Joint International Conference on Long-term Experiments ...

2. Sample preparation
Collected soil samples are handed and prepared as follows: samples were dried and
drilled. Before grinding, samples were cleaned from plant remains and other possible
dirt, and pass a 2 -mm screen. Finally, samples were stored in plastic boxes in dry place
until the examination according to Hungarian guideline (MSZ 20135:1999).
3. Procedure of biological and chemical soil analysis
A modified periodical incubation experiment is carried out in the laboratory to
determine the actual rate of N-mineralization (Stanford and Smith, 1972; Filep and
Tóthné, 1980; Filep and Ferencz, 1999). We improved conditions of this modified
incubation apparatus.
The enlarged amount of soil (without quartz sand) is supported in a leaching glass tube.
A thin glass wool pad is placed above and below the soil sample to avoid soil dispersion
when the leaching solution is poured into the tube. It is leached free of mineral N and
then incubated at optimum temperature (35°C) and moisture (WC=75%) for 16 weeks.
100 ml of 0.01 M CaCl2 solution is used for each N removing operation. So this way the
mineralized and easily soluble organic N of soil was removed periodically. Vacuum is
applied only to remove excess solution.
The leachates of incubation and the chemical extractions are analysed for mineralized N
(sum of nitrate and ammonium nitrogen) and organic N according to the method
described by Houba et al., (1986). The different N forms were analysed by autoanalyser
(SKALAR Segment Flow Analyser - CFA system).
The main advantage of this method that both the 0.01 M CaCl2 soluble inorganic Nform
and the UV digestable organic-N form of soil are determined simultaneously
(Nagy, 2004).
We used N-free nutrient solution containing 0.007 M CaSO4∗2H2O; 0.002 M MgSO4;
0.01 M Ca(H2PO4)2 and 0.015 M K2SO4 for use in replacing nutrients. The leaching
process is repeated after 2., 3., 5., 7., 9., 12., and 16 weeks.
The incubation can be terminated when cumulative N mineralization approaches a
plateau.
RESULTS AND DISCUSSIONS
The incubation was applied for chosen samples 1998 and 2001 as mentioned above. The
Nmin and Norg content of soil was measured along the incubation. The pH, the cumulated
values of Nmin and Norg and the results of chemical extraction are shown in Table 3.
1. Results of chemical examination
The pH of soil of experiment was strongly acid as earlier results (Kádár et al., 1999) and
the result of control showed.
Mostly the one sided N and NP, NK, NPK treatments had decreased the pH, due to
the acidic effect of applied fertilizers and their long term using. Note, that only the
liming treatments could hinder the further acidification and increased the pH.
The amount of 0.01 M CaCl2 soluble mineral N was between 2.55 and 9.63 mg/kg
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