SOIL DEVELOPMENT IN LOESS IN THE SOUTHERN MISSISSIPPI VALLEY

Publisher Website
Google Scholar
Abstract
Recent field studies indicate that soils formed in similar-aged parent material, Peorian loess, under the more intense climate of the Southern Mississippi Valley have greater amounts of albic materials in subsurface horizons than in soils of the middle Mississippi Valley. The albic material is formed by a hydromorphic soil-forming process called ferrolysis. It consists in destruction of clay caused by cation exchange reactions involving iron in repetitive reduction-oxidation cycles taking place under conditions of alternative wetness and dryness. The process is accelerated by greater amounts of leachable water. Studies of topo-sequence relationships suggest that soils in the lower positions receive additional waters and have lost the upper argillic horizons common in the convex-shaped soils. This horizon has been replaced by albic materials; in addition, albic materials tongue into horizons below. The amount of albic materials and destruction of argillic horizons diminish on the sloping soils as rate of water runoff increases. The comparison of soils formed in loess of different age, under similar climate and vegetation, indicates that the fragipans common to soils in the younger loess are destroyed by excessive tonguing of albic materials in the older soils. Glossudalfs and Glossaqualfs are the common soils of the older pre-Peorian loess. The genesis of the albic horizon is reflected in recent modifications of “Soil Taxonomy” (Soil Survey, 1972). Haplic and Fragic subgroups of Glossudalfs, and Glossic and Glossaquic subgroups of Fragiudalfs resulted from these recent studies. Recent field studies indicate that soils formed in similar-aged parent material, Peorian loess, under the more intense climate of the Southern Mississippi Valley have greater amounts of albic materials in subsurface horizons than in soils of the middle Mississippi Valley. The albic material is formed by a hydromorphic soil-forming process called ferrolysis. It consists in destruction of clay caused by cation exchange reactions involving iron in repetitive reduction-oxidation cycles taking place under conditions of alternative wetness and dryness. The process is accelerated by greater amounts of leachable water. Studies of topo-sequence relationships suggest that soils in the lower positions receive additional waters and have lost the upper argillic horizons common in the convex-shaped soils. This horizon has been replaced by albic materials; in addition, albic materials tongue into horizons below. The amount of albic materials and destruction of argillic horizons diminish on the sloping soils as rate of water runoff increases. The comparison of soils formed in loess of different age, under similar climate and vegetation, indicates that the fragipans common to soils in the younger loess are destroyed by excessive tonguing of albic materials in the older soils. Glossudalfs and Glossaqualfs are the common soils of the older pre-Peorian loess. The genesis of the albic horizon is reflected in recent modifications of “Soil Taxonomy” (Soil Survey, 1972). Haplic and Fragic subgroups of Glossudalfs, and Glossic and Glossaquic subgroups of Fragiudalfs resulted from these recent studies. © Williams & Wilkins 1973. All Rights Reserved.

This publication has 0 references indexed in Scilit: