Suirbhidh agus Clasadh Laimhe

Study Notes

Purpose of Soil Survey: Soil survey aims to identify suitable areas for crops, management practices, and other specific uses. It also helps with land use planning, evaluating land for specific crops, land appraisal for taxation, rural land classification for irrigation/rain-fed crops, and selection for settlements/infrastructure projects.

Order: The highest level, differentiating soils based on major diagnostic horizons (presence/absence).
Suborder: Classifies based on moisture regimes, parent material, and vegetation.
Great Group: Classifies based on similarities in horizon characteristics (kind, arrangement, and degree of expression, particularly in the upper soil layer), base status, soil temperature, and moisture regimes (presence/absence of diagnostic layers).
Subgroup: Uses central concept taxa and intergradations to other Great Groups/Suborders/Orders.
Family: Differentiates based on important properties for plant growth (texture, mineralogy, soil temperature, and soil moisture).
Series: Lowest level, based on kind and arrangement of horizons.

Epipedon (Upper Horizon): Different types, including Mollic (soft, dark, high organic matter, base saturation > 50%), Anthropic (similar to mollic but with >250ppm citric acid soluble P2O5), Umbric (dark, base saturation < 50%), Histic (20-30% organic matter, water saturated for >30 days), Ochric (light color, low organic matter <1%), Plaggen (man-made surface horizon >50cm, manure addition).
Subsoil (Lower Horizon): Includes Argillic (higher clay content than layer above), Aeric, Natric (sodium saturation > 15%), Spodic (accumulation of free iron oxides and organic matter), Oxic (highly weathered, 1:1 clays prevalent).

Entisol: Very young soil, limited profile development.
Inceptisol: Young soil, moderate profile development.
Aridisol: Limited change in parent material, due to dryness.
Mollisol: Dark surface due to high organic matter.
Spodosol: Subsoil accumulation of Fe and Al oxides, humus, and amorphous clays.
Alfisol: Argillic B horizon with high base saturation.
Ultisol: High clay B horizon but low base saturation.
Oxisol: Highly weathered soil, B horizon mainly 1:1 clays (e.g., kaolinite).
Vertisol: Shows large cracks during drying, due to montmorillonite dominance.
Histosol: Organic soils.

Formative Elements: Many elements relating to different aspects of soil properties are used to form suborder names (e.g., Alb, And, Aqu, Ar, Arg, Bor, Ferr, Fibr, Fluv, Fol, Hem, Hum, Ochr, Orth, Plagg, Psamm, Rend, Sapr, Torr, Ud, Umbr, Ust, and Xer)

Properties: Use characteristics, like horizons (particularly upper horizons) for differentiation, base status, temperature, moisture regimes and diagnostic horizons (e.g., plinthite, fragipan).

Properties: Differentiating criteria include texture, mineralogy, temperature regimes and thicknesses of root penetration zones. This is important for crops and engineering purposes (roots, water retention, aeration).

Concept: Collection of soil individuals sharing similar characteristics, mainly differences in horizon expressions (e.g., thickness, color) within a certain range of variability.

Factors: Based on limitations like risk of runoff/erosion, wetness, root development, degree of erosion and soil type.
Capability Classifications: nine classes (A to Y) categorise land suitability for different uses.

Evaluation: Correlation of data (crop yields, soil characteristics, climate, management) to evaluated land productivity.
Formula: Rating index (SPI) = P - CM - CL, where P is performance index, CM is corrective measures index and CL is continuing limitation index.

Principle: Transfer soil management techniques if soil properties are similar in different areas. Critical properties are texture, mineralogy, moisture/temperature regimes, and factors affecting plant growth. Soil Family classification is a suitable basis for technology transfer.