Response of subsoil organic matter contents and physical properties to long‐term, high‐rate farmyard manure application

Wolff, Maximilian

Kaiser, Klaus

Schumann, Lena
Merbach, Ines
Mikutta, Robert

Schlüter, Steffen

DOI: https://doi.org/10.1111/ejss.13233
Persistent URL: http://resolver.sub.uni-goettingen.de/purl?gldocs-11858/10005
Schumann, Lena; 2 Soil Science and Soil Protection Martin Luther University Halle‐Wittenberg Halle (Saale) Germany
Merbach, Ines; 3 Department of Community Ecology Helmholtz Centre for Environmental Research – UFZ GmbH, Experimental Station Bad Lauchstädt Germany
Mikutta, Robert; 2 Soil Science and Soil Protection Martin Luther University Halle‐Wittenberg Halle (Saale) Germany
Schlüter, Steffen; 1 Department of Soil System Science Helmholtz Centre for Environmental Research – UFZ GmbH Halle (Saale) Germany
Abstract
Application of farmyard manure (FYM) is common practice to improve physical and chemical properties of arable soil and crop yields. However, studies on effects of FYM application mainly focussed on topsoils, whereas subsoils have rarely been addressed so far. We, therefore, investigated the effects of 36‐year FYM application with different rates of annual organic carbon (OC) addition (0, 469, 938 and 1875 g C m−2 a−1) on OC contents of a Chernozem in 0–30 cm (topsoil) and 35–45 cm (subsoil) depth. We also investigated its effects on soil structure and hydraulic properties in subsoil. X‐ray computed tomography was used to analyse the response of the subsoil macropore system (≥19 μm) and the distribution of particulate organic matter (POM) to different FYM applications, which were related to contents in total OC (TOC) and water‐extractable OC (WEOC). We show that FYM‐C application of 469 g C m−2 a−1 caused increases in TOC and WEOC contents only in the topsoil, whereas rates of ≥938 g C m−2 a−1 were necessary for TOC enrichment also in the subsoil. At this depth, the subdivision of TOC into different OC sources shows that most of the increase was due to fresh POM, likely by the stimulation of root growth and bioturbation. The increase in subsoil TOC went along with increases in macroporosity and macropore connectivity. We neither observed increases in plant‐available water capacity nor in unsaturated hydraulic conductivity. In conclusion, only very high application of FYM over long periods can increase OC content of subsoil at our study site, but this increase is largely based on fresh, easily degradable POM and likely accompanied by high C losses when considering the discrepancy between OC addition rate by FYM and TOC response in soil.
Highlights
A new image processing procedure to distinguish fresh and decomposed POM. The increase of subsoil C stock based to a large extend on fresh, labile POM. Potential of arable subsoils for long‐term C storage by large FYM application rates is limited. The increase in TOC has no effect on hydraulic properties of the subsoil.
Subjects
carbon stockcarbon storage
hydraulic properties
particulate organic matter
plant available water content
X‐ray computer tomography
soil structure