Investigation of Biochar and Slurry Effects On Aggregate Stability As An Index of Soil Erosion Using X-Ray Computed Tomography.

Investigation of biochar and slurry effects on aggregate stability as an index of soil erosion using X-ray computed tomography

Khademalrasoul, A.[1], N. Muhammad, B.V. Iversen, G. Heckrath, L.W. de Jonge, L. Elsgaard

Abstract

It is well known that aggregate stability is influenced by soil organic carbon content. Computed tomography (CT) techniques of intact soil aggregates allow producing reliable 3D images of soil interiors at high resolution. This study aims at investigation the effects of organic carbon on aggregate stability and thereby the erosion potential of the soil. The research was carried out in Denmark in a sandy loam in an experimental design with 12 plots each having different amount of biochar (made from woodchip) and pig slurry applications varying respectively from 10 to 50 and 21 to 42 tons per hectare. In the laboratory, aggregates (1-2 mm, 2-4 mm, 4-8 mm and 8-16 mm) from topsoil (0-10 cm) were analysed in relation to colloid dispersibility and tensile strength. From six selected plots, X-ray CT scanning with high resolution where performed on aggregates at the size of approximately (32-55 mm) and macroporosity (> 80 μm) was calculated with a computer software (ImageJ) for the selected aggregates to evaluate the effects of organic amendments as a non-structural best management practice. The results illustrated that plots having the highest application of biochar and pig slurry showed the lowest colloid dispersibility (i.e. the highest aggregate stability). In the same plot based on CT scanning on aggregates, the increase in the organic carbon content led to an increase in the macroporosity. This increase in macroporosity corresponds to a lower measured tensile strength and specific rupture energy due to the crumbling of the soil aggregates. Our preliminary results therefore indicate that biochar and slurry application after two years are able to reduce the runoff potential of the soil leading to an improvement of the aggregate stability thereby minimizing the erosion potential of the soil.

Keywords: aggregate stability, X-ray computed tomography, biochar, tensile strength, soil erosion

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[1] PhD student of Aarhus University, Department of Agroecology, Ataalah.khademalrasoul@agrsci.dk