The non-limiting water range (NLWR) represents the range of
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 ...
in the
soil
Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former te ...
where limitations to plant growth (such as
water potential
Water potential is the potential energy of water per unit volume relative to pure water in reference conditions. Water potential quantifies the tendency of water to move from one area to another due to osmosis, gravity, mechanical pressure and mat ...
, air-filled
porosity
Porosity or void fraction is a measure of the void (i.e. "empty") spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%. Strictly speaking, some tests measure ...
, or soil strength) are minimal. John Letey (1985) from
UC Riverside
The University of California, Riverside (UCR or UC Riverside) is a public land-grant research university in Riverside, California. It is one of the ten campuses of the University of California system. The main campus sits on in a suburban distr ...
introduced the NLWR concept in an attempt to integrate several physical properties associated with plant or
root
In vascular plants, the roots are the organs of a plant that are modified to provide anchorage for the plant and take in water and nutrients into the plant body, which allows plants to grow taller and faster. They are most often below the sur ...
growth to refine the concept of
available water capacity. Alvaro Pires da Silva, Bev Kay. and Ed Perfect (
University of Guelph
, mottoeng = "to learn the reasons of realities"
, established = May 8, 1964 ()As constituents: OAC: (1874) Macdonald Institute: (1903) OVC: (1922)
, type = Public university
, chancellor ...
, Ontario) (1994) refined the concept and termed it ''least limiting water range'' (LLWR).
The upper limit (wet end) of LLWR is determined not only at water content 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 ...
(FC), but also the capability of providing adequate aeration for plant roots (usually taken as a minimum air filled porosity of 10%).
The upper limit is then defined as:
min q .
Rather than air-filled porosity at 10%, LaoSheng Wu from
UC Riverside
The University of California, Riverside (UCR or UC Riverside) is a public land-grant research university in Riverside, California. It is one of the ten campuses of the University of California system. The main campus sits on in a suburban distr ...
proposed moisture content where Oxygen
gas diffusion rate ODR value of 0.2 micro-g/cm2/min as criteria for satisfactory aeration status.
The lower limit (dry end) is not only limited to
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 ...
(PWP) but also the ability of root penetration. This is measured as soil mechanical resistance taken at an arbitrary value, say penetration at 3 MPa.
The lower limit is defined as:
max q {mechanical resistance = 3 MPa, PWP}.
See also
*
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 ...
*
Irrigation scheduling Irrigation scheduling is the process used by irrigation system managers to determine the correct frequency and duration of watering.
The following factors may be taken into consideration:
* Precipitation rate of the irrigation equipment – how q ...
*
Limiting factor
A limiting factor is a variable of a system that causes a noticeable change in output or another measure of a type of system. The limiting factor is in a pyramid shape of organisms going up from the producers to consumers and so on. A factor not l ...
*
Moisture equivalent Moisture equivalent is proposed by Lyman Briggs and McLane (1910) as a measure of field capacity for fine-textured soil materials.
Moisture equivalent is defined as ''the percentage of water which a soil can retain in opposition to a centrifugal f ...
*
Moisture stress Moisture stress is a form of abiotic stress that occurs when the moisture of plant tissues is reduced to suboptimal levels. Water stress occurs in response to atmospheric and soil water availability when the transpiration rate exceeds the rate of w ...
*
Pedotransfer function In soil science, pedotransfer functions (PTF) are predictive functions of certain soil properties using data from soil surveys.
The term ''pedotransfer function'' was coined by Johan Bouma as ''translating data we have into what we need''. The mo ...
*
Soil plant atmosphere continuum
The soil-plant-atmosphere continuum (SPAC) is the pathway for water moving from soil through plants to the atmosphere. Continuum in the description highlights the continuous nature of water connection through the pathway. The low water potential of ...
References
* Da Silva A P, Kay B D and Perfect E 1994 Characterization of the least limiting water range of soils. Soil Sci. Soc. Am. J. 58, 1775-1781.
* Letey J 1985 Relationship between soil physical properties and crop production. Adv. Soil Sci. 1, 277-294.
Soil physics