Saturday, 15 July 2006

Transformation Processes of Soil Formation and Fertility of Chernozems of the Steppe Zone of the Altai Region.

Gennady G. Morkovkin and Nina B. Maksimova. Altai State Agricultural Univ, Krasnoarmeiskiy Prospekt, 98, Barnaul, Russia

Among numerous human impacts on the environment, the most cardinal is plowing up virgin lands. When soils are made arable, stability of the agricultural landscape is lost. And it is stability of soils to external influences that is an important component of ecosystems' stability and the biosphere on the whole. The soils of the plain territories of the Altai Region, involved in the research, are noted for broad diversity. The top-soil is represented by all chernozem subtypes and accompanying soils of semihydromorphous and hydromorphous series. The geographic position of the Altai Region in the heart of the continent provides uniform enough inflow of radiant energy. The climate of the Region is characterized by significant continentality and instability of weather classes on seasons of year. The relief of the chernozems' zone is plain. Soil formation rocks are loess-like carbonate loams. Prior to plowing the chernozems' zone was characterized by development of abundant motley grass-fescue-feather grass vegetation with cespitose cereals (Stipa capillata, St. Rubens, Festuca sulcata), with individual insertion of rhizophorous cereals (Bromus inermis, Calamagrostis epigeios) and various motley grass (Peucedanum Morisonii, Veronika spicata, V. incana, Fragaria veridis, Galium verum, Galatella fastigiata, Medicado romanica, Silene multiflora, Pulsatilla patens seseli, Ledebourii, Artemisia glauka, Alatifolia, etc.). Chernozems are the most fertile soils representing the main available arable land of the Altai Region. At present, the process of chernozem formation in the steppe zone of the Altai Region is exposed to transformation. Constant deficiency of organic matter in the most of agrocenosis reduces humus formation. Decrease in chernozems' fertility is observed, caused by intensive anthropogenic load; ability to self-regulation and maintenance of the basic components of soil fertility at stable level is lost. Agricultural use of land resources without proper top-soil protection measures, without balanced proportion of arable lands within agricultural lands results in erosive processes development, and consequently, in change of soil morphological structure and physical destruction of humus horizons. Degradation processes developing in chernozems are of progressive character, and their development can result not only in catastrophic drop of soil fertility, but also in loss of this particular soil type in its modern classification comprehension. Change of humus horizon capacity in most cases corresponds to the 1st degradation degree; losses of soil mass correspond to the 1st and 2nd degradation degrees. The basic process of chernozem formation, i.e., humus buildup, has undergone essential changes. For 100 years of agricultural use, the soils lost more than half of humus content, loss rate is particularly high at present. Annual average decrease in humus content before 1967 was 0.016% in leached chernozems, 0.038% in common chernozems; after 1967 the drop in humus content was 0.034 and 0.044% yearly in leached and common chernozems accordingly. In farming there developed steady negative balance of basic nutrients, it is particularly high in nitrogen and potassium. The organic matter balance is also negative. It is reduced by straw application into soil. By application 50% of straw and all manure from animal farming it is possible to create self-supporting balance of organic matter. Theoretical basis of proposals on protection and reproduction of soil fertility is to stimulate in soils of different agrocenosis development of turf (chernozem) process of soil formation. To implement that, it is necessary in steppe zone of the Altai Region to take note of the following:(1) Creation self-supporting balances of organic matter and basic nutrients in crop rotations. When planning the structure of sown areas and crop rotations, it is necessary to consider not only their productivity, but also balances of humus and nutrients as well as estimates of organic and mineral fertilizers rates to reproduce soil fertility; (2) When erosion- and deflation-unsound, weakly eroded and deflated soils are used in farming, it is necessary to take all appropriate soil-protective measures; (3) Optimization of agricultural lands' proportions. Exclusion from arable lands strongly degraded and polluted soils.

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