Biochemical composition and mineralization kinetics of organic inputs in a sandy soil

• Published in: Soil biology & biochemistry 2002-02, Vol.34 (2), p.239-250
• Main Authors: Thuriès, L, Pansu, M, Larré-Larrouy, M-C, Feller, C
• Format: Article
• Language: English
• Subjects: Added organic material; Biochemical analysis; Composts; Mineralization kinetics; Modeling; Organic carbon; Organic fertilizers; Sandy soil
• ISSN: 0038-0717; 1879-3428
• DOI: 10.1016/S0038-0717(01)00178-X

The carbon mineralization of added organic materials (AOM) in soil was assessed by combining laboratory and modeling approaches. The AOM used in the organic fertilizer industry included: plant residues from agri-food origin, animal wastes, manures, composts, and organic fertilizers. They were fractionated by sequential analyses of fibers and analyzed for C, N and ash contents. A previous kinetic study permitted to select two predictive models for AOM C mineralization in a sandy soil. These models, m4 and m6, were respectively defined by (i) two compartments (labile L and very resistant R) with three parameters: P L (proportion of L), and k mL , k mR (kinetic constants of L and R); (ii) three compartments (very labile L′, resistant R′ and stable S), with two parameters: P′ L and P S (proportions of L′ and S) with fixed kinetic constants at 28 °C, 75% WHC. We tested for the best prediction of the above parameters with the analytical data. These predictions were significant for the whole AOM set, but to a lesser degree for the C mineralization of AOM with contrasted characteristics. A Principal Component Analysis (PCA) was used to classify the AOM according to their biochemical contents into two groups: (+) ligneous ones with relatively high C and low N contents (mostly plant-originated AOM), and (−) more nitrogenous ones, poorer in organic C and ligno–cellulosic fibers (mostly animal-originated or partially composted AOM). The classification improved the predictive equations, which use one to three biochemical variables in agreement with the conceptual definition of the parameters. P′ L, P L and P S were more accurately estimated than k mL and k mR . For most of the AOM, m6 gave better simulations than m4. From m6 equations, the conceptual compartments L′, R′ (with P′ R=1− P′ L− P S) and S appeared to correspond to (i) parts of soluble, nitrogenous and hemicellulosic compounds, (ii) cellulose and the remaining fraction of hemicelluloses, (iii) the ligneous fraction, respectively.