『Abstract
　An experimental study was carried out in order to evaluate the impact of nitrogen fertiliser-induced acidification in carbonated soils. Undisturbed soil columns containing different carbonate content were sampled in the field. Fertiliser spreading was simulated by NH4Cl addition on top of soil column. Soil solution composition (mainly nitrate and base cations) was studied at the soil column's base. Nitrification occurred to a different extent depending on soil type. Higher nitrification rates were observed in calcareous soils. In all the soil types, strong correlations between leached base cation and nitrate concentrations were observed. Regression coefficients between base cations, nitrate and chloride were used to determine the dominant processes occurring following NH4Cl spreading. In non-carbonated soils, nitrogen nitrification induced base cation leaching and soil acidification. In carbonated soils, no change of soil pH was observed. However, fertilisers induced a huge cation leaching. Carbonate mineral weathering led to the release of base cations, which replenished the soil exchangeable complex. Carbonated mineral weathering buffered acidification. Since direct weathering might have occurred without atmospheric CO2 consumption, the use of nitrogen fertiliser on carbonated soil induces a change in the cation and carbon budgets. When the results of these experiments are extrapolated on a global scale to the surface of fertilised areas lying on carbonate, carbonated reactions with N fertilisers would imply an additional flux of 5.7×10¹² mol yr^-1 of Ca + Mg. The modifications of weathering reactions in cultivated catchments and the ability of nitrogen fertilisers to significantly modify the CO2 budget should be included in carbon global cycle assessment.』

1. Introduction
2. Materials and methods
　2.1. Soils and area description
　2.2. Sampling of soil columns
　2.3. Experimental design
　　2.3.1. Soil column treatments and leaching experiments
　　　2.3.1.1. Nitrogen inputs
　　　2.3.1.2. Leaching experiments
　2.4. Analytical methods
　　2.4.1. Solutions
　　2.4.2. Soils
3. Results
　3.1. Soil leachates
　　3.1.1. Elemental concentrations
　　3.1.2. Trends of element fluxes over time
　　　3.1.2.1. Nitrogen leaching
　　　3.1.2.2. Cations leaching
　　3.1.3. Correlations between element fluxes in soil leachates
　3.2. Changes in soil chemistry
　　3.2.1. Soil pH
　　3.2.2. Exchangeable cations pool
4. Discussion
　4.1. Validation of soil column experiments. Comparison of leaching rate estimations with the literature and field results
　4.2. Extent of nitrification in different soils
　4.3. Ammonium transformations in soils and weathering reactions
　4.4. Soil and soil solution modifications as induced by N fertiliser inputs
　4.5. Consequences of nitrogen inputs on soils: implications for cation leaching rates, CO2 budgets and limits of the approach
5. Conclusion
Acknowledgements
References