Effect of conventional and minimum tillage on physical and biochemical stabilization of soil organic matter

Abstract

The objectives were to investigate (1) to which extent water-stable macro-and microaggregates sequester organic matter (OM) in a minimum tillage (MT) system compared to a conventional tillage (CT) system and (2) if the content of biochemically stabilized OM differs between both tillage systems, and (3) to study the temporal dynamics of the distribution of aggregate size classes and of storage of OM within aggregates in the field. Surface soils (0-5 cm) and subsoils (10-20 cm) were sampled after fallow (March 2007) and directly after tillage (November 2007) from a long-term experimental field near Göttingen, Germany. Macroaggregates (>0.25 mm) were in general less abundant after fallow than directly after tillage. In March, only 21% (CT) and 45% (MT) of C org was stored within macroaggregates in the surface soil, whereas in November, the percentages increased to 58% and 73%, respectively. CT and MT soils of both depths were incubated as bulk soil (CT bulk , MT bulk ) and with macroaggregates disrupted (<0.25 mm) (CT md , MT md ) for 28 days at 22°C and water content of 50% of the maximum water holding capacity. For the MT bulk and MT md surface soils, C mineralization was significantly higher compared to the CT soils. Incubation of md soils did not generally result in a significantly higher C mineralization compared to the respective bulk soils, except for the MT md subsoil. Acid hydrolysis showed that the proportion of biochemically stabilized, nonhydrolysable, C org to total C org was lower in the MT than in the CT soils. Overall, the data indicate that the effect of physical stabilization of OM stored in the macroaggregates may not be a mechanism protecting very labile C with a turnover time of weeks, but that longer preservation likely occurs after macroaggregate transformation into microaggregates, and the surplus of OM found in the surface soil of MT does not only depend on the biochemically stabilized OM. Finally, our data suggest that the temporal variability of distribution of aggregate size classes in the field is large, but spatial and operator variability also contributed to the observed differences.

Stability of Soil Organic Matter and Soil Loss Dynamics under Short-term Soil Moisture Change Regimes

“…This may have been caused by the aging of the V. karroo leaves, which were harvested at the beginning of winter period (May). However, the results agreed with [13], who observed that C/N ratio had no influence on different forest litter material and suggested other factors such as lignin/N ratio or secondary metabolites like polyphenols to influence decomposability of litter.…”

“…Several studies have indicated that the chemical and biochemical quality of litter affects mass loss during decomposition [10,11]. The addition of higher quality substrate (lower C/N ratio of <24 and lower lignin content) resulted to increased SOC mineralization compared to the addition of lower quality (C/N ratio >24) substrate [12][13][14]. Since the soil microbes need N (and other essential elements) as well as C, if there is little N in the residue, decomposition is slow.…”

“…The C/N ratio in plant residues is highly variable and increases with maturity. An ideal substrate material was found to have C/N ratio=24 to satisfy the N requirement of microbes [12,13]. If the C/N ratio of residue >24, available soil N is consumed by microbes and this retards decomposition rate.…”

Effects of permanent grass versus tillage on aggregation and organic matter dynamics in a poorly developed vineyard soil

“…Munoz-18 Rojas et al 2012;De Moraes Sá et al 2013;Gelaw et al 2013;Parras-Alcántara et al 2013, 201419 Srinivasarao et al 2014;Yu and Jia 2014;Behera et al 2015;Peng 2015). Agriculture can strongly 20 limit SOM accumulation, influencing soil aggregate formation and turnover (Jastrow 1996;Cerdà, 21 2000;Jacobs et al 2010;Gosling et al 2013). In particular, tillage can increase the turnover of 22 macroaggregates (Six et al 2000), consequently limiting the physical protection of SOM, hence the 23 formation of microaggregates inside macroaggregates.…”

The Effect of Tillage on Organic Carbon Stabilization in Microaggregates in Different Climatic Zones of European Russia

“…The stabilization of organic matter (OM) in soil (protection of OM against microbial decomposition) can mainly be attributed to three general mechanisms: spatial inaccessibility, biochemical recalcitrance and organo-mineral association [7]. The importance of these mechanisms can differ for each soil horizon and depends on several factors, such as soil type and texture, mineralogical composition and land use [11].…”