Sustainable agriculture as a central science to solve global society issues

Serious global issues such as poverty, illness, food prices, climate changes, global market, pollution, pest adaptation and resistance, soil degradation, decreasing biodiversity and desertification can be explained by the increasing artificialization of human society. Since most issues are now intertwined they cannot be solved anymore by the classical fireman approach. In that respect, the structure of actual science and governmental institutions are probably outdated and should evolve to meet global challenges. Unexpectedly, agronomy appears as a central science to solve current societal issues because agronomists are trained to manage the input of many disciplines such as plant biology, soil science, climate sciences, ecology and chemistry

(13)C/(12)C composition, a novel parameter to study the downward migration of paper sludge in soils†

δ(13)C values of crop and forest soils were measured 8 years after disposal of paper sewage sludge. The carbon transfer from paper sludge downward to the first humic layer is evidenced by a (13)C-enrichnient of up to + 5.6‰ due to the input of (13)C-enriched sludge carbonates. (13)C/(12)C composition is thus a novel, sensitive parameter to follow the downward transfer of paper sludge carbon

Isotopic evidences for microbiologically mediated and direct C input to soil compounds from three different leaf litters during their decomposition

We show the potentiality of coupling together different compound-specific isotopic analyses in a laboratory experiment, where 13C-depleted leaf litter was incubated on a 13C-enriched soil. The aim of our study was to identify the soil compounds where the C derived from three different litter species is retained. Three 13C-depleted leaf litter (Liquidambar styraciflua L., Cercis canadensis L. and Pinus taeda L., δ13CvsPDB ≈ −43‰), differing in their degradability, were incubated on a C4 soil (δ13CvsPDB ≈ −18‰) under laboratory-controlled conditions for 8 months. At harvest, compound-specific isotope analyses were performed on different classes of soil compounds [i.e. phospholipids fatty acids (PLFAs), n-alkanes and soil pyrolysis products]. Linoleic acid (PLFA 18:2ω6,9) was found to be very depleted in 13C (δ13CvsPDB ≈ from −38 to −42‰) compared to all other PLFAs (δ13CvsPDB ≈ from −14 to −35‰). Because of this, fungi were identified as the first among microbes to use the litter as source of C. Among n-alkanes, long-chain (C27–C31) n-alkanes were the only to have a depleted δ13C. This is an indication that not all of the C derived from litter in the soil was transformed by microbes. The depletion in 13C was also found in different classes of pyrolysis products, suggesting that the litter-derived C is incorporated in less or more chemically stable compounds, even only after 8 months decomposition