COMET-Farm utilizes SSURGO Soil Data for all soil related calculations. USDA-NRCS defines a map unit as "a delineation on a soil map represents an area dominated by one or more major kinds of soil or miscellaneous areas. A map unit is identified and named according to the taxonomic classification of the dominant soils. Within a taxonomic class there are precisely defined limits for the properties of the soils. On the landscape, however, the soils are natural phenomena, and they have the characteristic variability of all natural phenomena. Thus, the range of some observed properties may extend beyond the limits defined for a taxonomic class."
You can view the map units across your defined parcels by selecting the "soils" button in the top right corning of the map on the cropland, pasture, range, orchard/vineyard accounting activity. This feature is not available via the API.
COMET-Farm will run all of the methods and models (DayCent and those defined in the USDA Blue Book document) on each map unit within a defined parcel and then provided a weighted average of the estimates in the report.