The incidence of black scurf of potato is more in

The incidence of black scurf of potato is more in Sandy soil.
Black scurf is caused by the fungus Rhizoctonia solani, which can exist in the soil in the absence of potatoes.
Rhizoctonia solani is a soil pathogen and thus is affected by soil conditions. Black scurf and stem canker are more severe in soils that are cool and moist. It is more common in crops grown in sandy to sandy loam and moderately wet soils.