Regions

Soil Management in Regions

Carleton P. Barnes.

To discuss more easily soil-management problems and opportunities presented by the different conditions found in the United States, we have divided the country into 16 regions.

Each of the regions has a combination of climate, soils, and agriculture that tends to give it soil-management problems different from the others.

Few countries have such a great diversity of soils and climates as ours. Our farming is carried on in subtropical climates, where frost seldom occurs, and in areas where frost occurs practically every month of the year.

Several thousand different kinds of soil have been found in our nationwide soil survey. Not all of them are greatly different from one another, but several hundred are unique and must be managed differently to be fully productive.

If all this diversity occurred in random fashion, as though some giant had strewn the different soils and climates around, there would be little point in using regions in discussing soil-management problems and practices. But our soils and climates follow definite regional patterns, each region having within it a distinct pattern of soils and climates. The climates of our Pacific coast differ from those of our Atlantic coast, and each is different from those of the interior of the country. These differences result from latitude, elevation, and the worldwide movement of airmasses across the continent.

Soils likewise have regional patterns. They result from the climate under which the soils have developed rather than from the geologic material from which they came.

There also are local differences in soils which are due to differences in parent rock, topography, and drainage. One could not, however hard he tries, find a soil in North Dakota just like one in Florida, or one in Delaware just like one in Nevada. This regional arrangement of climates and soils and therefore of crops makes it convenient to divide our country into regions to discuss soil management.

This is not to say that soils or climate are uniform within a region. Every farmer knows that soils may differ within a distance of a few feet. These are the local differences in soils due to geology, slope, or drainage. The different parts of a farm and even parts of a field may need different treatment. But the two or three kinds of soil on a farm in the Central Valley of California will not be the same as the three or four on a farm in Iowa, or Alabama, or New York. And in many ways they will be like soils elsewhere in the Central Valley even elsewhere in California.

Each of the 16 regions, therefore, has within it many different soils and local differences in climate. But the combination of conditions within a region generally is different from the combination of conditions in other regions.

We must realize that in passing from one region to another we often find a gradual rather than an abrupt change from the conditions of one to those of the other. But when we show the regions on a map we have to draw a line between them, implying thereby that on one side of the line we find one thing and on the other side we find something quite different.

Climate is one of the main characteristics that distinguish one region from another, but it is not the only one. Climate sets limits on the kinds of crops that are advantageously grown and that largely determine the kinds of soil-management systems and problems. Climate determines the soil moisture regime that is to be expected, and a large part of soil management is aimed at providing crops with the right amounts of moisture.

Because of the importance of climate, for example, we treat the North Pacific coastal valleys as a distinct region. No other part of the country is quite like it. We separate the winter wheat region of the Great Plains from the spring wheat region, and we separate the regions where cotton is an important crop from those where it is too cold for cotton because of climate, we can say, but actually because of differences in the whole complex of climate, crops, types of farming, and soils that make the problems of soil management different.

The boundaries of the regions are not all determined by climate. Where we have a great region with a soil pattern strongly different from surrounding areas, like the lower Mississippi alluvial valley, or Delta, such a region is marked out for separate discussion even though its climate may not sharply contrast with neighboring regions. A regional boundary has been drawn along the eastern edge of the major Texas Blackland. This is a soil boundary primarily, although it also serves to separate a more humid region to the east from a less humid one to the west. The soil boundary, however, is the sharper and more easily recognizable of the two and therefore was used. Wherever practical, regional boundaries are drawn to coincide with recognizable topographic or soil breaks, even though the principal difference between the adjoining regions may be a climatic one. This procedure has the advantage of putting the whole of a soil or topographic area into one region, instead of splitting it.

On our maps here, the regional boundaries are smoothed that is, a boundary as shown does not try to follow the detailed position of the actual, on-the-ground boundary where, for example, it zigzags around inter-fingering mountains and interspersed narrow valleys. Instead, it strikes a general course approximately separating the two kinds of regions. This practice avoids having boundary delineation more detailed than is justified by the diverse character of the regions.

Let us see what these regions are like and how they differ.

1. THE NORTH PACIFIC VALLEY REGION is the humid region of cool summers and mild winters west of the Cascade Mountains in Washington and Oregon and the northwestern corner of California. Except for a narrow strip along the California coast, it is our only region where it is cool in summer yet mild in winter. We call it humid because the yearly moisture received is fairly large, but there is a pronounced dry season, usually in July and August. This makes irrigation advantageous in some places, especially where the soils have a low moisture-storing capacity. Actually this region, as shown on our map, contains large areas of rough, mountainous, forested land.

This region differs from region 2 in being much moister and in having much cooler summers than all of region 2 except a narrow strip along the coast. It differs from region 4 in being moister and milder in winter.

2. THE DRY MILD-WINTER REGION is our only region with mild winters and low moisture supply. The mountains of the California coastal ranges are exceptions to the generally dry climate, but they cannot be placed conveniently in any other region.

The part of the region in southern Texas differs from the rest in that most of its rainfall is in spring and summer instead of in winter.

The region includes the lower, western foothills of the Sierra Nevada but not the forested higher parts. Most of the region is hot in summer. Only the mountains and a narrow strip along the California coast are cool. This is the region of all-irrigated production of citrus and other subtropical crops and of long-season, intensive, irrigated agriculture.

This region differs from region 4 primarily in its warmer winters and longer frost-free season. On the whole, it also is hotter in summer.

3. THE PACIFIC NORTHWEST WHEAT REGION is the largest dryland farming region west of the Great Plains.

It differs from the dryland farming regions of the Great Plains in that most of the moisture comes in winter.

It differs from region 4, which surrounds it, in having mainly fertile soils that have good moisture-supplying characteristics. They were developed under grass from wind-blown material.

4. THE GRAZING-IRRIGATED REGION has three principal components: Arid grazing land; mountain forest land, most of it also used as range; and irrigated cropland. There is also some dry-farmed cropland. All of these elements occur intermingled with one another in large and small bodies throughout the region. Each has distinctly different sets of soil-management problems.

This region differs from regions 5, 6, and 7, which adjoin it on the east, mainly in its more arid character (except for its mountains), which makes it mostly too dry for nonirrigated farming. It has many forested mountains.

5. THE NORTHERN GREAT PLAINS includes the northern and colder part of the Great Plains, a region of rather low and irregular rainfall, in which special practices to conserve soil moisture usually are needed. Winters in the Northern Plains generally are too cold for fall-sown wheat, and spring wheat is the main crop. Large areas of this region have such steep, broken topography or soils with such poor moisture-supplying capacity that they are used mainly for grazing. In the region are a number of isolated, forested mountain ranges, like the Black Hills.

The large Nebraska Sandhill area has also been included, not because it is much like the other parts of the region, but because there seemed to be no better place to put it. If we were dividing the country into 40 or 50 regions instead of only 16, the Nebraska Sandhills would certainly be a region by itself. It is a great area of deep, sandy soils and dunelike topography, used largely for grazing.

The Northern Plains region differs from region 6 in its lower winter temperatures and shorter frost-free season and from regions 9 and 10, which adjoin it on the east, in its less humid climate.

6. THE WINTER WHEAT AND GRAZING REGION, a part of the Great Plains, is intermediate in winter temperature between region 5 (on the north) and region 7 (on the south). Its climate permits growing winter wheat, which is its main farm enterprise. As in other parts of the Great Plains, the moisture supply here is rather low, and the amount of precipitation in a particular year is unpredictable.

The bluestem grazing area of eastern Kansas the Flint Hills is included.

Region 6 differs from region 7, which adjoins it on the south, in its lower winter temperatures and shorter frost-free season. The boundary between them approximates the northern limit of cotton production. Region 6 is less humid than regions 9 and 11, which adjoin it on the east. Because of this drier climate, sorghum, rather than corn, is the main feed crop.