National Land Capability Framework · Kingdom of Saudi Arabia · The Seventeen Land Qualities
Land Capability — The Land Qualities
The seventeen inherent land qualities assessed on every hectare, grouped into five families. Each is measured against its own C1–CN thresholds; the most severe becomes the hectare's class. Soil-based qualities read the profile below; terrain and climate read the surface and the sky. Every quality carries a code, a unit, and a subclass letter.
Land Qualities
17 assessed
Groups
5 families
Notation
LQ codes · 9 subclass letters
Output
C1 / C2 / C3 / C4 / CN
ASoil Physicals4
What the soil is physically made of and how deep roots can go. These qualities are largely permanent — you cannot change a soil's texture or its depth to bedrock at field scale, so they set the ceiling on what the land can do. We need to know how much water the soil can hold, how easily it can be worked, how deep roots can reach, and whether the surface seals over after rain.
LQ-SP-01
Available Water Capacitymm/m
The volume of water held in the soil profile that is accessible to plant roots. Derived from texture, depth, bulk density and organic matter content.
LQ-SP-02
Soil Workability%
The ease with which the soil can be cultivated, tilled and managed with agricultural machinery. Determined by texture, gravel content, surface stoniness, moisture conditions and soil structure.
LQ-SP-03
Rooting Conditionscm
The depth and quality of the soil profile available for root penetration. Restricted by bedrock, hardpan, duripan, strongly indurated calcium carbonate (calcrete) layers, or high gravel content.
LQ-SP-04
Surface Sealing & Crusting Risk%
The tendency of the soil surface to seal under raindrop impact or irrigation, forming a physical crust that reduces infiltration, promotes runoff, and impedes seedling emergence.
BSoil Chemicalz n4
What is dissolved in the soil and whether it helps or harms the crop. Some of this can be managed with amendments; some cannot. We need to know how salty the soil is, whether sodium has broken down its structure, whether it can hold and supply nutrients, and whether toxic elements like boron or chloride are present at harmful levels.
LQ-SC-01
Salinity HazarddS/m
The risk of soil salt accumulation to levels that reduce crop yield or prevent establishment. Determined by current ECe, drainage class, groundwater salinity, and irrigation water quality.
LQ-SC-02
Sodicity Hazard%
Risk of exchangeable sodium accumulation causing dispersion of clay particles, destruction of soil structure, and severe reduction in hydraulic conductivity. Assessed by ESP and SAR.
LQ-SC-03
Nutrient Availability & Retentioncmol/kg
The capacity of the soil to supply and retain plant-available nutrients. Determined by pH, organic matter, CEC, calcium carbonate content, and baseline NPK levels. Critically affected by phosphate fixation in calcareous soils.
LQ-SC-04
Toxicity Risk (B, Cl, CaCO₃)mg/L
Risk of ion toxicity at concentrations that injure plant tissues or inhibit growth. Key toxicants in the Al Lith context are boron (from geothermal groundwater), chloride (from sea intrusion), and excess calcium carbonate (lime-induced chlorosis).
Reference · Soil Profile
The horizons the soil qualities read
The soil-physical and soil-chemical qualities are measured through the profile — texture and rooting depth to the restricting layer, salinity and toxicity through the root zone. Water & drainage read how water moves within it. Topography and climate read the surface and the sky above.
CWater & Drainagew f3
How water behaves once it reaches the land — not whether water is available to irrigate, which is assessed separately. We need to know whether excess water drains away in time, whether the land floods from wadis or runoff, and whether the root zone stays waterlogged long enough to suffocate the crop.
LQ-W-01
Drainage Conditionclass
The natural ability of the soil and terrain to remove excess water from the root zone within an acceptable timeframe. Poor drainage leads to waterlogging, oxygen deficiency, nutrient loss, and root disease.
LQ-W-02
Flood Hazardevents/10yr
The frequency, duration and depth of floodwater inundation from wadi channels or surface runoff. Assessed as the statistical return period of damaging flood events.
LQ-W-03
Waterlogging Riskdays/yr
The risk of temporary or permanent saturation of the root zone due to shallow water table, perched water tables above restricting layers, or insufficient drainage capacity during irrigation or flooding events.
DTopography & Erosiont e d4
The shape of the land and whether it is losing soil. Slope decides what machinery can work and how fast water runs off; erosion and sand movement decide whether the topsoil stays put. We need to know how steep and workable the terrain is, how much soil is lost to water and to wind, and whether moving dunes threaten to bury the site.
LQ-T-01
Terrain Workability%
The suitability of the terrain for agricultural machinery and field operations. Determined by slope gradient, slope length, surface roughness, and microrelief characteristics.
LQ-T-02
Water Erosion Hazard%
The risk of topsoil loss by water erosion from rainfall and runoff. Determined by rainfall erosivity, slope gradient and length, soil erodibility, and surface cover. High erosion rates remove irreplaceable topsoil and nutrients.
LQ-T-03
Aeolian (Wind) Erosion Hazardt/ha/yr
The risk of soil loss and sand encroachment from wind action. Determined by wind erosivity, soil erodibility (fine particles), surface cover, and proximity to active dune fields.
LQ-T-04
Sand Encroachment Hazardm/yr
The rate and directional advance of mobile sand onto a site from an upwind dune source, creating burial and abrasion hazard. Distinct from wind erosion: this is material arriving from elsewhere, not soil leaving the site.
EClimatec2
The absolute climate of the site — true whatever is planted. These set the outer limits of what the sun and heat allow. We need to know whether there is enough accumulated warmth across the year for crops to complete their cycle, and whether solar radiation is strong enough to drive good photosynthesis.
LQ-C-01
Thermal SuitabilityGDD
The match between the temperature regime and the thermal requirements of agricultural crops. Assessed by growing degree days (GDD), mean temperature during the growing season, and frequency of heat stress or frost events. For national KSA use: the current single-rating thermal assessment adequately captures coastal and lowland conditions. For Asir highlands and Al-Baha, where frost risk is a real constraint, and for date palm cultivation where chilling accumulation is a positive requirement as well as heat-unit accumulation, sub-component calibration (frost frequency, heat units, chilling hours) should be applied during national threshold calibration. The current thresholds are illustrative pending national calibration.
LQ-C-02
Radiation & Solar Energy AvailabilityMJ/m²/d
The quantity and seasonal distribution of solar radiation available for photosynthesis and energy generation. Expressed as Global Horizontal Irradiance (GHI) in kWh/m2/day. A positive capability asset in the Al Lith context.
C1C2C3C4CN
17 land qualities · 5 groups · each measured to its own C1–CN thresholds · maximum-limitation rule
Tec Solution
Prepared for the Ministry of Environment, Water and Agriculture