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Microbial biomass

The total amount of organisms in the soil, excluding macrofauna and plant roots. Microbial biomass is typically determined through substrate-induced respiration, or fumigation-extraction methods.


The conversion of organic compounds into inorganic, plant-available compounds such as ammonium. This is accomplished by soil organisms as they consume organic matter and excrete wastes. (See immobilization.)

Minimum data set (MDS)

The smallest set of soil properties that can be used to characterize or measure soil quality. The MDS will vary based on the intended land use, soil type, and climate. The first MDS was suggested by Larson and Pierce and included the following: nutrient availability, total organic C, particle size or texture, labile organic C, plant-available water capacity, soil structure, soil strength, maximum rooting depth, pH, and electrical conductivity.

Minimum tillage

A tillage system that limits tillage operations to those essential to crop production and prevention of soil damage, generally leaving about 30% crop residues on the surface, often executed with specific machines (e.g. harrow, cultivator with rigid tines or a rotavator), only once a year.

Moderately fine textured

Texture group consisting of clay loam, sandy clay loam and silty clay loam textures; see also soil texture.

Monitoring soil quality

Tracking trends in quantitative indicators or the functional capacity of the soil in order to determine the success of management practices or the need for additional management changes. Monitoring involves the orderly collection, analysis, and interpretation of data from the same locations over time. (Compare to assessing.)


The growing of a single arable crop species on a field year after year, for at least 10 years.


Representative vertical section taken from vertical face of a soil profile pit or section, which represents arrangement of soil horizons; there are various methods of how to take and conserve soil monoliths.


Photosynthetic plants with small leaves that unfurl when moistened (thus the moss appears to swell). When dry, mosses are dark and dull-colored; when moistened, the color changes markedly to a bright, light green to brown. This makes them easy to distinguish from lichens.


Organic residues left on top of the soil or in the first few cm of soil.

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