Digital image analysis for the estimation of cracked areas and the soil shrinkage characteristic curve in clay soils amended with composted sewage sludge

Abstract

The formation of cracks in clay soils is a physical process with important agricultural repercussions. The specific case occupying us refers to a dryland olive grove (Olea europaea) grown on a vertisol in the countryside of Córdoba (Spain). For two consecutive years, rates of 20 Mg ha-1 of composted sewage sludge have been applied on this land to attempt to improve the physical and chemical properties of the soil. This study proposes a method for the measurement of cracks in clay soil during a desiccation period in trays. The measurement of the cracked area generated in each treatment (20 Mg ha-1 of compost and control) throughout the time, is done on digital photographs, previously orthorectified. The area of cracks generated after a desiccation process decreased by 7% in clay soils amended with composted sewage sludge. Additionally, the soil shrinkage characteristic curve (SSCC) can be obtained.