Systèmes de culture et statut organique des sols dans le Noyonnais : application du modèle de Hénin-Dupuis

Abstract

On cherche à tester le modèle de HÉ NIN-Du P uis et l'ensemble des références numériques qui lui sont associées à partir d'une enquête sur des parcelles supposées au voisinage de l'équilibre organique et correspondant à une large gamme de sols et de systèmes de culture. Pour cela, on confronte les teneurs d'équilibre calculées à partir des informations sur le sol et le régime d'entretien organique aux teneurs observées. Les deux séries de valeurs ainsi obtenues sont corrélées mais les valeurs calculées sont, en moyenne, inférieures aux valeurs observées surtout si elles sont exprimées en carbone plutôt qu'en matière organique. Différentes hypothèses, susceptibles de rendre compte de ce biais systématique et de la dispersion résiduelle autour de la régression, sont discutées. Vis-à-vis du biais, l'hypothèse la plus plausible est celle d'une surestimation de la minéralisation ; quant à la dispersion, elle est probablement encore liée à celle des statuts organiques antérieurs. En l'état actuel, le modèle de HË N tN-Du p Uts peut être considéré comme un bon instrument de classement des systèmes de culture vis-à-vis de leurs conséquences sur l'évolution de l'état organique du sol dans une région donnée, mais, par rapport à la description d'une évolution, son caractère monocompartimental est sans doute trop simpliste. Mots clés additionnels : Matière organique, résidus de culture, fumier. SUMMARY Cropping system and organic status of soils : application of the 7 V c / ! M-Z) M/ ?MM model. We tested the H EN) N-Du p uis model and the numerical references associated with it. This was done by means of a survey on 89 farm plots, supposed to be close to organic equilibrium and corresponding to a wide range of soils (fig. 1) and cropping systems in a restricted area. For each plot, the expected value of organic content (calculated from information collected on soil and on organic supply) was compared with the observed content. Expected and observed values proved to be correlated (fig. 2 and 3), but expected ones were systematically lower than those observed, especially if the content was expressed as carbon instead of organic matter. Different hypotheses were examined to explain this bias and the residual dispersion around the linear regression (expected content versus observed). It was concluded that the most plausible origins were, for the bias, an overestimation of the annual rate of mineralization k 2 , and, for the residual dispersion, the influence of unknown former organic status. In addition, the collection of numerous results concerning plots where farmyard manure was used allowed us to estimate the isohumic coefficient (k l) of this product (0.34). In the present state of knowledge, the Ht NIN-Du p uis model with associated numerical references can be considered as a good tool for grading cropping systems from the point of view of organic management. However in order to predict the change in organic content of a given soil with time, this tool seems inadequate, due to its monocompartmental character.

Factors Affecting Soil Organic Matter Conservation in Mediterranean Hillside Winter Cereals-Legumes Cropping Systems

“…This suggests that the only relevant input of OM was due to the manure incorporation into the soil, which has been widely observed in the literature (e.g. Boiffin et al, 1986;Accademia Nazionale di Agricoltura, 1991;Castoldi and Bechini, 2006). When we compared combined factors, with or without livestock, we found significant differences in terms of SOM balance both for short-and long-rotations.…”

Roots contribute more to refractory soil organic matter than above-ground crop residues, as revealed by a long-term field experiment

“…For example, Plénet et al (1993) set h for shoots to 0.055 -0.065 and that for roots to 0.16 -0.30. However, the original h for manure given by Hénin and Dupuis (1945) was supported by studies of Delas and Molot (1983) and Boiffin et al (1986). Over the years, the expression and calculation of h has been subject to modifications (e.g., Janssen, 1984).…”

“…Andrén et al, 2008). Using C or soil organic matter analyses and conversions between these can also introduce errors (Boiffin et al, 1986).…”

Net primary productivity and below-ground crop residue inputs for root crops: Potato (Solanum tuberosum L.) and sugar beet (Beta vulgaris L.)

“…Boiffin et al (1986) (1 (data not shown). Assuming a DM content of 20% (only wet weight yields were reported) the average yield was also about 6.5 Mg DM ha…”