Joint International Conference on Long-term Experiments ...

enign materials in agriculture. Numerous researchers studied products from mining
and industry for increasing the organic and inorganic colloid content of sandy soils and
for improving their water and nutrient management (Blaskó, 2005). Zeolites (Kazó,
1981; Köhler, 2000), ground rhyolite tuff, ground basaltic tuff, and bentonite (Köhler,
2000; Lazányi, 2003) have already been examined.
Carbon is an essential element of life, a composer of live and dead organic matter,
the carbon cycle is a basic process of the biogeochemical cycle (Jolánkai et al., 2005).
Microorganisms play an extremely important role in transforming organic matter into
inorganic matter and in the cycles of the different elements including carbon. For
describing the transforming processes, intensity of cellulose-decomposition (Kádár et
al., 2005), carbon-dioxide production of soils (Zsuposné Oláh, 2005; Varga et al. 2005),
and the amount of carbon in the microbial biomass are used (Szili-Kovács et al., 2005;
Szili-Kovács 2006; Lukácsné Veres et al., 2006).
With special regards to the requirements of sustainability, we joined an experiment
of sand melioration, in which we studied the effect of bentonite, a natural, clay-like
stone rich in colloids, and bentonite composted with manure on the moisture content,
pH, nutrient management and microbial activity of soil, which is demonstrated via
specific elements of the carbon cycle.
MATERIAL AND METHODS
The small-plot experiment was set up at the experimental farm of the Nyíregyháza
Research Centre of UD CAS in October 2002. Samples were collected from the top 2-
20cm layer of soil. The in vitro experiments were carried out at the soil microbial
laboratory of the Department of Soil Sciences, UD CAS FA between 2003 and 2005.
The soil type was brown forest soil with alternating layers of clay (”kovárvány”), with
sandy texture and acidic pH (pH(H2O) 5.28; pH(KCl) 4.33 ). The soil was deficient in
nitrogen, the level of phosphorus and potassium supply was medium and satisfactory,
respectively. Treatments were performed with increasing dosages of bentonite and
bentonite composted with manure (Table 1).
From the physical parameters, moisture content was determined after drying to
constant mass at 105 0 C (Klimes-Szmik, 1962). From chemical soil parameters, pH was
measured in suspensions with distilled water and KCl (Filep, 1995). The nitrate-N
content of soil was determined with the Na-salicylate method (Felföldy, 1987), while
the easily soluble phosphorus and potassium content of soil was measured with 0.1m
ammonium-lactate (AL) extractor (Gerei, 1970).
The amount of microbes in the soil was determined by the plate dilution method
from soil-water suspension as the total number of bacteria (on Bouillon agar) and the
number of microscopic fungi (on peptone glucose agar) (Szegi, 1979). The number of
cellulose-decomposing bacteria was determined by the method of the most probable
number of bacteria according to Pochon et al. (1962). Regarding soil microbial activity,
the carbon-dioxide production of soil was measured according to the method of
Witkamp (1966. cit. Szegi, 1979), while the soil biomass-C production and saccharase
enzyme activity were determined by the fumigation-incubation method (Jenkinson et
al.,1976) and the method of Frankenberger et al., respectively. The statistical analysis
was performed using the SPSS 9.0 program
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