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Custom Soil Resource Report <br /> Aggregation Method: Dominant Condition <br /> Aggregation is the process by which a set of component attribute values is reduced <br /> to a single value that represents the map unit as a whole. <br /> A map unit is typically composed of one or more "components". A component is <br /> either some type of soil or some nonsoil entity, e.g., rock outcrop. For the attribute <br /> being aggregated, the first step of the aggregation process is to derive one attribute <br /> value for each of a map unit's components. From this set of component attributes, <br /> the next step of the aggregation process derives a single value that represents the <br /> map unit as a whole. Once a single value for each map unit is derived, a thematic <br /> map for soil map units can be rendered. Aggregation must be done because, on <br /> any soil map, map units are delineated but components are not. <br /> For each of a map unit's components, a corresponding percent composition is <br /> recorded. A percent composition of 60 indicates that the corresponding component <br /> typically makes up approximately 60% of the map unit. Percent composition is a <br /> critical factor in some, but not all, aggregation methods. <br /> The aggregation method "Dominant Condition" first groups like attribute values for <br /> the components in a map unit. For each group, percent composition is set to the <br /> sum of the percent composition of all components participating in that group. These <br /> groups now represent "conditions" rather than components. The attribute value <br /> associated with the group with the highest cumulative percent composition is <br /> returned. If more than one group shares the highest cumulative percent <br /> composition, the corresponding "tie-break" rule determines which value should be <br /> returned. The "tie-break" rule indicates whether the lower or higher group value <br /> should be returned in the case of a percent composition tie. The result returned by <br /> this aggregation method represents the dominant condition throughout the map unit <br /> only when no tie has occurred. <br /> Component Percent Cutoff.-None Specified <br /> Components whose percent composition is below the cutoff value will not be <br /> considered. If no cutoff value is specified, all components in the database will be <br /> considered. The data for some contrasting soils of minor extent may not be in the <br /> database, and therefore are not considered. <br /> Tie-break Rule: Lower <br /> The tie-break rule indicates which value should be selected from a set of multiple <br /> candidate values, or which value should be selected in the event of a percent <br /> composition tie. <br /> Farmland Classification (Two Rivers Ranch Area Soils) <br /> Farmland classification identifies map units as prime farmland, farmland of <br /> statewide importance, farmland of local importance, or unique farmland. It identifies <br /> the location and extent of the soils that are best suited to food, feed, fiber, forage, <br /> and oilseed crops. NRCS policy and procedures on prime and unique farmlands are <br /> published in the "Federal Register," Vol. 43, No. 21, January 31, 1978. <br /> 42 <br />