Tillage-induced short-term soil organic matter turnover and respiration

Abstract

Abstract. Tillage induces decomposition and mineralisation of soil organic matter (SOM) by the disruption of macroaggregates and may increase soil CO 2 efflux by respiration, but these processes are not well understood at the molecular level. We sampled three treatments (mineral fertiliser: MF; biogas digestate: BD; unfertilised control: CL) of a Stagnic Luvisol a few hours before and directly after tillage as well as 4 days later from a harvested maize field in northern Germany and investigated these samples by means of pyrolysis-field ionisation mass spectrometry (Py-FIMS) and hot-water extraction. Before tillage, the Py-FIMS mass spectra revealed differences in relative ion intensities of MF and CL compared to BD most likely attributable to the cattle manure used for the biogas feedstock and to relative enrichments during anaerobic fermentation. After tillage, the CO 2 effluxes were increased in all treatments, but this increase was less pronounced in BD. We explain this by restricted availability of readily biodegradable carbon compounds and possibly an inhibitory effect of sterols from digestates. Significant changes in SOM composition were observed following tillage. In particular, lignin decomposition and increased proportions of N-containing compounds were detected in BD. In MF, lipid proportions increased at the expense of ammonia, ammonium, carbohydrates and peptides, indicating enhanced microbial activity. SOM composition in CL was unaffected by tillage. Our analyses provide strong evidence for significant short-term SOM changes due to tillage in fertilised soils.

The Effects of Crops Together with Winter Cover Crops on the Content of Soil Water-Stable Aggregates in Organic Farming

“…Among crops, potato, due to its high tillage requirements, is known to reduce the WSA content [12,13] as a consequence of enhanced mineralization of the soil organic matter [14] as well as by the mechanical disruption of aggregates. The effects of legumes on the WSA content are not unambiguously understood.…”

How to best address spatial and temporal variability of soil‐derived nitrous oxide and methane emissions

“…Differences between 2P‐ and MP‐ approaches should be most pronounced for high flux rates. Therefore, we selected two sites that revealed high emissions from the available data for testing the “sample allocation effect” on annual balances, one rewetted fen for high CH 4 ( Günther et al, ) and one fertilized cropland for high N 2 O emission rates ( Fiedler et al, , ). Both sites featured 18 measurement locations (CH 4 : six replicates in each of three dominant plant stands; N 2 O: three spatial replicates in each of six agricultural treatments).…”

“…We base our tests on data of more than 3900 flux measurements that were performed in several ecosystem types between 2010 and 2014 (see Tab. A1 in Appendix, available at: https://github.com/niebert/JungkunstOpinion2018/archive/master.zip) and are described in detail elsewhere ( Huth et al, ; Günther et al., , ; Fiedler et al, , ; Tiemeyer et al, ). Furthermore, we performed model runs to detect highly probable hot moments during which measurements should be increased.…”

Contribution Analysis Of Permanent And Sporadic Controls Of Co2 Efflux From Chernozems Over Four Seasons

“…are also involved. A known pulse component of soil CO 2 emission is the release of carbon dioxide during mechanical tillage (ploughing, harrowing), harvesting, the passage of machinery over the fields, and any sufficientl mechanical load (Markovskaya et al 2014;Cherkassov et al 2013;Stupakov 2014;Akbolat et al 2009;Bojarszczuk et al 2017;Fiedler et al 2016).…”