Modelling soil carbon dynamics with various cropping sequences on the rolling pampas

Abstract

The two-compartment model of Hénin-Dupuis (1945) was tested to track the medium-term (13 years) evolution of C reserves in the silty soils of the rolling pampas in Argentina for various crop rotations. The coefficient of annual mineralisation, theoretically constant in the model, depends in fact on the amount of organic residues returned. The model is thus open to question. A simple model with three carbon fractions (harvest residues, active fraction and stable fraction) is proposed. It enables the changes in the soil organic reserves to be well simulated. However, a simple statistical fit of the three parameters of the model gives an infinite number of solutions. Use of the 13 C natural abundance method allows evolution of the young and old soil carbon fractions to be separated and tracked, and to determine the three parameters unambiguously. The results show that the stable fraction represents most of the initial soil organic C reserve: 60-68 %. The humification parameter increases in proportion to the lignin concentration of the crop residues. Intensification of soil tillage accelerates the mineralisation of the soil organic matter. (© Inra/Elsevier, Paris.) soil carbon / model / 13 C abundance / rolling pampas / cropping Résumé-Modélisation des l'évolution des stocks de carbone des sols de la Pampa argentine pour différentes rotations culturales. Le modèle bicompartimental de Hénin-Dupuis (1945) a été évalué pour suivre l'évolution à moyen terme (13 ans) des stocks de C dans des sols limoneux de la Pampa ondulée en Argentine, pour diverses rotations de culture. Le coefficient de minéralisation annuel, théoriquement constant dans le modèle, dépend en fait du niveau des restitutions organiques. Le modèle est donc ainsi remis en cause. Un modèle simple à trois compartiments carbonés (résidus de récolte, fraction active et fraction stable) est proposé. Il permet de bien simuler l'évolution des stocks organiques du sol. Cependant, un simple ajustement statistique des trois paramètres du modèle donne une infinité de solutions. L'utilisation de la méthode d'abondance naturelle en 13 C permet de séparer et de suivre les évolutions de carbone jeune et du carbone ancien du sol, et de pouvoir déterminer les trois paramètres de façon univoque. Les résultats obtenus indiquent que la fraction stable représenterait la plus grande partie du stock de C organique initial: 60 à 68 %. Le rendement d'humification augmente proportionnellement à la concentration en lignine des résidus de récolte. L'intensification du travail du sol induit une accélération de la minéralisation de la matière organique du sol. (© Inra/Elsevier, Paris.

Changes in soil organic matter under different land management in misiones province (Argentina)

“…In our study, the contribution of elephant grass material to the total C stock was smaller (20% at 0 -0.15 m; Table 2), probably due to a lower annual C input and/or to a microbial population of the degraded soil (yerba mate) not adapted to efficiently process the SOM. Figure 2 shows the evolution of C DP and C DF calculated by 13 C data and predicted using Andriulo et al (1999) model. The same exponential kinetics, which take into account the hypothesis of a stable fraction of SOM, have been used in other SOM turnover studies (Jenkinson & Rayner, 1977;Parton et al, 1987;Balesdent et al, 1988).…”

“…four years. The coefficient of mineralization (k) of our model (0.28 year -1 ) may be compared with the annual rate of SOC loss (k 2 ) using equation 13 (Andriulo et al, 1999):…”

“…To study the dynamics of C under the association of yerba mate and elephant grass, the model proposed by Andriulo et al (1999) was used. In this three-compartment model (Figure 1), SOM is separated into stable and active fractions and the evolution of the C stock is described by the following equation:…”

Factors affecting soil organic matter conservation in Mediterranean hillside winter cereals-legumes cropping systems

“…Of the various indicators and models described in the literature to estimate the SOM balance (Mary and Guerif, 1994;Andriulo et al 1999;Bockstaller and Girardin, 2003;Bayer et al, 2006;Castoldi and Bechini, 2009), the equation developed by Hénin and Dupuis (1945) still forms the basis of all these indicators and models (Bockstaller et al, 2008;Bertora et al, 2009;Bechini et al, 2011;Di Bene et al, 2011). This equation is based on first order kinetics and is useful for estimating how SOM evolves, for testing hypotheses and for field-scale analyses (Huggins et al, 1998).…”

Projection of Soil Organic Carbon Reserves in the Argentine Rolling Pampa Under Different Agronomic Scenarios. Relationship of these Reserves with Some Soil Properties

“…The term "pool" is used to describe the theoretically separated, kinetically delineated component of SOC and the term "fraction" is used to describe measurable organic matter components [20,21]. Models designed to predict SOC dynamics have incorporated at least two contrasting pools: a passive or stable pool and a labile or active pool [22][23][24]. Although the size, number and turnover rates of the pool used in multicomponent models vary, common divisions include compartments with time constants (1/k), where k is the mineralization coefficient measured in years, decades, centuries or millennia from the most active to the most persistent pool [25].…”