soilsurface

Soil surface, often written as soilsurface in compact form, refers to the outermost boundary of the soil body where soil meets the atmosphere. It encompasses the uppermost mineral and organic layers that are directly exposed to weather, moisture, temperature fluctuations, and living organisms. The condition of the soil surface influences a range of processes, including water infiltration, evaporation, gas exchange, seedling emergence, and microbial activity.

The surface zone is characterized by features such as roughness, litter or mulch layers, and crusts. Crusts can form physically from particle sealing, chemically through mineral reactions, or biologically via communities of cyanobacteria, lichens, mosses, and other organisms. In arid and semiarid regions, biological soil crusts and physical crusts are common and can strongly affect infiltration and erosion. Surface roughness, created by aggregates and residues, modulates runoff and helps protect against erosion by dissipating raindrop impact and enhancing infiltration.

Several processes act at the soil surface. Evaporation and transpiration draw water away, while rainfall and irrigation drive infiltration and potential runoff. Wind can remove fine particles, especially from bare surfaces. Temperature extremes influence biological activity and crust stability. The surface responds quickly to disturbances such as tillage, grazing, and vegetation removal.

Management practices aiming to protect the soil surface—such as cover crops, residue retention, mulching, and reduced tillage—seek to improve infiltration, reduce erosion, stabilize seedlings, and support soil health. Measurement of surface roughness, crust strength, and infiltration rate are common indicators of surface condition.