Szili-Kovács, T., T. Tóth, M. Halassy and K. Török. 2000. Restoration of sandy 
grasslands through the immobilization of soil nitrogen. 1. Laboratory incubation 
experiments. (Hung.) Agrokémia és Talajtan. 49:479-490.

The study aimed to select the appropriate type and dosage of carbon sources for 
the restoration of endemic sandy grassland (Festucetum vaginatae danubiale) in 
the Kiskunsag National Park by means of soil nitrogen immobilization. A 
laboratory incubation experiment was set up using soil samples collected from a 
field abandoned several years ago. The samples were taken from the 0-20 cm soil 
layer of the calcareous, sandy soil with low humus content in the Fülöpszállás 
region of the Kiskunság National Park. Various carbon sources (sucrose, starch, 
celluslose beads and sawdust), with varying decomposing rates were used 
separately and in combination to investigate the effect of carbon amendment on 
soil N availability. The regression parameters of a four-factorial quadratic 
model were evaluated at each sampling. The determaination coefficients of th e 
model were higher than 0.8 in all cases. All carbon sources added to the soil 
decreased the available nitrogen in the soil, but the extent and the dynamics of 
changes depended on the type of C source. A rapid decrease in available N was 
found in the first eight days of incubation, which was followed by a sow 
increase due to the remineralization of the immobilized nitrogen. Maximal net
nitrogen immobilization was observed after the 3rd day of incubation in the
presence of easily decomposable C sources. Nitrogen immobilization appeared
later and to a lower extent in the case of other C sources. The combined
application of carbon sources proved to be the most effective in maintaining
available N at a low level. Soil available N could be kept at a minimum level
for at least 78 days when applying 2 g/kg each of sucrose and sawdust together.