A theoretical approach to soil porosity and sealing development using simulated rainstorms

Macroporosity, pore shape and size distribution were analysed in samples collected during a field rain simulation campaign. Soils were a Typic Eutrochrept and a Typic Udorthent, eroded phase, under different crops and treatments (1 lucerne, 1 potato and 2 bare plots). In each plot, 2 rainfall simulations were made and soil samples for thin section analysis were collected. Soil macroporosity decreased most strongly in the bare soil, then in the potato plot and least in the lucerne plot. The porosity reduction was mainly due to a decrease in size of elongated pores. The decrease of porosity was associated with an increase in runoff rate. The data on elongated pore dynamics were compared with equations based on a physical interpretation of the processes leading to sealing (mainly, porosity reduction due to sedimentation and impacting drops). The equations were compared successfully with the experimental trends. They can be considered as a first mathematical layout, which may be developed into a physically based algorithm.B.V.