National Land Capability Framework · Kingdom of Saudi Arabia · All 13 Regions
KSA National Land Capability
A national evaluation of the inherent physical limitations of agricultural land, based on UN/FAO parameters. Capability describes what the land can physically support — independent of any specific crop. Classification follows the C1–CN hierarchy with limiting-factor subclasses. Water supply is assessed separately, as a national resource allocation decision.
Framework
FAO Bulletin 32 & 2007 Rev.
Groups
5 land-quality groups
Land Qualities
19 assessed
Output
C1 / C2 / C3 / C4 / CN
01 · The Land Qualities
Nineteen qualities, five groups
Each group holds the qualities of one kind of limitation. A subclass letter names the family, so a class carries the reason for it.
ASoil Physical4 · s
Inherent physical properties — largely permanent, not correctable at field scale.
s — soil
BSoil Chemical4 · z n
Nutrient availability, ion toxicity, salinity — semi-permanent, some manageable by amendment.
z — salinity/sodicityn — nutrient/toxicity
CWater & Drainage3 · w f
Movement and retention of water on the land — drainage, flood, waterlogging. Water supply is separate.
w — water/wetnessf — flood
DTopography & Erosion4 · t e d
Terrain, workability, erosion, sand movement — permanent; slope cannot be changed at scale.
t — topographice — erosiond — sand drift
EClimate4 · c
Absolute climate properties — thermal, radiation, moisture, growing period — true whatever is planted.
c — climate
02 · The Class Scheme
Five classes, C1 to CN
C1Highly capableEvery governing quality favourable.
C2Moderately capableNo severe limitation; at least one moderate.
C3Marginally capableOne severe limitation, documented as improvable.
C4Currently not capableSeveral severe limitations, all improvable.
CNNot capableA severe limitation that is not improvable.
A worked quality
LQ-SP-01 · Group A
Available water capacity
How much water the soil holds for the plant between waterings — mm/m, higher is better.
147 mm/m falls in band C1. Every quality is rated this way against its own thresholds — the assessment stops at the band.
03 · How the Class is Decided
Every quality is rated. The worst one becomes the class.
FAO Bulletin 32 defines the classes but not the arithmetic. This study uses maximum limitation — a severe constraint is not offset by favourable conditions elsewhere.
1
Rate each qualityAll 19 qualities scored against their own C1–CN thresholds.
2
Each group takes its worstThe group's class is the most severe of its members.
3
The hectare takes the worst groupThe most severe of the five group classes becomes the hectare's class.
4
The subclass records whyC4s is class 4, limited by a soil-physical quality.
Core FAO principle. The capability of the land is determined by its most severe limitation, not by its average condition. The final class reflects the worst single constraint, however many positive qualities the land holds — so any class can be checked by finding its one worst quality.
The nine subclass letters
s soilz salinityn nutrient
w wetnessf floodt topography
e erosiond sand driftc climate
04 · Why Maximum Limitation, and Not an Average
A severe constraint is not compensated by good conditions elsewhere
Five combination methods exist in the land-evaluation literature. Limitation methods take the single worst constraint; parametric methods — Storie, square-root, Sys land index — convert each rating to a percentage and combine them arithmetically. This study applies maximum limitation deliberately, and the reasoning is decisive in an arid setting: a hectare that is excellent on sixteen qualities and severely saline is not "mostly excellent land" — it is saline land, and will farm as such.
Retained
Maximum limitation. Widely applied in arid-zone land evaluation. It keeps the severity of the worst constraint visible while letting secondary constraints moderate the subclass — the class is honest about what will actually limit the crop.
Set aside
Parametric averaging. The Storie and Sys indices blend all ratings into one figure — which can let strong qualities mask a fatal one. Appropriate where limitations trade off; misleading where one constraint is decisive, as salinity or slope is here.
The three methods that reach the correct class all do so because each is governed by the minimum. The chosen method resolves each group to the worst of its qualities, then the hectare to the worst of its groups — and the subclass letter records which group produced it.
05 · What Capability Excludes
What the land is — not what it needs
Capability holds only absolute properties of the ground. Three things a hectare needs to be farmed are assessed by other modules and reported alongside — never folded into the class.
WWater supply — availability, depletion, alternatives. Folding it in would mark almost all irrigated land not capable, because it draws on non-renewable aquifers.
ELegal status — protection, ownership, zoning. A separate answer, because a permanent bar and a paperwork gap must not look alike.
SCrop suitability — the same qualities re-read against one crop's tolerances. Capability asks if the land can be farmed at all; suitability asks how well a named crop does.
Capability is the first gate. It runs once per hectare, independent of crop and use, and produces one class and one subclass — the foundation every other module reads from.