Abstract
Exact estimates of soil clay (<2 μm) and silt (2–20 μm) contents are crucial as these size fractions impact key soil functions, and as pedotransfer concepts based on clay and silt contents are becoming increasingly abundant. We examined the effect of removing soil organic matter (SOM) by H2O2 before soil dispersion and determination of clay and silt. Soil samples with gradients in SOM were retrieved from three long-term field experiments each with uniform soil mineralogy and texture. For soils with less than 2 g C 100 g-1 minerals, clay estimates were little affected by SOM. Above this threshold, underestimation of clay increased dramatically with increasing SOM content. Silt contents were systematically overestimated when SOM was not removed; no lower SOM threshold was found for silt, but the overestimation was more pronounced for finer textured soils. When exact estimates of soil particles <20 μm are needed, SOM should always be removed before soil dispersion.
Highlights
Reliable estimates of clay- (
Bulk soil (6–15 cm depth) was sampled in autumn 2014 from four different fertilization treatments in a field grown with a 4-year crop rotation (winter wheat (Triticum aestivum), silage maize (Zea mays), and spring barley (Hordeum vulgare) undersown with a grass-clover mixture that is used for cutting in the subsequent production year) [20]
The soils at Bad Lauchstadt and Askov ranged from 1.63–2.57 and 0.87–1.41 g C 100 g-1 minerals, respectively, with the smallest soil organic carbon (SOC) content under the unfertilized treatments and the highest under the treatments receiving the highest
Summary
Reliable estimates of clay- (
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