Tillage impacts on the fractions and compositions of soil organic carbon

Abstract

This study aimed to reveal the impacts of tillage systems on the fractions (active, slow, and passive carbon) and chemical compositions of soil organic carbon (SOC). A long-term (26 years) tillage experiment in northeast China examined no-tillage (NT), plowing tillage (PT) and deep loosing (DL). The soil samples (from a depth of 0-20 cm) were wet-sieved into five aggregate classes (1000-2000 μm, 500-1000 μm, 250-500 μm, 50-250 μm, and b50 μm). The active carbon (C) and passive C were detected in the 500-1000 μm, 250-500 μm, and 50-250 μm aggregates, and the chemical compositions of SOC in micro-aggregates (b 250 μm) and macro-aggregates (>250 μm) were assessed by CPMAS 13 C NMR. Macro-aggregates contained more SOC concentration than micro-aggregates. However, PT resulted in a greater SOC concentration in 50-500 μm aggregates. NT and DL increased the active C and decreased the slow C in 500-1000 μm aggregates, whereas PT showed the inverse. The 13 C NMR spectrum demonstrated that NT increased alkyl-C content, PT obtained a higher carbonyl-C concentration, and DL gained a greater O-alkyl-C concentration. Moreover, evaluating the impacts of tillage systems on the complexity revealed that the most complicated structure was presented in NT, the least in PT, whereas DL had an intermediate effect. Active C contains C2-C6 carbohydrate and anomeric C (C1) polysaccharides, slow C consists of aldehyde-C, ketonic-C and quinone-C, and the passive C is enriched in aromatic-C. In conclusion, long-term tillage systems significantly affected the fractions and compositions of SOC, with NT stabilizing the SOC.

Effects of Experimental Warming and CO2 Concentration Doubling on 13C CPMAS NMR Spectra of Humin in Coniferous Forest Ecosystems of the Eastern Tibetan Plateau in China

“…The relatively high O-alkyl-C content and the relatively low aromatic-C content indicated the poor humification degree of humin in this kind of soil ecosystem. The chemical structure characteristics of humin were similar to those observed in other reports [37]. However, the peaks of the specific compounds detected in our experiment were different from those of Zhang et al [26], who identified larger intensity and more dominant peaks in the alkyl C region of humin and a lower O-alkyl C region in a typical Hapludoll substrate of northeast China as compared with this study.…”

“…In the alkyl C region, the dominant peak at 30 ppm represented the resonance of the amorphous -(CH 2 )n-, and the resonance at 33 ppm was attributed to crystalline -(CH 2 ) n - [38]. In the O-alkyl C region, four peaks (at 55, 62, 73, and 104 ppm) were attributed to methoxyl C, carbinol alcohol-C structure, the -CH(OH)-in carbohydrate, and double oxygen-C in polysaccharide, respectively [37,39]. In the region for aromatic C, the signal of aryl C, appearing at 129 ppm, could be mainly attributed to the aromatic C substituted by -COOH or -COOMe and the unsubstituted aromatic meta carbons bearing an oxygen or nitrogen atom [40].…”

Beneficial effects of reduced tillage and green manure on soil aggregation and stabilization of organic carbon in a Mediterranean agroecosystem

“…Our results also show the positive effect of the incorporation of plant residues by tillage (rather than leaving them on the soil surface), which could result in better contact between soil particles and soil microbes -hence improving the physical-chemical protection of OC (Christopher et al, 2009Zhao et al, 2012. In fact, we found a strong, positive correlation between the percentage of small macroaggregates and the C concentration of the free light fraction (an indicator of plant material inputs) in treatment RTG (r = 0.76, p < 0.01) and a marginal correlation in RT (r = 0.40, p < 0.10), while no correlations were found in NT.…”

Change of Soil Carbon Fractions and Water-Stable Aggregates in a Forest Ecosystem Succession in South China

“…Recently, many studies have investigated the effects of land-use change on SOC and water-stable aggregates [11][12][13][14][15]. However, very little research concentrated on forests.…”