Tóth, T., L. Kuti, I. Forizs and S. Kabos. 2001. Temporal changes in the factors of soil salinization at the
study site "Nyírolapos" of Hortobágy. (Hung.) Agrokémia és Talajtan. 50:409-426.

We examined the temporal changes of the salt accumulation and salt concentration in a 800x300 m study 
site of Hortobágy, Eastern Hungary using 420 aboveground EC measuring points, 7 groundwater wells 
and 3 soil profiles through repeated observations.
We showed that we can forecast the groundwater level with acceptable accuracy based on the sum of the 
precipitation. As the consequence of periodically appearing waterlogging, the direction of groundwater 
flow can change, and flow from the lower areas towards the higher ones.
In the groundwater wells the EC was closely correlated to the sum of the monthly precipitation and the 
EC value of the previous month.
Despite the short distances between the observation wells, there were differences between the 
composition and temporal variability of the oxygen, hydrogen and stable isotopes in the groundwater. The 
deep upwelling Pleistocene water, the evaporation from the groundwater and the precipitation are in 
equilibrium in the lowest lying salt-affected soils covered by meadow vegetation. We observed the 
strongest upwelling of the deep waters in the area of the most salt-affected soils.
We proved the free mixing of the groundwater and precipitation, based on the ratio Br-/Cl- ions in the 
"Salt affected meadow" profile. In the saturation extract of the "Artemisia grassland" and the "Achillea 
grassland" profiles the Cl- concentration was larger than in the groundwater, which suggests large 
evaporation.
As a consequence of the above observations, we found large soil salt concentration values only in the 
flow zone of the very saline groundwater in the "Salt affected meadow" profile. The salt accumulation 
levels of the very saline "Artemisia grassland" soil showed large salt concentration during the observation 
period. In the profile of "Artemisia grassland", which is placed at the highest elevation, we showed large 
salt accumulation during one month at the bottom of the B horizon, while in the A horizon we found 
strongly fluctuating, but small salt concentration. 
The conceptual model that was set up, separately describes the salt accumulation for dry warm and wet 
periods. The most important factors in the model are the elevation, the surface plant cover, temperature, 
water regime of the soils and the periodically appearing waterlogging, therefore the direction of the 
groundwater flow changes from time to time.