Unraveling Carbon and Nitrogen Dynamics in Cattle Manure: New Insights from Litterbag Incubation

https://doi.org/10.3390/nitrogen6030056

https://www.mdpi.com/2504-3129/6/3/56

Abstract: 

Management of livestock manure is a major concern due to its environmental impacts; consequently, laboratory-based incubations aim to quantify the C and N mineralization of organic matter (OM) to assess its potential to supply OM to soils. However, they can be limited by methodological constraints, notably the drying process of organic products. While litterbag experiments allow in situ decomposition of OM to be monitored, they often focus only on mass loss on a dry matter basis, which may overestimate biodegradation rates. To address these limitations, we designed an experiment that combined the measurement of material fluxes with the characterization of OM using transmission electron microscopy. Raw and dried farmyard cattle manure were incorporated into the soil and incubated in litterbags (200 µm mesh) for 301 days. The results demonstrated that drying significantly altered the biochemical composition of the cattle manure and influenced its microbial dynamics at the beginning of the incubation. However, this alteration did not influence the C mineralization rate at the end of incubation. Biodegradation alone could not explain C losses from litterbags after day 112 of incubation, which supports the assertion that physical and biological processes transferred large amounts of matter from the litterbags to the soil. These results highlight the importance of conditioning samples before laboratory incubations.

Keywords: carbon loss; nitrogen dynamics; mineralization; controlled conditions; transmission electron microscopy; drying impact; microbial activity