Saturday, 15 July 2006

Transformation of Humus Substances of Locally Hydromorphic Chernozems of the South of Russia.

Svetlana A. Tischenko and Olga S. Bezuglova. Rostov State Univ, B. Sadovaya., 105, Rostov-on-Don, 344006, Russia

The modern development of agricultural production results in basic changes of the soil cover. During the last decades, soils in a steppe zone are characterized by development of some degradation processes. A special place among the processes are expansion of areas of soils that are periodically saturated with water. Increasing areas of locally hydromorphic soils are investigated as changes of regimes and properties of chernozems which are exposed to intensive humidifying. This process has affected a lot of territories in the south of Russia, Moldova, and Ukraine. Steppe zones are characterized by insufficient humidity. Expansion of locally hydromorphic soils replaces the initial automorphic soils with hydromorphic soils which has a low level of fertility. Agricultural plants on such soils do not thrive and often die. The local water saturation of the soil profile influences the formation of gleic or solonetzic soils (such soils were named mochars or mocharic soils). Transformation occurs quickly and results in change of the soil cover structure. It is necessary to note that water saturation is distributed in soils, outside of irrigating systems. It is obvious, that humidity results in developing adverse physical and chemical soil properties. Among other changes, humus conditions such soils has also observed. Development of reductive processes, and existance of alternate vegetation is the result of seasonal waterlogging. This provides an increase of the content of the common carbon in humus profile. Many soils pass from a powerful to a super powerful category,thanks to the fact that humic substances can migrate down in the soil profile. As a whole, changes of humuc substances are characterized by certain tendencies. The total content of humic acids has decreased. The sum of the fulvic acids has increased. The share of nonhydrolized part of humus (humin) has decreased. As consequence of these actions, ,humus type has changed. The structure of fractions of humus acids and fulvic acids have changed too. The share of mobile fractions increases. The tendency to accumulate the fractions which are strongly connected to clay minerals is observed. But in each case primary humus state of chernozems will determine a degree of change of soil humus substances during of the humidifying because of properties hydromorphic soils inherit from chernozems. The big role will play other factors, for example chemical content of subsoil waters and duration of the waterlogged period. The received data once again confirm that fact, that similar soils demand the individual complex approach in studying the reasons of their occurrence, and their physical and chemical properties. As a whole, it can be said that development of the local humidity results in change of the humus state of chernozems on a way of its degradation.

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