A THEORETICAL APPROACH TO SOIL POROSITY AND SEALING DEVELOPMENT USINGSIMULATED RAINSTORMS

Macroporosity, pore shape and size distribution were analysed in sampl es collected during a field rain simulation campaign. Soils were a Typ ic Eutrochrept and a Typic Udorthent, eroded phase, under different cr ops and treatments (1 lucerne, 1 potato and 2 bare plots). In each plo t, 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 elonga ted pores. The decrease of porosity was associated with an increase in runoff rate. The data on elongated pore dynamics were compared with e quations based on a physical interpretation of the processes leading t o sealing (mainly, porosity reduction due to sedimentation and impacti ng drops). The equations were compared successfully with the experimen tal trends. They can be considered as a first mathematical layout, whi ch may be developed into a physically based algorithm. (C) 1997 Elsevi er Science B.V.