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S-map's primary map layer is soil classes, i.e. delineated areas that are labelled with the soil family name. Each soil family is defined as a unique combination of attributes (NZSC classification, parent material, rock type, dominant texture and permeability class). Soil classes are further characterised as siblings according to their depth to rock class, stoniness, land type, drainage, texture (more detailed), functional horizons and miscellaneous variant information. The uncertainty of each of these family and sibling attribute classes is specified. Associated with the soil class layer will be additional map layers of fundamental and derived soil properties. The fundamental soil properties are depth (diggability), depth to slowly permeable layer, rooting depth, rooting barrier, horizon thickness, stoniness, clay and sand content.
They are developed from sample information and expert knowledge. The derived soil layers are each based on a model (or pedo-transfer function). Some models are simple lookup tables that depend only on the soil class. Others combine various soil, land use, vegetation, climate or topographic attributes in a mathematical formula. Derived layers will include available water (mm), macroporosity, water retention, bulk density, total carbon, total nitrogen, phosphorus, calcium, cation exchange capacity, pH, and phosphorus retention |