À1 ) from northern Kazakhstan were assessed for their potential erodibility using several tests. An adjusted drop-shatter method (low energy input of 60 Joule on a 250-cm 3 soil block) was used to estimate the stability of dry soil against weak mechanical forces, such as saltating particles striking the surface causing wind erosion. Three wetting treatments with various conditions and energies (fast wetting, slow wetting, and wet shaking) were applied to simulate different disruptive effects of water. Results indicate that aggregate stability was higher for grassland than cropland soils and declined with decreasing soil organic carbon content. The results of the drop-shatter test suggested that 29% of the soils under cropland were at risk of wind erosion, but only 6% were at high risk (i.e. erodible fraction >60%). In contrast, the fast wetting treatment revealed that 54% of the samples were prone to become "very unstable" and 44% "unstable" during heavy rain or snowmelt events.Even under conditions comparable to light rain events or raindrop impact, 53-59% of the samples were "unstable." Overall, cropland soils under semi-arid conditions seem much more susceptible to water than wind erosion. Considering future projections of increasing precipitation in Kazakhstan, we conclude that the risk of water erosion is potentially underestimated and needs to be taken into account when developing sustainable land use strategies.In memory of Yves Le Bissonnais and his efforts in establishing a standardised method to determine aggregate stability.

<p>After extensive research on different methods to measure<strong> particle size distribution</strong> (PSD), soil scientists are proposing the<strong> laser diffraction method</strong> (LDM) as a standard method for soil texture analysis. However, the effects of different pretreatments on particle size analysis of dry steppe soils with LDM has not been tested so far. This study aims to evaluate <strong>different pretreatment methods</strong> with the purpose to disperse aggregates and remove binding agents in <strong>Chernozem and Kastanozem</strong> soils. To cover a wide range of different land-use types and farming methods, 112 surface soil samples were taken from 13 fields on four different test sites in <strong>Kazakhstan</strong>. Before LDM analysis, all samples were pretreated with either H<sub>2</sub>O<sub>2</sub> to remove organic carbon or HCl to remove carbonates. The results showed that removing organic matter with H<sub>2</sub>O<sub>2</sub> led to complete sample dispersion while HCl pretreatment caused incomplete dispersion, likely due to aggregation by calcium ions released by the dissolution of carbonates.</p>

<p>Erosion caused by extreme climate conditions and intense agricultural use is a severe threat to the soil quality of dry steppe ecosystems. The susceptibility of soil to erosion depends mainly on the stability of its structure against mechanical stress, which is directly related to the stability of aggregates. However, there is no generally accepted method to determine soil aggregate stability and most tests cannot be adequately linked to disruptive forces soils experience under field conditions. Thus, our main objective was to explore the aggregate stability of steppe soils against disruptive stresses by wind and water to assess their potential erodibility. We examined 132 topsoil samples from northern Kazakhstan under two land-use types (grassland and cropland), covering a large range of physico-chemical soil properties (texture, organic carbon, inorganic carbon, pH, and electrical conductivity). We combined several methods that capture the soil`s susceptibility against mechanical stresses common in the dry continental climate: An adjusted drop-shatter technique (energy input of 60 Joule) was used to estimate the stability of dry soil against weak mechanical forces, such as wind stroking over bare soil after tillage and before crop emergence. In addition, three wet-aggregate stability tests (fast wetting, slow wetting, and wet mechanical breakdown) were used to estimate the stability of soil aggregates under various stresses caused by precipitation. Results indicate that aggregate stability was generally higher for grassland than cropland soils. Aggregate stability under both land-use types decreased along with increasing sand and decreasing organic carbon contents. The drop-shatter method suggested that only 5% of cropland soils were at high risk of wind erosion (i.e., erodible fraction <60%). In contrast, the fast wetting test revealed that  98% of the samples are unstable after a heavy rain event or snowmelt. Even after a light rain event or the raindrop impact, 54-58% of the samples were unstable and prone to erosion.</p><p>We conclude that cropland in the dry steppe of Kazakhstan is much more vulnerable to the disruptive forces caused by water than by wind. Especially the severe breakdown of aggregates during heavy rain events or snowmelts goes well in line with the increasing erosion risk under current and future climate scenarios.</p>