Zoltán Szalai

Relationship between iron and trace metal fractionation in soils

Abstract Iron compounds significantly affect the behaviour of trace elements in soils. Sequential chemical extractions are widely used to estimate not only the solid phase speciation of chemical elements but to study their mobilisation conditions. In this paper, we present results about the effect of iron fractionation on that of trace metals (Co, Cr, Cu, Ni, Pb and Zn) in representative soils for Hungary. Our aim was to study the effect of pedogenic processes and soil parent material on trace metal association with soil iron phases. Two major soil groups, such as Luvisols and non-Luvisols could be established based on trace metal content, distribution and fractionation in the studied soils. Such differences were found to be primarily due to the differences in the pedogenic processes in the studied soils, whereas soil parent material has not affected these characteristics significantly. We found that Fe phases affect trace metal fractionation and mobilisation as their host in form of both inherited and pedogenic phases. However, pedogenic processes, primarily iron and organic matter accumulation in our case, generally overwrite the effect of inherited iron phases on trace metal accumulation, distribution and fractionation. Among the studied metals, fractionation of Co and Cr were found to be much more affected by that of Fe, followed by Cu, Zn and Ni, whereas Pb could be associated with iron phases only subordinately.

Conservation tillage vs. conventional tillage: long-term effects on yields in continental, sub-humid Central Europe, Hungary

The present study reports novel data concerning Conservation Tillage (CT) in the continental sub-humid climate zone in Central Europe (Hungary), an area which has been mostly neglected in the course of previous CT studies. The results of a 10-year (2003–2013) comparative study of mouldboard ploughing tillage (PT) and CT (no inversion, using a reduced number of tillage operations and leaving min. 30% crop residues on the soil surface) types are reported. Our extensive monitoring system has provided new and detailed information concerning technologies and yields both from the first, transitional period and, over the following years, of adapted technology. Our results suggest that tillage type was a more important factor in the question of yields than either the highly variable climate of the studied years, or the diverse slope conditions of the plots. During the first three years of technological changeover to CT (2003–2006), a decrease of 8.7% was measured, respective to PT. However, the next seven years (2007–2013) brought a 12.7% increase of CT yields. Our study revealed key factors in the initial reduction of crops during the technological change, and may accordingly serve as a guideline for the shortening or avoidance of decline in the transitional period.

The Somogybabod Gully: Hidden Erosion (Piping) in the Somogy Hills

Gully formation is a serious problem in crop production, landscape management and freshwater eutrophication. A recent spectacular example, the Somogybabod gully came into being in the early summer of 2010 after an extremely wet spring. Usually a very rapid process, especially on loess, gully development in this case was supported by improper land use, catchment management and previous piping. Piping and tunnel formation take place invisibly underground. When tunnel roofs collapse, rather deep gullies are exposed within few minutes—as it happened at Somogybabod. Although several active permanent and ephemeral gullies are found in the surroundings, only the Somogybabod gully attracted the attention of scientists because it was initiated under forest cover and, threatening houses, was also highlighted by the media. The aroused public interest could provide an opportunity to face and solve the problem. Instead of runoff mitigation, however, only the filling up of the gully was considered—no long-term solution without the control of surface hydrology and field-scale complex amelioration.

Characterization of Soil Organic Substances by UV-Vis Spectrophotometry in Some Soils of Hungary

UV-Vis spectrometry methods are widely used to characterize soil organic matter, especially humic substances from different extracts of soils. Our aims were to investigate organic characteristics of soils, as part of a project focusing on relationships between solute mineral components and organic matter quality. The study was performed using UV-Vis spectrophotometry on six Hungarian soils. For the characterization of humic substances we used several visible and UV methods. Humic materials were extracted from soils using a variety of extractants. We found that a decrease in pH and an increase in dissolved electrolyte concentration supported coagulation in preferance to dissolution in almost every case. The highest absorbance values was given by extractants which contained sodium-pyrophosphate. In our experience double extraction methods (ENaF/ENaOH according to Hargitai, A talaj szerves anyaganak meghatarozasa es jellemzese. In: Buzas I (ed) Talaj- es agrokemiai vizsgalati modszerkonyv II. Mezőgazdasagi Kiado, Budapest, 1988, E400NaOH+Na4P2O7/E400PBS) and E4/E6 are suitable for analysing humic substances. Comparing these three visible methods there are only slight differences between them. The results do not show strong correlation between visible and UV methods as these techniques analyse different properties of soil humic substances.

Soil Organic Carbon Redistribution by Erosion on Arable Fields

Colloids are thought to move easily, consequently both mineral and organic colloids are overrepresented in runoff and soil loss, which causes selective erosion. Soil loss compound is a function of scale. The enrichment of soil organic carbon (SOC) and of the clay fraction in soil loss was studied at two sites in Hungary. A rainfall simulator was applied to describe selective erosion at micro (<1 m2) and plot (2 × 6 m) scale. At field scale, soil loss samples were taken from 25 to 50 m intensively tilled runoff plots to assess SOC losses. At plot scale, selective erosion takes place as redistribution within the plot with crust formation. Thin sections demonstrate the horizontal structure of the particles on the surface covered by SOC and clay colloids. The rate of SOC enrichment is inversely proportional to the amount of soil loss. Enrichment is significant in the settled (coarse) part of soil loss, while – in contrast to the plot scale results – there is no SOC surplus in the suspended part. SOC components of high molecular weight seem to be increasingly vulnerable to erosion and they are overrepresented in soil loss. Because of their high stability carbon sequestration occurs in the buried horizons.