Dehydrogenase activity of some Hungarian soils as related to their water and aeration status.

Four horizons (till the depth of 130 cm) of six typical Hungarian soil profiles (Fluvic Gleysol, Vertic Gleysol and Orthic Solonetz) were investigated in order to determine relation between dehydrogenase activity, oxygen diffusion rate (ODR), redox potential (Eh) as well as Fc +2 content and the soil water status, and to relate them to the soil utilisation and cultivation type. The experiments were performed with the use of undisturbed soil samples preincubated on the water tension plates at 0, 63, 159 and 500 hPa at room temperaturc. All the investigated parameters varied widely in the tested soils. Dehydrogenase activity and reduced iron content decreased but ODR and Eh values increased with increasing soil water tension. A close relationship between oxygenation indicators (ODR, Eh and Fc +2 ) and dehydrogenase activity was found. The most sensitive oxygenation parameter for describing the relationship between enzyme activity and soil aeration status appeared to be ODR. The studied soils showed a significant decrease of Eh as well as tendency to diminish their ODR, dehydrogenase activity and reduced iron content due to deep-loosening cultivation.