Distribution of organic carbon in the stable soil humic fractions as affected by tillage management

Abstract

Murage, E. W. and Voroney, P. 2008. Distribution of organic carbon in the stable soil humic fractions as affected by tillage management. Can. J. Soil Sci. 88: 99Á106. Soil humus comprises a large and stable pool of soil organic matter (SOM); hence a better understanding of the fate of C in soil humic fractions can provide valuable information for the development of alternative tillage practices that will lead to long-term soil C sequestration. We used d 13 C techniques to investigate the effects of tillage on the dynamics of native (C 3 ÃC) and corn derived C (C 4 ÃC) in fulvic acid (FA), humic acid (HA) and humin fractions. Humic substances were extracted from soils cropped to corn for 11 yr and managed under either conventional (CT) or no-tillage (NT), and from a conventionally tilled soil under 55 yr of tobacco/rye rotation. Notillage resulted in higher proportions of C 4 ÃC in the upper 5 cm and generally lower C 4 ÃC proportions below 5 cm than CT. Up to 31, 27 and 34% of C 4 ÃC were assimilated into FA, HA and humin fractions, respectively, indicating that even the humin fraction, often described as passive, old or resistant, acted as a sink of recently added C, and that it is heterogeneous with some of its components being young. Recovery of large proportions of C 3 ÃC in the humic fractions demonstrated their importance in the long-term stabilization of SOM. Within each sampling depth, there were no unique differences in the distribution of C 3 ÃC among the three humic fractions, suggesting similar turnover of C 3 ÃC in all the fractions. Therefore, there was no unique active fraction corresponding with the concept of C pools with defined turnover characteristics used in models of SOM turnover.Key words: Soil humic fractions, corn derived C, native C, d13 C techniques, tillage practicesMurage, E. W. et Voroney, P. 2008. Incidence du travail du sol sur la re´partition du carbone organique dans les fractions humiques stables. Can. J. Soil Sci. 88: 99Á106. L'humus du sol constitue un important et stable re´servoir de matie`re organique. C'est pourquoi mieux comprendre le sort du carbone dans les fractions humiques nous procurerait des renseignements pre´cieux pour e´laborer de nouvelles pratiques de travail du sol susceptibles de favoriser une se´questration al ong terme du carbone. Les auteurs se sont servis des techniques au d 13 C pour e´tudier les conse´quences du travail du sol sur la dynamique du carbone naturel (C ÃC 3 ) et du carbone issu du maı¨s (CÃC 4 ) dans l'acide fulvique (AF), l'acide humique (AH) et l'humine. Les substances humiques ont e´te´extraites d'un sol sur lequel on avait cultive´du maı¨s pendant 11 ans avec travail classique (TC) et non-travail du sol (NT), ainsi que d'un sol travaille´de la manie`re usuelle sur lequel du tabac et du seigle avaient e´te´cultive´s en rotation pendant plus de 55 ans. Le non-travail du sol engendre une plus forte proportion de C ÃC 4 que le TC a`une profondeur supe´rieure a`5 cm. Jusqu'a`31, 27 et 34 % du CÃC 4 se transforme respectivement en AF, AH et...

Effect of soil type and management (organic vs. conventional) on soil organic matter quality in olive groves in a semi-arid environment in Sierra Mágina Natural Park (S Spain)

“…This stabilization, along with the incorporation of more plant residues, could help increase the soil organic C stock, and moreover, contributing agro-environmental benefits, such as increased soil fertility, erosion prevention, etc. These results coincide with those of other authors concerning the positive effect of no-tillage management on the increase in stable soil humic fractions content (Murage and Voroney, 2008), and on the contrary, its decrease under continuous tillage despite their intrinsic chemical recalcitrance (Bongiovanni and Lobartini, 2006).…”

Tillage impacts on the fractions and compositions of soil organic carbon

“…Different SOC fractions transformed each other, part of active SOC emissions of CO 2 , and part of it transformed into the steady-state SOC. A similar study of Murage and Voroney (2008) reported that PT was favoring to decompose crop residues into structural organic carbon (slow SOC). Therefore, it was the reason why slow SOC in PT is greater than NT and DL.…”

Challenging Balance between Productivity and Environmental Quality: Tillage Impacts

“…Murage and Voroney (2008) reported tillage eff ects on the dynamics of native C (C3-C) and corn-derived C (C4-C) in fulvic acid (FA), humic acid (HA), and humin fractions:…”