Soil Crusting

Crusting develops as raindrop impact detaches fine particles from weakly bound surface aggregates; these particles then clog surface pores and, on drying, bind into a thin, dense layer that can be substantially harder than the soil immediately beneath it.

• Structural crusts form from aggregate breakdown and particle redistribution by raindrop impact
• Depositional crusts can also form where sediment-laden runoff settles and dries on the surface

A hardened surface crust can physically impede small-seeded crops from emerging, particularly if it forms after planting but before seedlings break through, contributing to poor or uneven stands. Crusting also reduces water infiltration, increasing runoff and, in turn, erosion risk on sloping land.

Crusting is generally identified through field observation: a visibly hardened, often cracked surface layer, poor or delayed seedling emergence following a rainfall event after planting, and visible ponding or increased runoff during subsequent rain.

Prevention generally focuses on protecting the surface from direct raindrop impact and building aggregate stability, so that even where rain is intense, the surface resists breakdown and sealing.

• Maintain crop residue or cover crops to intercept raindrop energy before it reaches bare soil
• Build soil organic matter to improve aggregate stability over time
• Apply gypsum on sodic-prone soils where elevated exchangeable sodium contributes to crusting
• Adjust planting depth and timing to reduce the chance of a crust forming over emerging seedlings