Date of Award:

1976

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Plants, Soils, and Climate

Advisor/Chair:

Alvin R. Southard

Abstract

The purpose of this study was to determine the accuracy of mapping of pachic and cumulic soils in Cache County. The soil maps that were used for this study as the basemap were the Atlas sheets of the published soil survey of Cache County.

Five map units from Mendou, Nebeker, Avon, Hendricks and Winn which include almost 52 percent of the pachic and cumulic soils in the survey area were selected for this study. These five soils cover large areas when compared to other soil series and they are distributed throughout the county. All these map units were recognized as pachic and cumulic in the published soil survey report. The thickness of the epipedon was therefore selected as the principal criterion for determining the accuracy of the map units.

About 400 samples from the major delineations were studied in the field and the necessary data were collected and interpreted statistically in order to find: (1) the accuracy of each map unit, (2) the inclusions, misclassified and not classified pedons and their proportions, and (3) the estimated thickness of the epipedons.

Attempts were made to select the pedons on transects with appropriate interval, depending on landforms and continuity of soils.

Statistical interpretations were conducted by using the chi-square method. The results for each map units are as follows: for Mendon map unit (MeA) 42-56 percent and for Hendricks map unit (HdD) only 30-60 percent of the samples have characteristics required for the named soil in these map units.

These values are less than 75 percent which is the critical value for the map units by definition. It is concluded therefore that with the available data the Mendon and Hendricks series have been mapped incorrectly. For Nebeker map unit (NbE) 77-93 percent and from Avon map unit (ArA) 85-99 percent of the samples have the characteristics required for the named soil in the map units. These values are more than the critical value (75) so it is concluded that with available data the Nebeker and Avon series have been mapped correctly. For Winn map unit (Wn) 54-82 percent of the samples have the required characteristics of this series. The statistical analysis did not reveal strictly whether the pedons are mapped correctly or not and additional samples are required to adequately test the accuracy of the Winn map unit.

It is concluded that in Cache County the influence of different geologic depositions and variations in topography are two major factors responsible for poor accuracy in mapping the Mendon and Hendricks series.

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