Available water capacity is the amount of water that can be stored in a soil profile and be available for growing crops. It is also known as available water content (AWC), profile available water (PAW) or total available water (TAW).
The concept, put forward by Frank Veihmeyer and Arthur Hendrickson, assumed that the water readily available to plants is the difference between the soil
water content
Water content or moisture content is the quantity of water contained in a material, such as soil (called soil moisture), rock, ceramics, crops, or wood. Water content is used in a wide range of scientific and technical areas, and is expressed as ...
at
field capacity Field capacity is the amount of soil moisture or water content held in the soil after excess water has drained away and the rate of downward movement has decreased. This usually takes place 2–3 days after rain or irrigation in pervious soils of u ...
() and
permanent wilting point
Permanent wilting point (PWP) or wilting point (WP) is defined as the minimum amount of water in the soil that the plant requires not to wilt. If the soil water content decreases to this or any lower point a plant wilts and can no longer recover ...
():
:θ
a ≡ θ
fc − θ
pwp
Daniel Hillel criticised that the terms FC and PWP were never clearly defined, and lack physical basis, and that soil water is never equally available within this range. He further suggested that a useful concept should concurrently consider the properties of plant, soil and meteorological conditions.
Lorenzo A. Richards
Lorenzo Adolph Richards (April 24, 1904 – March 12, 1993) or known as ''Ren'' was one of the 20th century's most influential minds in the field of soil physics.
Biography Early life
Lorenzo A. Richards was born on April 24, 1904, in the town of ...
remarked that the concept of availability is oversimplified. He viewed that: the term availability involves two notions: (a) the ability of plant root to absorb and use the water with which it is in contact and (b) the readiness or velocity with which the soil water moves in to replace that which has been used by the plant.
Plant available water in sandy soils can be increased by the presence of
sepiolite
Sepiolite, also known in English by the German name meerschaum ( , ; ; meaning "sea foam"), is a soft white clay mineral, often used to make tobacco pipes (known as meerschaum pipes). A complex magnesium silicate, a typical chemical formula f ...
clay
[{{Cite journal , last=Francis , first=Michele Louise , date=2019 , title=Effect of sepiolite and palygorskite on plant available water in Arenosols of Namaqualand, South Africa , url=https://linkinghub.elsevier.com/retrieve/pii/S2352009418302207 , journal=Geoderma Regional , language=en , volume=17 , pages=e00222 , doi=10.1016/j.geodrs.2019.e00222]
See also
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Field capacity Field capacity is the amount of soil moisture or water content held in the soil after excess water has drained away and the rate of downward movement has decreased. This usually takes place 2–3 days after rain or irrigation in pervious soils of u ...
*
Integral energy
Integral energy is the amount of energy required to remove water from soil with an initial water content \theta_i to water content of \theta_f (where \theta_i > \theta_f). It is calculated by integrating the water retention curve, soil water poten ...
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Nonlimiting water range The non-limiting water range (NLWR) represents the range of water content in the soil where limitations to plant growth (such as water potential, air-filled porosity, or soil strength) are minimal. John Letey (1985) from UC Riverside introduced the ...
*
Permanent wilting point
Permanent wilting point (PWP) or wilting point (WP) is defined as the minimum amount of water in the soil that the plant requires not to wilt. If the soil water content decreases to this or any lower point a plant wilts and can no longer recover ...
References
Agricultural soil science
Water
Agrometeorology