Soil moisture

Soil moisture is the water contained in soil pores and on soil particles. Its amount and availability depend on soil properties, weather, vegetation, and drainage.

Field capacity: The soil water content remaining after excess gravitational water has drained from saturated soil. It marks the upper limit of water commonly retained for plant use.
Soil texture: The relative proportions of sand, silt, and clay in soil. Particle size strongly affects pore sizes and water retention.
Irrigation scheduling: The practice of deciding when and how much to irrigate crops. Soil moisture measurements can indicate when irrigation is needed.
Agricultural drought: A water shortage in the root zone that limits crop or pasture growth. Persistently inadequate soil moisture is a direct driver of this drought type.
Volumetric water content: The volume of water in a soil sample divided by the sample's total volume. It quantifies moisture as a fraction of soil volume, rather than by water availability.
Permanent wilting point: The soil water content at which plants can no longer recover turgor after wilting. It marks the lower limit of water plants can extract.
Soil structure: The arrangement of soil particles into aggregates and the pores between them. Pore arrangement controls storage, drainage, and access to water.
Soil moisture sensor: An instrument that estimates the water content or water potential of soil. Sensors provide in-place measurements for irrigation and environmental monitoring.
Soil respiration: The release of carbon dioxide from soil through root and microbial metabolism. Soil water content can constrain the organisms and roots producing this carbon flux.
Gravimetric water content: The mass of water in a soil sample divided by the mass of its dry soil. It expresses moisture by mass, unlike volume-based soil water measures.

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