Cracking in recent alluvial soils as related to easily determined soil properties

Abstract

Cracking was studied in fifty soils located in two recent alluvial plains and it was related to soil parameters such as clay content, soil moisture content, bulk density and coefficient of linear extensibility (COLE). The total crack area per unit soil surface, the crack width and crack depth were measured by tracing them on transparent sheets. The rate of crack development was also studied in a soil immediately after irrigation. Results showed that crack width increased initially almost linearly with decreasing soil moisture content to a certain level and then increased in a declining rate until a maximum width was attained. Cracks appeared on the soil surface after water was removed from the large soil pores. The total crack area occupied a significant portion of the soil surface reaching a maximum value of 22.7%. Measurements of water flow into the cracks during irrigation were significant and in some soils exceeded the conductivity of the uncracked soil surface. An empirical relation was found, which calculates the total crack area per unit soil surface as a function of clay content, COLE and volumetric moisture content. The average crack width was linearly related to the total crack area measured on the soil surface. Furthermore, the crack depth in the plow layer was logarithmically related to clay content, COLE and moisture content.