title: Combination of a crop model and a geochemical model as a new approach to evaluate the sustainability of an intensive agriculture system.
abstract: By combining a crop model (STICS) and a geochemical model (PHREEQC), a new approach to assess the sustainability of agrosystems is proposed. It is based upon aqueous geochemistry and the stepwise modifications of soil solution during its transfer from the surface till aquifer. Meadows of Crau (SE France), irrigated since the 16th century, were field monitored (2012-2015) and modelled. Except for N, the mineral requirements of hay are largely covered by dissolved elements brought by irrigation water with only slight deficits in K and P, which are compensated by P-K fertilizers and the winter pasture by sheep. N cycle results in a very small nitrate leakage. The main determinants of the chemical composition changes of water are: concentration by evaporation, equilibration with soil pCO2, mineral nutrition of plants, input of fertilizers, sheep grazing, mineral-solution interactions in superficial formations till the aquifer, including ion exchange. Inverse modelling with PHREEQC allows for quantifying these processes. For groundwater, measured composition fit statistically very well with those computed, validating thus this approach. This long-term established agrosystem protects both soil and water resources: soil nutritional status remains constant with even some P and (minor) K fixation in soils; long-term decarbonatation occurs but it is greatly slowed by saturation of irrigation water by carbonate; P fixation in soil protects groundwater from eutrophication.
authors.affiliation: UAPV - INRA - UMR 1114 Emmah, Université d'Avignon, Domaine Saint-Paul, Site Agroparc, Avignon 84914, France. Electronic address: gihan.mohammed@inra.fr.
authors.forename: Gihan
authors.initials: G
authors.lastname: Mohammed
authors.affiliation: UAPV - INRA - UMR 1114 Emmah, Université d'Avignon, Domaine Saint-Paul, Site Agroparc, Avignon 84914, France. Electronic address: fabienne.trolard@inra.fr.
authors.forename: Fabienne
authors.initials: F
authors.lastname: Trolard
authors.affiliation: UAPV - INRA - UMR 1114 Emmah, Université d'Avignon, Domaine Saint-Paul, Site Agroparc, Avignon 84914, France. Electronic address: marina.gillon@univ-avignon.fr.
authors.forename: Marina
authors.initials: M
authors.lastname: Gillon
authors.affiliation: UAPV - INRA - UMR 1114 Emmah, Université d'Avignon, Domaine Saint-Paul, Site Agroparc, Avignon 84914, France. Electronic address: anne-laure.cognard-plancq@univ-avignon.fr.
authors.forename: Anne-Laure
authors.initials: AL
authors.lastname: Cognard-Plancq
authors.affiliation: UAPV - INRA - UMR 1114 Emmah, Université d'Avignon, Domaine Saint-Paul, Site Agroparc, Avignon 84914, France. Electronic address: andre.chanzy@inra.fr.
authors.forename: André
authors.initials: A
authors.lastname: Chanzy
authors.affiliation: UAPV - INRA - UMR 1114 Emmah, Université d'Avignon, Domaine Saint-Paul, Site Agroparc, Avignon 84914, France. Electronic address: guilhem.bourrie@inra.fr.
authors.forename: Guilhem
authors.initials: G
authors.lastname: Bourrié
keywords: Biogeochemical modelling; Irrigation; Meadow; Mineral flux; Water quality