Soil Crust: Formation, Influence on Soil Productivity, and Management

Soil crusts are formed as a relatively dense layer of non-aggregated soil particles on the surface of cultivated and unvegetated exposed soils. Soil crusts are classified into three morphological types that include physical crusts, chemical crusts, and biological crusts. While physical crusts are the result of modifications of topsoil caused by physical perturbation such as raindrop impacts or sedimentation, chemical crusts are formed by salt encrustation, and biological crusts are formed by soil biological communities such as lichens and algae-binding soil particles. Physical crusts are widespread and include structural crusts and depositional crusts. In relation to agricultural production, the most significant negative impacts of soil crusts are the restrictions on seedling emergence, decreased water infiltration, soil erosion, decreased root functioning, and decreased water utilization by plants. Soil crusting can be avoided by management practices, including rehabilitation, and covering and protecting the soil surface. Providing surface mulching will provide soil protection from the impacts of raindrops leading to the formation of a surface crust. The addition of organic matter sources such as composts and manures is likely to promote stable aggregate formation, thereby preventing crust formation. Soil constraints resulting from crusting can be managed by controlling cultivation practices including surface tilling.