Soil surface sealing by liquid dairy manure as analysed by X-ray computed tomography

Abstract The application of animal manure in agricultural production is common around the world. Nevertheless, the effects of surface-applied liquid manures on soil properties are not well investigated. The purpose of this research was to use X-ray computed tomography to assess near-soil surface porosity and to evaluate the thickness of the sealing caused by physical and chemical mechanisms after liquid dairy manure (LDM) application in clayey and sandy clay loam soils. The treatments included application of LDM with 4.3% total solids to determine physical and chemical mechanisms and application of LDM with 0% total solids (filtered) to determine the chemical mechanism of surface sealing. Image analysis obtained by X-ray microtomography was performed before LDM application and 24 h and 7 days after LDM application. Porosity was quantified for each 1-mm layer of the soil. Soil porosity was reduced mainly in the first 5 mm of depth, and this reduction was more distinct in the first 1-mm layer, independent of the soil texture. The decrease in soil porosity in the first mm after application of LDM with 4.3% total solids, at 24 h and 7 days, was around 25 and 6%, respectively, compared with the treatment before LDM application. After application of LDM with 0% total solids, the decrease in soil porosity in the first 1-mm layer at 24 h and 7 days was around 5 and 4%, respectively. Physical pore clogging by solid particles from manure was the main process (around 80%) of soil surface sealing after LDM application.