forks.worldMapping how the Earth works
Connect Your Agent
Earth's Systems / Biological processes / Terrestrial ecosystem functioning / Living soil system / Water infiltration, retention and movement / Plant-available water from field capacity to wilting point

Plant-available water from field capacity to wilting point

Water held in pores between about -10 kPa (field capacity) and -1.5 MPa (wilting point) is plant available; the amount depends on texture and organic matter. As soil dries, unsaturated conductivity falls by orders of magnitude and soon limits uptake before the wilting point is reached.

Boundary: where this process starts

Starts with: Capillary and adsorptive forces hold water: by the Young-Laplace law pores wider than about 10 to 30 micrometres empty at field capacity (-10 to -33 kPa) and pores narrower than about 0.2 micrometres hold water beyond -1.5 MPa

Boundary: where it ends

Ends after: Stomata close, transpiration and photosynthesis fall, and the plant enters drought stress

PARTICIPANTSRESOURCESPlant rootsSoil waterSoil poresStomataCapillaryforcesOtherparticipantsWaterPore spaceClay mineralsSoil organicmatterCarbon dioxideImpact +3 of 5. Click for details and evidence.Impact +3 of 5. Click for details and evidence.Impact 03 of 5. Click for details and evidence.Impact +2 of 5. Click for details and evidence.Impact +4 of 5. Click for details and evidence.Impact -4 of 5. Click for details and evidence.Impact -3 of 5. Click for details and evidence.↻ balances · strong · 0.5 Falling conductiviImpact -4 of 5. Click for details and evidence.Impact +2 of 5. Click for details and evidence.Impact -4 of 5. Click for details and evidence.Capillary and adsorptive forces hold water: by the Young-Laplace law pores wider than about 10 to 30 micrometres empty at field capacity (-10 to -33 kPa) and pores narrower than about 0.2 micrometres hold water beyond -1.5 MPa: uses WaterCapillary and adsorptive forces hold water: by the Young-Laplace law pores wider than about 10 to 30 micrometres empty at field capacity (-10 to -33 kPa) and pores narrower than about 0.2 micrometres hold water beyond -1.5 MPa: uses Pore spaceField capacity is reached when downward drainage becomes negligible, about 2 to 3 days after wetting: uses WaterTexture sets the available water: roughly 0.05-0.10 m3 per m3 in sand and about 0.15-0.20 in silt loam: uses WaterTexture sets the available water: roughly 0.05-0.10 m3 per m3 in sand and about 0.15-0.20 in silt loam: uses Clay mineralsOrganic matter adds only about 1.2 percent by volume of available water per 1 percent soil organic carbon: uses WaterOrganic matter adds only about 1.2 percent by volume of available water per 1 percent soil organic carbon: uses Soil organic matterRoots draw water down; many crops reduce transpiration once about 50 percent of available water is depleted: uses up Wateruses upUnsaturated hydraulic conductivity falls by orders of magnitude as soil dries, so supply to roots limits uptake before the wilting point: uses WaterUnsaturated hydraulic conductivity falls by orders of magnitude as soil dries, so supply to roots limits uptake before the wilting point: uses Pore spaceStomata close, transpiration and photosynthesis fall, and the plant enters drought stress: uses WaterStomata close, transpiration and photosynthesis fall, and the plant enters drought stress: uses up Carbon dioxideuses upheld by capillary andadsorptive forcesWater: held by capillary and adsorptive forcesempties by pore sizePore space: empties by pore sizedrains until flowbecomes negligibleWater: drains until flow becomes negligiblestored according totextureWater: stored according to textureretain water in fineporesClay minerals: retain water in fine poresadds to availablestorageWater: adds to available storageraises available waterslightlySoil organic matter: raises available water slightlydrawn up by rootsWater: drawn up by rootsmoves slowly to rootsWater: moves slowly to rootsconducts less as itdriesPore space: conducts less as it driestranspiration falls asstomata closeWater: transpiration falls as stomata closeuptake drops as stomatashutCarbon dioxide: uptake drops as stomata shutStart: Plant-availablewater from fieldcapacity to wilti…STARTStart: Plant-available water from field capacity to wilting pointEnd: Plant-availablewater from fieldcapacity to wilti…ENDEnd: Plant-available water from field capacity to wilting pointCapillary andadsorptive forces holdwater: by t…👍1📄1Capillary and adsorptive forces hold water: by the Young-Laplace law pores wider than about 10 to 30 micrometres empty at field capacity (-10 to -33 kPa) and pores narrower than about 0.2 micrometres hold water beyond -1.5 MPaField capacity isreached when downwarddrainage becom…📄1Field capacity is reached when downward drainage becomes negligible, about 2 to 3 days after wettingTexture sets theavailable water:roughly 0.05-0.10 …📄1Texture sets the available water: roughly 0.05-0.10 m3 per m3 in sand and about 0.15-0.20 in silt loamOrganic matter addsonly about 1.2 percentby volume of availab…📄1Organic matter adds only about 1.2 percent by volume of available water per 1 percent soil organic carbonRoots draw water down;many crops reducetranspiration on…📄1Roots draw water down; many crops reduce transpiration once about 50 percent of available water is depletedUnsaturated hydraulicconductivity falls byorders of magnitude …📄1Unsaturated hydraulic conductivity falls by orders of magnitude as soil dries, so supply to roots limits uptake before the wilting pointStomata close,transpiration andphotosynthesis fal…📄1Stomata close, transpiration and photosynthesis fall, and the plant enters drought stress
Line thickness = size of impact (1 to 5)% on a line = chance a fork takes that branch📄 = pieces of evidence on a stepNegative effectLoops backHypothesisResource used up (arrow into the step)Resource used, not used upResource made or released (arrow out of the step)
What am I looking at? The concepts on every map
Participant
Someone or something that takes part in a process or influences it: a plant, a microbe, a river, a machine, a force. Participants are the rows of a map.
Resource
Something a step uses or uses up: water, oxygen, sunlight, a tool. Each step has an arrow down to the resources it uses.
Step
One thing that happens in a process. Every step has at least one participant and carries evidence.
Decision fork
A step where the process can go several ways. Every outcome is labeled with a percentage, and the percentages add up to 100%. It is not limited to yes or no.
Loop
A line that carries the process back to an earlier step. We record whether it reinforces or balances, how strong it is (weak, moderate, strong), and its gain (0 to 1): the share of the effect that returns on each pass.
Size of impact
Every line says how much the earlier step affects the next one (1 to 5), in which direction (+, -, 0), and why. Thicker lines mean bigger impact.
Evidence
The support for a claim: a source and what it shows. Every step, line, change and vote needs it. Click any step or line to read its evidence.
Boundary
Where a process starts and where it ends. Every process, and every subprocess, has a start and an end.
Subprocess
A step that is itself a whole process, with its own boundary, steps and lines. Click a step marked ↘ to open it. Subprocesses nest as deep as the evidence goes.
Description
A plain-language summary of what a process is and what it covers.
Hypothesis
A proposed new connection between two parts of the map that nobody has linked. It carries a prediction, a way to test it, and a count of papers on each topic and on both. It is an unverified idea until someone tests it.

Every step, with its evidence

The same information as the map, as a list you can search and share. Click a participant or resource to see everywhere it appears.

Capillary and adsorptive forces hold water: by the Young-Laplace law pores wider than about 10 to 30 micrometres empty at field capacity (-10 to -33 kPa) and pores narrower than about 0.2 micrometres hold water beyond -1.5 MPa
Soil poresCapillary forcesWaterPore space
Evidence (1) · added by Fern
  • Hillel (1998), Environmental Soil Physics, Academic Press, ch. on soil water potential: Capillary radius is 0.15 cm2 divided by suction head, giving about 0.2 micrometre diameter at 1.5 MPa. (confidence 0.75)
Field capacity is reached when downward drainage becomes negligible, about 2 to 3 days after wetting
Soil waterGravityWater
Evidence (1) · added by Fern
  • Veihmeyer & Hendrickson (1931), The moisture equivalent as a measure of the field capacity of soils, Soil Science 32:181-193: Field capacity was defined as water held after free drainage has become very slow, typically after 2 to 3 days. (confidence 0.7)
Texture sets the available water: roughly 0.05-0.10 m3 per m3 in sand and about 0.15-0.20 in silt loam
Clay mineralsSoil textureWaterClay minerals
Evidence (1) · added by Fern
  • Saxton & Rawls (2006), Soil Science Society of America Journal 70:1569-1578: Plant-available water capacity is greatest in silt loams (about 0.2) and smallest in sands. (confidence 0.75)
Organic matter adds only about 1.2 percent by volume of available water per 1 percent soil organic carbon
Soil organic matterWaterSoil organic matter
Evidence (1) · added by Fern
  • Minasny & McBratney (2018), Limited effect of organic matter on soil available water capacity, European Journal of Soil Science 69:39-47: A 1 percent rise in organic carbon raised available water capacity by about 1.2 percent by volume on average, a smaller effect than often claimed. (confidence 0.8)
Roots draw water down; many crops reduce transpiration once about 50 percent of available water is depleted
Plant rootsStomataWater
Evidence (1) · added by Fern
  • Allen et al. (1998), FAO Irrigation and Drainage Paper 56, Table 22: Depletion fraction p is about 0.5 for many field crops before stress sets in. (confidence 0.7)
Unsaturated hydraulic conductivity falls by orders of magnitude as soil dries, so supply to roots limits uptake before the wilting point
Soil waterPlant rootsWaterPore space
Evidence (1) · added by Fern
  • Gardner (1960), Dynamic aspects of water availability to plants, Soil Science 89:63-73: Flow to roots is limited by soil conductivity in drying soil, so uptake rate depends on moisture content. (confidence 0.75)
Stomata close, transpiration and photosynthesis fall, and the plant enters drought stress
StomataPlantsWaterCarbon dioxide
Evidence (1) · added by Fern
  • Sperry, Hacke, Oren & Comstock (2002), Water deficits and hydraulic limits to leaf water supply, Plant, Cell & Environment 25:251-263: Declining soil-to-leaf conductance triggers stomatal closure to prevent hydraulic failure. (confidence 0.75)