Degraded arable soils can be helped on their way to restoration and effective carbon sequestration through planting crops with strong root systems, or including deep-rooted plants in rotations.
Research led by Eva Kaštovská at University of South Bohemia in Czechia tested how adding barley shoot and root residues to eroded soils impacted the formation of mineral-associated organic matter (MAOM), which is instrumental in soil carbon storage. The study was an attempt to address “contradictory” results in previous work.
Shoots and roots represented what are considered to be high and low-quality soil inputs, respectively. However, Kaštovská found that slowly-decomposing root carbon accumulated in greater amounts and stabilised more effectively as MAOM in all of the variety of soil types tested in the study. The effect was more pronounced in eroded and fine-textured soils than in those that were not eroded or coarse.
The soils in the study retained between 35 and 75% of the added carbon, with between 10 and 60% of this carbon stabilised in the form of MAOM within the course of the one-year experiment.
A target for carbon farming programmes
“Our results indicate that the intensively managed arable soils with a large carbon saturation deficit, especially those eroded, appear to be strong sinks for stabilised carbon, making them prime targets for carbon sequestration,” Kaštovská wrote in the journal Soil and Tillage Research.
Crop residues were the focus of the work due to the relative ease with which they can be manipulated by farmers, through changing crop rotations and the selection of crop cultivars, she noted.
The way soil organic matter was stabilised, by compounds moving from enriched root matter to mineral surfaces, suggests that farmers could consider the inclusion of robust-rooted crops or plants in rotations as part of plans to improve the quality of degraded soils.
“[This] could help restore or increase stable soil organic matter stocks more rapidly in eroded arable soils” she added.
