soil map units where D Dark undifferentiated is dominant
Soil properties
| Property | Value |
|---|---|
| Geographic distribution | Tuvalu |
| Landscape position | Typically associated with the interior part of the islands, particularly the larger more compact islands. Often there is a gradual transition from light to dark soils away from the coast, although in places there is an abrupt break associated with a landform or vegetation change. Different textures not mapped. |
| Soil parent material | Coralline sand and gravel |
| Slope | Flat (0-3°) |
| Surface outcrops | No surface outcrops |
| Brief soil profile description | Deeper profiles often with two horizons - a brown or grey black surface horizon 5-15cm thick with a lighter stained zone below, which grades into unaltered sands and gravels. Topsoil colours are typically brown (7 .5YR 4/3) or dark brown (7.SYR 3/3), and relatively rich in decomposed organic matter which gives the soils developed on a sandy parent material a loamy texture. |
| Soil profile texture | Deeper organic accumulation over unaltered corraline sand and gravel. |
| Minimum effective rooting depth | >75 cm |
| Soil pH (acidity) | pH ranges over 7.7-8.4 (moderately alkaline) |
| Salinity | Low |
| Soil fertility under natural conditions | Most soil properties are related to the organic matter content of the topsoil. Organic Carbon, Nitrogen, Cation Exchange Capacity all increase with the age of the soil, but Potassium is always low. Extractable phosphorus (Olsen P) values are generally low for topsoils and very low for subsoils. |
| Soil moisture regime | Ustic |
| Susceptibility to drought | Susceptibly to drought during dry periods but these are relatively rare, particularly in the southern islands. |
| Soil drainage | Excessively drained |
| Susceptibility to waterlogging | Not susceptible |
| Susceptibility to flooding | Not susceptible |
