The Soils of Elgin County - Agriculture and Agri-Food Canada

HOW THE SOILS WERE MAPPED AND CLASSIFIEDSoil MappingThe resurvey of the soils of Elgin County wasundertaken in a series of stages . The first stageconsisted of a sampling program in which thesoils were described and sampled according to soiltypes and their spatial distribution as indicated onthe old soil map. Data from this samplingprogram, and information gathered from existingresource publications such as geological reports,was used to build the soil legend which appearson the border of the soil maps .The second stage of the resurvey involved thedetermination of tentative soil boundaries throughstereoscopic examination of aerial photographs,and field checking of the soils occurring withinthose boundaries. At each field check, standardsoil classification guidelines outlined in '"TheCanadian System of Soil Classification" (11) and"The Canada Soil Information System (CanSIS) -Manual for describing soils in the field" (12) wereapplied . The Ontario Institute of Pedologypublication "field manual for describing soils" (13)was also used at field checks . These publicationsdefined the limits employed in this survey forslope, texture, and drainage classes . Additionalsampling was undertaken at some field checks toexpand the soil database.Field checking was mainly carried out alongpublic roads which generally provided easyaccess. Site inspections were carried out on aregular basis, especially in areas wherestereoscopic interpretations suggested major soil orlandscape differences were present. At each site,vertical soil sections were examined through theuse of a probe, auger, or shovel. Soil texture anddrainage were assessed at each site, as well assurface slope . Most examinations were made to adepth of about one metre below the surface.The final stage of the resurvey involved thecompilation of soil maps from informationcollected in the field. The information wasrecorded on site cards and on aerial photographs,and was used to compile a series of maps whichwere first published in preliminary form (2,3,4).Revisions made to those maps resulted in the finalmaps which accompany this report. Digitizationof the final maps was then undertaken to providehectarages for each soil type, and to create adigital data base from which future interpretivemaps could be produced .Survey Intensity Level and MapReliabilityThe scale of the maps and the amount ofprecision or the intensity level with which thesoils would be described and mapped were bothdetermined before the resurvey began. A"SurveyIntensity Level" was therefore assigned to theproject. The survey intensity level relates to thenumber of field checks per unit area mapped, thenumber of delineations on the map having at leastone inspection, the methodology used to establishsoil boundaries, and theminimum size area whichthe map can portray.Five survey intensity levels have been definedin the publication " A soil mapping system forCanada : Revised" (14). Survey Intensity Level 1 isthe highest intensity, having the most detailedprocedures and the greatest level of precision.Large scale surveys such as those at a scale of1:10,000 would have this intensity level . SurveyIntensity Level 5 has the lowest intensity, the leastdetailed procedures, and the lowest level ofprecision. An example would be small scalesurveys such as those at a scale of 1:250,000, whichpresent generalized information.The Elgin County resurvey was carried out atSurvey Intensity Level 3, which is an intermediatelevel. The map publication scale of 1:50,000 isconsidered appropriate for that intensity level, andat least one site inspection was carried out in mostdelineations shown on the maps (14) . In areaswhere the soil landscape was highly variable andtherefore less predictable, more site inspectionswere carried out .Since the minimum size of delineation whichcan be shown on the soil maps is 0.5 cm2, orapproximately 12 ha (30 acres) on the ground (14),the maps provide information at a level of detailwhich is most suited for making general landassessments and management decisions . Theirmost appropriate use, therefore, is for planning atthe county, township or watershed level, or forbroad targeting of soil related agriculturalprograms. For land assessments or decisionsrelated to small areas, additional on-siteexaminations of soil characteristics arerecommended. The soil identification keysprovided in Appendix 2 can be used to identifythe soils at site examinations .