Graduate Thesis Or Dissertation
 

A model for rating agricultural suitability of land parcels in western Oregon

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/d217qt94g

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  • A model was developed that allows potential users to identify the agricultural suitability of parcels of land in western Oregon. Literature was reviewed regarding five possible benefits to be derived from public policies designed to preserve productive agricultural land. They are (1) the provision of sufficient cropland to supply the food needs of an expanding national and world population; (2) the maintenance of healthy local economies in predominantly agricultural areas; (3) the increased efficiency that results from more orderly urban development; (4) the reduction of resource misallocations resulting fromthe conversion of the better agricultural lands to other uses; (5) the provision of open space in rapidly urbanizing areas. Systems currently being used to identify productive agricultural land were also reviewed. Among these were the land capability classification system, the "prime" and "unique" farmlands criteria, and various numerical indices such as the corn suitability rating. A comprehensive compilation was made of all factors having potentially significant effects on agricultural land use. Similar factors were grouped together and a model was developed incorporating the most important of these factors. Specific criteria were developed for evaluating the effects of the factors. The workability of the model was determined by applying it in several test areas and through numerous consultations. The model itself was developed in the form of a branching flow chart. After an initial question regarding commitment to other uses has been answered, the procedure involves the determination of two separate scores, one for soil productivity that ranges from 0-52 points and one for compatibility that ranges from 0- 48 points. The overall rating of agricultural suitability ranges from 0-100 points and is obtained by adding the two separate scores. Information needed to calculate the two scores is readily available. The determination of the soil productivity score requires use of crop yield data as well as irrigation and drainage information for soil map units. The determination of the compatibility score requires information about surrounding land uses and the location of the nearest urban growth boundary. To validate the model 43 parcels of land in six counties in western Oregon (Benton, Clackamas, Jackson, Lane, Marion and Tillamook) were selected as representative of six predetermined situations regarding soil productivity and extent of urban growth pressure. These situations were: (1) highly productive soils with little growth pressure; (2) highly productive soils with heavy growth pressure; (3) moderately productive soils with little growth pressure; (4) moderately productive soils with heavy growth pressure; (5) soils with relatively low productivity and little growth pressure; (6) soils with relatively low productivity and heavy growth pressure. The t test using pooled variances (Sp²) was used to determine whether differences between the means of the six situations were significant. The resulting analysis showed that when applying the model, those parcels with highly productive soils and little growth pressure had significantly higher total scores than all other parcels. Likewise, the parcels with soils of relatively low productivity and heavy growth pressure had the lowest scores. The other parcels fell somewhere in between. The model has several potential applications in Oregon. It can be used as a tool in evaluating the effects of changes in agricultural management, in evaluating the effects of land use decisions on surrounding agricultural lands, or in evaluating proposals for lot splits. It could also be used as part of the general long-range planning process. Other applications may be discovered by potential users as the need arises.
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