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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 relatively low rate of change indicates when macropore drainage ceases, which is called Field Capacity; it is also termed drained upper limit (DUL). Lorenzo A. Richards and Weaver [5] found that water content held by soil at a potential of −33 kPa (or −0.33 bar) correlate closely with field capacity (−10 kPa for sandy soils).
The specific heat of soil increases as water content increases, since the heat capacity of water is greater than that of dry soil. [89] The specific heat of pure water is ~ 1 calorie per gram, the specific heat of dry soil is ~ 0.2 calories per gram, hence, the specific heat of wet soil is ~ 0.2 to 1 calories per gram (0.8 to 4.2 kJ per ...
The Atterberg limits are a basic measure of the critical water contents of a fine-grained soil: its shrinkage limit, plastic limit, and liquid limit. Depending on its water content, soil may appear in one of four states: solid, semi-solid, plastic and liquid. In each state, the consistency and behavior of soil are different, and consequently so ...
The maximum rate at that water can enter soil in a given condition is the infiltration capacity. If the arrival of the water at the soil surface is less than the infiltration capacity, it is sometimes analyzed using hydrology transport models, mathematical models that consider infiltration, runoff, and channel flow to predict river flow rates ...
Water moves through soil due to the force of gravity, osmosis and capillarity. At 0 to 33 kPa suction (field capacity), water is pushed through soil from the point of its application under the force of gravity and the pressure gradient created by differences in the pressure of water; this is called saturated flow. At higher suction, water ...
Since plants require a nearly continuous supply of water, but most regions receive sporadic rainfall, the water-holding capacity of soils is vital for plant survival. [25] Soils can effectively remove impurities, [26] kill disease agents, [27] and degrade contaminants, this latter property being called natural attenuation. [28]