2016 Volume 87 Issue 6 Pages 413-421
We investigated the effects of applying methane-fermentation-digested slurry, derived mostly from dairy cattle waste, on the formation of soil aggregates in grassland. The carbon content of the surface soil (0–5 cm) increased more in the NPK+ digested slurry plot than in the NPK-only plot, indicating the contribution of digested slurry to the storage of carbon in the soil. This greater increase was seen only in the surface soil, and took at least 5 years of application to become significant. In the 7th year of application, the increase in the formation of macro-aggregates (>1000 µm) and grass root weight in the surface soil was greater in the NPK+ digested slurry plot than in the NPK plot. We assume that the grass roots bind micro-aggregates (<250 µm) in the soil. The macro-aggregates of the NPK+ digested slurry plot showed a particularly high accumulation of carbon in particulate organic matter (>53 µm). Both easily decomposable organic matter and recalcitrant organic matter accumulated in macro-aggregates in the NPK+ digested slurry plot. We assume that dead grass roots contributed to the retention of macro-aggregates. The formation of macro-aggregates had no significant effect on the physical properties of the surface soil.
