SOIL Survey Provides Data for Classifying Land; Planning Uses
Various local and State governments, faced with problems of tax delinquency resulting from the inability of farmers to earn an income from soils that are too unroductive or remote from markets, are demanding some program for and use which will enable the citizens of the distressed communities and counties to support their schools and roads.
In one form or another such programs are at present under way in New York, Wisconsin, North Dakota, Michigan, and Washington. The various measures put into effect by these governments for planning land use and for the conservation of resources immediately call for an accurate inventory of the relative productive values of the different soils of areas concerned. Obviously a classification of the land is the first essential step in attempting to meet this problem. The growth of plants, whether for crops, grazing, or forestry, is so intimately bound up with the nature of the soil type that the physical quality of the land ultimately determines, more than any other factor, the possibility for success of any agricultural enter rise. In the case of the cropping-use group especially, the units of operation—farms and ranches—are small and individual. Physical information about the land must be sufficiently detailed in its geographic expression on maps to indicate clearly the nature of the land on each unit. As a further requirement it was necessary to have an approximate idea of the total extent of the various soil types, capable of use for the various types of enterprise.Fortunately about half the nonmountainous part of the United States had been covered by the soil survey and the data were available for the necessary land classification. A part is covered by reconnaissance soil surveys made on a scale of about 2 to 6 miles to the inch and showing the general distribution of the principal soil types. The greater portion is covered by detailed surveys on a scale of 1 mile to the inch and showing accurately the distribution of the soil types and other physical features of the land in close detail. Detailed reconnaissance surveys cover projects having nonmountainous areas requiring detailed work and mountainous areas in which only general features need be shown.
The soil map is accompanied by a report describing the various soil types and explaining their use. The general conditions of climate, vegetation, physiography, geology, and drainage are described as well as the detailed condition for each type. Agricultural practices are discussed, giving statistics as to crops grown, yields obtained, market facilities, and similar material having a bearing upon the use of the land.
Each soil type has quite definite, determinable possibilities for the growth of crops, grasses, or forests. Through the long accumulation of data and experience by research workers and farmers on soil types, much definite information is now available. The Division of Soil Survey has prepared definite ratings of natural productivity for each soil type for the various crops grown in the majority of the areas. These ratings were made in cooperation with the State experiment stations and represent the result of accumulated experience on each soil type. These data have been compiled for the United States as a whole and may be summarized in 5 classes from 1, the best, to 5, the poorest, according to natural productivity as shown in table 12.
| Class | Area surveyed Acres | Percentage |
| 1 | 100,752,633 | 5 |
| 2 | 210,707,665 | 11 |
| 3 | 346,172,420 | 18 |
| 4 | 362,025,639 | 19 |
| 5 | 881,931,310 | 47 |
Total | 1,901,589,667 | 100 |
The Division of Soil Survey has completed a cooperative project with the North Dakota Agricultural Experiment Station for a detailed land classification in McKenzie County, N. Dak. Billings County of the same State will be completed early in 1935, and Morton County somewhat later. Other counties are being taken up as rapidly as possible.
This work was organized at the request of the local officials in the counties for the special purpose of making assessments for taxes on land according to its producing capacity.- Although such a classification of lands on a uniform basis for appraisal rests primarily on the nature of the soil, other factors necessarily are considered. The degree of slope and of stoniness are carefully noted, as well as the nature of the grass cover, forest growth in the stream valleys, presence of alkali, accessibility to markets, and similar factors which influence the production of farms and ranches.
The procedure developed for this work consists of four principal steps:
(1) The soils and other physical features of the land are mapped
in detail on a scale of 2 inches equals 1 mile, in classes defined according to their practical significance.
(2) The natural productivity of each important combination of soil,
slope, and stoniness, is determined by studies of the actual use of these
lands, both for grazing and for crop production. Thus each land type
is given a numerical rating in terms of its percentage of the ideal, or
best-producing land of the county, both as cropping land and as grazing land.
(3) The use group (cropping or grazing) of each tract of land is
determined largely on the basis of the amount of the various land
types and on accessibility. Land naturally adapted to crops is rated
as cropping land unless the area is too small or too far distant from
other cropping land for economic farming. In this area, land unsuited
for cropping is rated according to its productive capacity.
(4) According to the relative amounts and productive capacity of each of the land types and the social unit of land (farm, ranch, or other
holding) each tract of land is given a composite rating in terms of ideal
land, as 100 percent. These values are reduced conformably to a uniform schedule according to their accessibility to markets, as determined by the distance and the type of road. Those grazing lands
lacking natural sources of water take a further reduction. As the lands
in North Dakota were surveyed and sectionalized by the Government Land Office, the land is listed on the tax roll by forties according to the
survey. The results of the land classification are also given on the
basis of the 40-acre unit. Thus each forty is given a rating between
0 and 100 percent according to its productive capacity, in an economic
sense in relation to the best, or ideal land of the county.
With such a classification in hand, it only remains for the local officials to determine the assessed valuation of ideal land, and all other land takes its appraisal according to its productive capacity. County officials have encouraged the development of this procedure with the thought of obtaining a more equitable and practical distribution of local taxes on farm land. At the same time the data obtained in the course of the classification are those required for any planning of land use. These same appraisal values are being used in the acquisition of lands for grazing districts and public parks.
In order to furnish a basis for planning agricultural development in the Tennessee Valley, the Division of Soil Survey is cooperating with the Tennessee Agricultural Experiment Station and the Tennessee Valley Authority in making soil surveys for that area. Detailed mapping of the soil types and other physical features of the land is followed by a crop survey in order to establish the yields, crops, and kinds of management most characteristic of each of the widely different soil types.
A somewhat similar type of survey is being conducted in cooperation with the Washington Agricultural Experiment Station at the request of the local residents, in order that a more practical use of lands may be developed and the local expenditures, especially for schools and roads, brought into harmony with the potential producing power of the area.