Cover Image
close this book Grazing and rangeland development for livestock production
close this folder Management of rangelands and other grazing lands of the tropics and subtropics for support of livestock production. Technical Series Bulletin No. 23
close this folder II. Inventory of the natural resources base of permanent grasslands.
close this folder 4. World soil grouping for forage production.
View the document a. Tropical soils.
View the document b. Major soil groups.
View the document c. Soil deficiencies and plant growth.
View the document d. Dependence of plants on soils.
View the document e. Laterites and laterite soils.

b. Major soil groups.

The seeming endless diversity of tropical soils can be resolved into major groupings on the basis of their predominant characteristics. The following classification is useful, which also are shown in Figure 6.

Great Soil Groups of the Tropics and Subtropics*


Total land area in millions of hectares

1. Dark Grey and Black Clay Soils(inclusions of chernozems, red dish chestnut soils, and hydromorphic soils)


2. Sierozones, Desert and Red Desert Soils (inclusions of lithosols, regosols, and saline soils)


3. Latosols, Red-Yellow Podzolic oils (inclusions of hydromorphic soils, lithosols, and regosols)


4. Red-Yellow Mediterranean Soils(inclusions of terra rosa soils, some mountainous areas, and many areas of rendzina soils)


5 Soils of Mountains and Mountain Valleys (inclusion of many lithosols)


6. Alluvial Soils (Includes innumerable areas in all regions, that are included in other soil groups. These soils have been estimated to support 25% of the world population. Alluvial soils are formed by sediments from flowing waters in river and stream valleys and deltas, and in intermit tent channels of rainfall runoff in watershed basins. These soils lie in the present day flood plains of these waters, or as terraces and benches of earlier geologic periods.)


*Derived from article by C. E. Kellogg and A. C. Orvedal, published in "Advances in Agronomy" Vol. 21, 1969, by Academic Press, New York.

The major soil groups are shown in Figure 6. This map may be useful in connection with the data given in Table 1, which reports a total of 1,582 million hectares of "permanent grasslands" in the tropics and subtropics, in contrast to 626 million hectares of arable lands used for tilled crops and tree crops of various kinds. Comparatively little research has been done on soil management of grazing lands that support livestock, in contrast to the studies on soils for crops. Enough information has been collected, however, on rangelands and other grazing lands to indicate that the potentials for improvement are often very substantial.

Most upland tropical soils that are cropped are low in organic matter, since the high temperatures foster rapid decomposition of roots and other plant parts that account for production of soil humus in temperate zones. Perennial grasses and legumes on tropical and subtropical grasslands make yearly contributions of fresh organic matter within the soil profile and at the soil surface, thus improving soil permeability to rainfall and recycling minerals from plant tops back into the soil profile. However, any characteristic mineral deficiencies of a soil type must be recognized and corrected by suitable treatments to more fully exploit the forage producing potentials of rangelands and other perennial grasslands.

FIGURE 6. Generalized Soils Map of the World

The basic philosophy is that man either adjusts land management practices to the inherent cap abilities of soils as they occur, or he identifies those limiting factors that can be altered by applications of modern technology, and exploits those opportunities that are economically feasible. Man cannot change the climate, but he can make the most effective use of rainfall, temperatures, and humidity that may be expected to occur. Protection of native forage plants is a first requirement, but introduction of superior adapted forage plant species may also be rewarding.