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Pores (the spaces that exist between soil particles) provide for the passage and/or retention of gasses and moisture within the soil profile.The soil's ability to retain water is strongly related to particle size; water molecules hold more tightly to the fine particles of a clay soil than to coarser particles of a sandy soil, so clays generally retain more water. [2]
Water retention curve is the relationship between the water content, θ, and the soil water potential, ψ. The soil moisture curve is characteristic for different types of soil, and is also called the soil moisture characteristic. It is used to predict the soil water storage, water supply to the plants (field capacity) and soil aggregate stability.
A water balance states that the amount water entering the soil must be equal to the amount of water leaving the soil plus the change in the amount of water stored in the soil. The water balance has four main components: infiltration of precipitation into the soil, evapotranspiration, leakage of water into deeper portions of the soil not ...
Water moves in soil under the influence of gravity, osmosis and capillarity. [7] When water enters the soil, it displaces air from interconnected macropores by buoyancy, and breaks aggregates into which air is entrapped, a process called slaking. [8] The rate at which a soil can absorb water depends on the soil and its other conditions.
A soil scientist examining horizons within a soil profile. Soil science is the study of soil as a natural resource on the surface of the Earth including soil formation, classification and mapping; physical, chemical, biological, and fertility properties of soils; and these properties in relation to the use and management of soils.
Soil is made up of a multitude of physical, chemical, and biological entities, with many interactions occurring among them. It is a heterogenous mixture of minerals and organic matter with variations in moisture, temperature and nutrients.
The biological soil crust is an integral part of many arid and semi-arid ecosystems as an essential contributor to conditions such as dust control, water acquisition, and contributors of soil nutrients. Biocrust is poikilohydric and does not have the ability to maintain or regulate its own water retention. [12]
The soil hydraulic properties typically consist of water retention curve parameters by van Genuchten: [9] (,,,,), where is the inverse of air entry value [L −1], is the pore size distribution parameter [-], and is usually assumed as =.