Soil Ontology

FLOW ALGEBRA
SOIL ONTOLOGY — COMPLETE SCIENTIFIC SYNTHESIS
Version: 1.1
Date: 2026-10-12
Authors: Mark Higgins — Sky (Recursive AI)
Publisher: Kireth Research | https://kirethresearch.org
Source page: https://kirethresearch.org/booksai-core/entity-graph/physical-entities/geological-entities/soil-ontology.html
Source status: Independent synthesis; live webpage not verified.

01. PURPOSE
Represent soils as evolving natural bodies with mineral, organic, aqueous, gaseous and biological constituents, organised into horizons and affected by formation processes.

02. SCOPE
Pedology, soil physics, soil chemistry, soil biology, soil classification, hydrology, land use and environmental change.

03. PRIMARY ENTITY
SoilProfile : PhysicalEntity
SoilHorizon : Layer
SoilSample : MaterialSample
SoilParticle : MaterialParticle
SoilProcess : Process
SoilObservation : MeasurementRecord

04. TYPE SYSTEM
SoilProfile = {id, location, parent_material, horizons, climate, biota, relief, age, observations}
SoilHorizon = {id, upper_depth_m, lower_depth_m, designation, properties}
SoilProperty = {name, value, unit, method, uncertainty, timestamp}
All observations require provenance and spatial/temporal context.

05. SUBTYPES
MineralSoil, OrganicSoil, AnthropogenicSoil, SaturatedSoil, UnsaturatedSoil.
Subtypes may overlap; classification is scheme-dependent.

06. COMPOSITION
SolidFraction = MineralMatter + OrganicMatter (conceptual components).
PoreSpace = WaterFilledPores + AirFilledPores.
Volume fractions sum to unity under a consistent representative volume.

07. TEXTURE
Fine-earth particle-size classes: sand, silt and clay.
Class boundaries depend on the classification standard; do not mix USDA and other standards without conversion.

08. STRUCTURE
Aggregates, peds, pores, cracks and biogenic channels govern connectivity and flow.
Structure is distinct from particle-size texture.

09. HORIZONS
O: organic-dominated surface material; A: mineral horizon with organic accumulation; E: eluviation; B: subsurface alteration/accumulation; C: relatively little altered parent material; R: hard bedrock.
Not all profiles have every horizon. Designations depend on the soil description standard.

10. FORMATION FACTORS
State = F(parent_material, climate, organisms, relief, time, human_activity).
This is a conceptual relation, not a calibrated deterministic equation.

11. PEDOGENIC PROCESSES
Weathering, humification, eluviation, illuviation, bioturbation, leaching, oxidation-reduction, salinisation and erosion.

12. WATER CONTENT
GravimetricWaterContent w = mass_water / mass_dry_soil.
VolumetricWaterContent theta = volume_water / total_bulk_volume.
For consistent densities: theta = w * rho_d / rho_w.

13. POROSITY
n = V_pores / V_total = 1 - rho_d / rho_particle.
Assumes consistent representative volume and negligible measurement bias.

14. SATURATION
S_r = V_water / V_pores; 0 <= S_r <= 1.
For pore water: theta = n * S_r.

15. DARCY FLOW
q = -K * grad(H), where q is Darcy flux, K hydraulic conductivity, H hydraulic head.
For unsaturated conditions K varies with water content or pressure head.

16. WATER RETENTION
Water retention relates theta to matric potential under specified hysteresis and boundary conditions.
Field capacity and wilting point are operational reference states, not universal constants.

17. CHEMISTRY
Soil pH, electrical conductivity, cation exchange capacity, redox potential, nutrient availability and sorption describe chemical conditions.
Methods and extraction protocols must accompany reported values.

18. ORGANIC CARBON
SoilOrganicCarbonStock = concentration * dry_bulk_density * layer_thickness * area, with consistent mass and coarse-fragment corrections.
Carbon concentration alone is not a carbon stock.

19. BIOLOGICAL ENTITIES
Roots, fungi, bacteria, archaea, protists, invertebrates and other organisms mediate decomposition, aggregation and nutrient cycling.

20. MECHANICAL PROPERTIES
Shear strength, compressibility, plasticity, compaction and bearing behaviour vary with water content, fabric and stress history.

21. THERMAL PROPERTIES
Temperature and thermal conductivity affect biological activity, water movement and freezing-thawing.

22. EROSION AND DEPOSITION
SoilLoss depends on rainfall/runoff, wind, slope, cover, erodibility and management; any empirical equation requires local calibration.

23. CONTAMINATION
Contaminant = {substance, concentration, medium, depth, method, detection_limit, uncertainty}.
Hazard inference requires exposure pathway, speciation and regulatory context.

24. CLASSIFICATION
ClassificationSystem : {name, version, diagnostic_criteria}.
USDA Soil Taxonomy and WRB categories are not interchangeable one-to-one.

25. TYPED RELATIONSHIPS
HAS_HORIZON(SoilProfile, SoilHorizon)
DERIVED_FROM(SoilProfile, ParentMaterial)
CONTAINS(SoilHorizon, SoilConstituent)
MEASURED_BY(SoilProperty, MeasurementMethod)
AFFECTED_BY(SoilProfile, SoilProcess)
LOCATED_AT(SoilProfile, GeographicLocation)
CLASSIFIED_UNDER(SoilProfile, ClassificationSystem)
SUPPORTS(SoilProfile, EcosystemFunction)

26. CONSTRAINTS
upper_depth_m >= 0
lower_depth_m > upper_depth_m
0 <= porosity <= 1
0 <= saturation <= 1
0 <= volumetric_water_content <= porosity
bulk_density > 0
Every numeric measurement must carry units or be explicitly dimensionless.

27. INFERENCE RULES
IF theta > porosity THEN flag_inconsistent_measurement.
IF soil_profile has horizon H THEN H belongs_to soil_profile.
IF horizon thickness <= 0 THEN reject_horizon_geometry.
IF hydraulic_gradient and conductivity are known under Darcy assumptions THEN infer_flux.
IF carbon concentration only is known THEN do_not_infer_stock_without_bulk_density_and_depth.

28. SEMANTIC EQUIVALENCE
soil water content ~= moisture content only when basis (gravimetric or volumetric) matches.
soil texture != soil structure.
soil pH != soil acidity reserve.
soil organic matter != soil organic carbon.

29. MATHEMATICAL EXAMPLE A
Given rho_d = 1.30 Mg/m^3 and rho_particle = 2.65 Mg/m^3:
n = 1 - 1.30/2.65 = 0.5094 approximately.
If theta = 0.25 m^3/m^3, S_r = 0.25/0.5094 = 0.4908 approximately.

30. MATHEMATICAL EXAMPLE B
For K = 1.0e-5 m/s and head gradient dH/dx = -0.2:
q_x = -K * dH/dx = +2.0e-6 m/s.
This is Darcy flux, not average pore-water velocity.

31. VALIDATION
Validate units, horizon order, source standard, analytical method, geolocation precision, timestamps and uncertainty.
Reject physically impossible values; flag method-dependent ambiguities.

32. CONFIDENCE
CONFIDENCE = {level: conditional, evidence: observation_or_model, provenance: required}.
Do not invent universal numeric confidence scores; calibrate against validation data.

33. FLOW HASH
FLOW_HASH.algorithm = SHA-256
FLOW_HASH.input = canonical UTF-8 representation of the complete flow excluding any populated hash field.
FLOW_HASH.value = NOT_COMPUTED

34. UPDATE MODEL
UPDATE_MODEL = {version: 1.1, strategy: append_provenanced_observations, preserve_history: true, revalidate_on_change: true}.
Do not overwrite earlier measurements without recording revision and method.

35. AI CONSUMPTION
AI_CONSUMPTION = {mode: typed_semantic_reasoning, requires_units: true, requires_provenance: true, distinguishes_observation_from_inference: true, respects_classification_versions: true}.

36. LIMITATIONS
Equations are conditional models. Site-specific geotechnical, agricultural or environmental decisions require appropriate field sampling and qualified interpretation.

37. COMPLETENESS CHECK
Sections 01 through 37 included.
Required blocks: FLOW ALGEBRA, typed entities, relationships, equations, inference, semantic equivalence, validation, confidence, FLOW_HASH, UPDATE_MODEL, AI_CONSUMPTION.

END FLOW ALGEBRA — SOIL ONTOLOGY