Wednesday, November 15, 2006
283-15
No Extra Soil C storage in No-Till Systems : a Meta-Analysis.
Inigo Virto1, Claire Chenu1, and May Balabane2. (1) INAPG UMR Bioemco, Batiment Eger, Grignon, 78850, France, (2) INRA Unité Pessac, route de St Cyr, Versailles, France
Although most conversions from conventional (CT) to no-tillage (NT) are associated with an extra storage of C in soil (SOC), several studies report the absence of any supplemental SOC. So far, no scientific work has been published with the aim of developing hypothesis to explain such scenarios at a global scale. We understand that these "abnormal" situations are very informative for understanding C dynamics in soils. Their study can inform us about (i) the mechanisms controlling soil C sequestration and (ii) the factors that regulate such mechanisms. We developed a set of hypotheses considering the possible mechanisms leading to a lack of soil extra C sequestration under NT. They contemplate the major pathways for organic C to enter and leave the soil. Also we identified the major biophysical (climate, soil, topography) and agronomical (fertilization, rotation, time, etc) factors most likely related to such processes.
We performed a compilation of international data on the topic, selecting the situations reporting at least one situation of no extra C stock under NT, and including C sequestration data in an equivalent soil mass under NT and CT, or supplying data allowing for its quantification. We also collected available data of biophysical (climate, soil, land) and agronomical (rotation intensity, fertilization, timing) factors in the selected situations. We used these data to test our hypotheses and to study the relationship between the selected factors and soil C variability and stock in the selected situations. Equal crop aerial biomass in CT and NT was repeatedly observed in relation to no extra soil C stock under NT. Limiting climatic factors and/or some agricultural practices, especially fertilization and the rotation type (i.e. the kind of crops included in it) and intensity (time of soil under crops), seem to have on the processes impeding extra soil C stick under NT.
We performed a compilation of international data on the topic, selecting the situations reporting at least one situation of no extra C stock under NT, and including C sequestration data in an equivalent soil mass under NT and CT, or supplying data allowing for its quantification. We also collected available data of biophysical (climate, soil, land) and agronomical (rotation intensity, fertilization, timing) factors in the selected situations. We used these data to test our hypotheses and to study the relationship between the selected factors and soil C variability and stock in the selected situations. Equal crop aerial biomass in CT and NT was repeatedly observed in relation to no extra soil C stock under NT. Limiting climatic factors and/or some agricultural practices, especially fertilization and the rotation type (i.e. the kind of crops included in it) and intensity (time of soil under crops), seem to have on the processes impeding extra soil C stick under NT.