Surface seal formation which is common in cultivated soils of semi arid and arid regions significantly

affects infiltration and soil erosion and creates serious problems for crop production. Soil samples (18

samples) were selected from Guilan, Qhazvin and Zanjan provinces. The soil samples were analyzed for

electrical conductivity, pH, organic matter, cation exchange capacity, primary and secondary particle size

distribution, mean weight diameter and geometric mean diameter, fractal dimension of aggregates, and

bulk density. For estimating erosion rate and runoff, soil samples packed in a 30×35 cm drainable

detachment tray and subjected to simulated rainfall for 30 minutes. Runoff rate and sediment

concentration were measured during the experiment. An undisturbed surface sample was collected to

identify seal formation by thin section analysis using image tools software. Collected data were examined

by multiple regression analysis to determine the relations between aggregate stability, seal formation,

runoff and soil erosion and soil properties. There was a significant relationship between aggregate

stability indices and surface sealing formation which controls runoff and erosion rate. Results indicated

that runoff rate and soil erosion are related to soil texture, organic matter, sodium exchange percentage

and aggregate stability.