National Land Suitability Framework · Kingdom of Saudi Arabia · Module 3 of 4
Land Suitability — for a Named Crop
Capability asks whether land can support farming at all. Suitability asks how well one specific crop would do on it. The same measurements are read again — this time against each crop's own tolerance, not a general threshold. The class is always set by the single worst factor, never an average.
Diagnostic Factors
26 · 6 groups
Classes
S1 → S2 → S3 → N1 → N2
Systems
8 production systems
Framework
FAO Bulletin 55 · ALUES
01 · Capability vs Suitability
Same measurement, a crop-specific ruler
Suitability re-measures nothing. It re-reads capability's outputs against a crop's tolerance table — so the same hectare can be S2 for date palm and S3 for tomato.
CAPABILITY ASKS
Is this measurement a problem for farming in general? A general physical threshold. One class per hectare, any land use.
SUITABILITY ASKS
Is this a problem for this named crop? A crop tolerance table. One class per hectare per crop.
Why 26 factors here, 17 in capability. Suitability re-reads every land quality against a crop's tolerance and adds crop-only requirements that don't exist at the capability stage — irrigation demand, crop nutrient requirement, and chemical factors that only bite at crop-specific thresholds. The larger count is the design, not an inconsistency.
02 · The Diagnostic Factors
Twenty-six factors, six groups
ASoil Physicals6
- Available Water Capacity
- Soil Workability
- Rooting Conditions
- Surface Sealing & Crusting
- Soil Texture
- Coarse Fragments
BSoil Chemicalz n6
- Salinity (ECe)
- Sodicity (ESP/SAR)
- Toxicity Risk (Boron)
- Calcium Carbonate
- Gypsum Content
- Soil pH
CWater & Drainagew f3
- Drainage Condition
- Flood Hazard
- Waterlogging Risk
DTopography & Erosiont e d4
- Terrain Workability
- Water Erosion
- Wind Erosion
- Sand Encroachment
EClimatec5
- Moisture Deficit
- Thermal Suitability
- Radiation & Solar
- Length of Growing Period
- Frost Risk
FCrop-Specifici n2
- Irrigation Demand (ETc) ★
- Crop Nutrient Requirement
03 · The Result Classes
Five classes, worst factor decides
S1Highly suitableNo significant limitation for the crop.
S2Moderately suitableMinor limitations; yield somewhat reduced.
S3Marginally suitableSerious limitations; marginal returns.
N1Currently not suitableLimitations that could be overcome in time.
N2Permanently not suitableLimitations that cannot be economically corrected.
Subclass letters — the group, not the factor
s soil physicalz salinityn nutrientw waterf floodt terraine erosiond sand driftc climatei irrigation ★
A result reads S3s on the map, and "S3 — limited by rooting depth" in the zone record. The letter travels on the map; the exact factor is named in the location detail.
04 · The Eight Production Systems
The same crop, assessed differently by how it's grown
A crop's suitability depends on its production system — which factors even apply. Protected agriculture lifts the crop out of the soil, removing 16 of 26 factors; rain-fed farming drops irrigation demand but makes rainfall decisive. The numbers show governs · not-applicable · conditional for each system.
Irrigated Open-Field24 gov · 0 n/a · 2 cond
Soil chemistry + terrain — roots in native profile, pivot needs flat ground.
Orchard & Perennial22 gov · 1 n/a · 3 cond
Rooting depth + frost timing — one badly-timed frost costs the year's fruit.
Protected Agriculture8 gov · 16 n/a · 2 cond
Energy cost — frost & heat set the heating/cooling bill that decides viability.
Rain-fed & Supplementary23 gov · 2 n/a · 1 cond
Rainfall + growing window — nothing can be added to make up a shortfall.
Livestock & Grazing0 gov · 0 n/a · 0 cond
Forage productivity & water access — a different quality set (§11.21).
Aquaculture0 gov · 0 n/a · 0 cond
Water quality & supply — routed here from CNz, outside the 26.
Agro-industry0 gov · 0 n/a · 0 cond
Site logistics & access — a production-system extension.
Land Management0 gov · 0 n/a · 0 cond
Hazards qualify not disqualify — severe erosion is the reason to choose the site.
05 · How a Factor Applies
Four marks in the matrix
●GovernsRead, and can limit the crop. A bad reading sets the class on its own — soil salinity for open-field tomato.
○Does not applyMeasured but irrelevant here — soil salinity for greenhouse crops in substrate.
◖Qualifies — a bad reading is a good signThe hazard qualifies the land. Severe wind erosion is the reason to choose a dune-stabilisation site. Land management only.
▲ConditionalDepends on crop or setup — flood hazard is a constraint for rain-fed cropping, but spate irrigation farms the flood.
Suitability is the fourth question — asked only after capability, water and legal gates all open. It is the one answer that changes per crop.