Rangeland soil quality--Physical and biological soil crusts (Soil Quality Information Sheet, Rangeland Sheet 7)

TitleRangeland soil quality--Physical and biological soil crusts (Soil Quality Information Sheet, Rangeland Sheet 7)
Publication TypeGovernment Report
Year of Publication2001
AuthorsShaver P.L, Tugel A.J., Herrick JE, Pellant M.
PublisherUSDA, Natural Resources Conservation Service
ARIS Log Number142796
Keywordsgovernment publication
AbstractA physical crust is a thin layer with reduced porosity and increased density at the surface of the soil. A biological crust is a living community of lichen, cyanobacteria, algae, and moss growing on the soil surface and binding it together. A chemical crust or precipitate is white or pale colored and forms in soils with a high content of salts. Both chemical and biological crusts can form on and extend into a physical crust. This information sheet deals only with physical and biological crusts. Physical crusts form when organic matter is depleted from the surface layer, soil aggregates become weak, and raindrops disperse the soil into individual particles that clog soil pores, seal the surface, and form a layer that is dense when dry. The development of objectives relative to soil crusts is an important part of rangeland management. Biological crusts protect the soil from water erosion and wind erosion. Physical crusts can protect soils from wind erosion as effectively as biological crusts, except on very coarse textured soils. In the more humid areas, it generally is desirable to break up physical crusts and thus improve seedling emergence and plant establishment; however, desirable biological crusts can be destroyed when the physical crusts are broken. Adequate organic matter, seeds of desirable species, and a period of rest are needed for successful establishment of plants after crusts are broken. The following management strategies apply to land used for grazing, wildlife habitat, or recreation: (1) Maintain the optimum amount of live vegetation, litter, and biological crust relative to the site potential in order to maintain the content of organic matter and soil structure and control erosion. (2) In humid areas improve soil structure and plant establishment by incorporating organic matter into the soil while breaking up a physical crust. (3) Defer grazing and recreational use during periods when biological crusts are most susceptible to physical disturbances. (4) Use prescribed burning according to the needs of each site to prevent fuel buildup that can produce hot fires followed by severe erosion. (5) Control the establishment and spread of invasive annual plants that can carry fire.
Government BodySoil Quality Institute, Grazing Lands Technology Institute, and National Soil Survey Center, Natural Resources Conservation Service, USDA; the Jornada Experimental Range, Agricultural Research Service, USDA; and Bureau of Land Management, USDI