Saturday, 15 July 2006

Indicators of Soil Degradation Processes on a Chernozem Field in Hungary.

Anita Gal1, Tamas Szegi1, Barbara Simon1, Balazs Szeder1, Erika Micheli1, Etelka Tombacz2, Adam Zsolnay3, and Junko Akagi3. (1) Szent Istvan Univ, Soil Science and Agrochemistry Dept, Pater K. u. 1., Godollo, 2103, Hungary, (2) Univ of Szeged, Dept of Colloid Chemistry, Aradi Vt. 1., Szeged, 6720, Hungary, (3) GSF Institut für Bodenökologie, Ingolstadter Landstrasse 1, Neuherberg, 85764, Germany

Soil degradation is a severe problem all over the world. Finding indicators and giving predictions of soil degradation is an important task to prevent loss of our most important natural, non-renewable resource. The study area is located in Hungary, in the Carpathian basin. Most of the agricultural soils in Hungary developed on calcareous loess, which is a favorable parent material for fertile soil formation. Chernozems have been considered very good soils in their natural conditions, but most of these loess derived soils have been cultivated for several centuries. Unfortunately, almost the entire area of Chernozems in the country has experienced erosion and/or structural degradation mainly due to inappropriate land use practice. Monitoring soil quality is an important, but recent, activity. The objective of the research was to find early biological and physical indicators for soil degradation on a Chernozem soil. The study area is located on the Szent István University Experimental Farm, in Northern Hungary. Four soil profiles were examined in details on a topographic catena, representing different levels of erosion (no, low, high erosion and accumulation profile) and other types of soil degradation (structural and biological). The following laboratory analyses were carried out: •general laboratory analyses (total organic carbon – TOC %, soil organic matter – OM %, dissolved organic carbon – DOC, cation exchange capacity – CEC, pH, size distribution, CaCO3 content, base saturation – BS% and bulk density – BD determination), •detailed characterization of organic matter (humic acid and fulvic acid extraction, fractionation and determination of the E4/E6 ratio) •microaggregate stability measurement by rheology (Vane method), •analyses for biological parameters (ratio of different functional groups of microorganisms (bacteria, fungi) and density of earthworms and springtails) and •enzimatic characterization (dehydrogenase, urease, phosphatase and ß-glucosidase activity). Based on the general laboratory analyses we concluded that the organic matter content and quality declined with increasing degree of erosion. At the lowest profile position (accumulation profile) structural degradation of the translocated organic matter was shown. Consequences of these drastic changes in the organic matter status of the soil could be well defined by measuring changes in the structural stability and biological parameters. Rheology gives good indication of microaggregate stability through examining the strength and stability of the physical network and the composition of the particles. These soil properties have strong, well-defined connection with tolerating cultivation and capability for withstand erosion. According to our rheological measurement the bonding strength between soil particles in microaggregates declined, thus structural degradation and susceptibility for erosion could be well defined. The physical parameters compared to the biological parameters are more resistant and change slower in soils, thus the use of biological parameters for early indication of degradation could be more appropriate. Along the sampling sites we have found that with increasing level of physical degradation and decline in organic matter content the investigated biological and enzymatic parameters followed a tendency toward deterioration. (Acknowledgement: INDEX Nr. GOCE-CT-2003-505450)

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