Tillage Practices Of A Clay Loam Soil Affect Soil Aggregation And Associated C And P Concentrations

article i nfo Under long-term cultivation, greater accumulations of soil organic matter (SOM) and phosphorus (P) are found in the surface soil layer under no-till (NT) versus mouldboard ploughing (MP) practices. Our objective was to evaluate the effects of NT and MP practices on concomitant SOM and P distribution and sorption characteristics among water-stable aggregates and non-aggregated particles. The study was conducted in Quebec, Canada, as part of a long-term corn and soybean rotation experiment (established since 1992) on a clay loam soil of the St-Blaise series (Dark Grey Gleysol). Soil samples were collected in the fall of 2007 in the 0-5 cm layer from plots under NT and MP receiving 35 kg P ha -1 and 160 kg N ha -1 . Samples were separated into three water-stable aggregate-sized classes (macro, 2000-250 μm; meso, 250-180 μm; micro, 180- 53 μm) and (silt+clay)-sized particles (b53 μm) using wet-sieving. Macro aggregates made up 60.2 and 48.5% of total soil weight under NT and MP, respectively. In wet-sieved soils from NT plots, water-extractable P (Pw) concentration increased in the order (silt+clay)-sized particlesbmicro-bmeso-bmacro-aggregates; under MP, micro-, meso-, and macro-aggregate fractions had the same Pw concentration, while the (silt+clay)- sized particles showed the lowest Pw concentration. The hierarchy observed among aggregate-sized classes