Suo - Mires and peat vol. 54 no. 4 | 2003
Pitääkö kaikkein happamimmat sulfaattimaat poistaa viljelystä?
English title: Should the cultivation of the most acidic sulphate soils be stopped?
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Tekijä
Estimates of the area of cultivated acid sulphate soils in Finland range from 50,000 ha to 336,000 ha. In these soils, sulfides are oxidized to sulphuric acid upon aeration, which is promoted by drainage. Agricultural use of these soils requires abundant liming. Acidic drainage waters impact the aquatic life negatively. Early research concentrated on the agricultural utilization of acid sulphate soils while more recently environmental aspects have been emphasized. Controlled drainage, aiming at a high water table, is considered an option for the management of acidity. Owing to evapotranspiration, however, sulfidic layers may be exposed to oxidation every summer in spite of controlled drainage. Successful submerging of sulfidic layers may require pumping of water to the field from outside sources. Abandoning the most acidic sulphate soils and stop draining them would prevent further oxidation of sulfides. This is a sensitive issue, because the farmland is private property. Moreover, it is not exactly known where the most acidic sulphate soils are located and how their abandonment would impact the quality of water in recipient rivers.
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Yli-Halla,
MTT Agrifood Research Finland, Environmental research, FIN-31600 Jokioinen, Finland
Sähköposti:
ei.tietoa@nn.oo
Elämästä humusta - humuksesta elämää.
English title: Humus - product and source of life.
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Despite agreement that organic matter is an essential soil component, terminological
confusion may result in inexact concepts of its role in controlling the chemical, physical
and biological processes. Humus, which is synthesized primarily in humification
process by microbes, is structurally very complex and resistant to degradation. It is
produced from non-humus material: litter, a whole series of decomposition products,
and identifiable constituents. Classifying soil organic matter into humus and non-humus
materials permits the systematization of reactions involving organic matter. Microbial
degradation of non-humus material releases plant nutrients and produces
polysaccharides that stabilize soil aggregates, thus improving conditions for root growth.
Antibiotics, vitamins and other active compounds affecting the biotic system can end
up into soil as byproducts of the microbial metabolism. Only a very small portion of
non-humus material is used as raw material for humus, whose importance is based on
physico-chemical properties. Through its high water holding capacity, humus can physically
control the mobility of compounds. Diverse functional groups participate in various
types of chemical reactions (ion exchange, complex formation, dissolution, physical
sorption of non-polar organic chemicals, etc). Similarly as in soil, humus acts as a
buffer in water bodies. However, in contrast to soil, in waters photochemical reactions
can enhance its degradation, thus leading to nutrient loadings and oxygen budget problems.
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Hartikainen,
Department of Applied Chemistry and Microbiology, Box 27, 00014 University of Helsinkin, Finland
Sähköposti:
ei.tietoa@nn.oo
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