The effect of energy plantations on the depth distribution of soil nitrate-ions

Tolner László 1 – Vágó Imre2 – Sipos Marianna2 –Tolner Imre3 – Füleky György1

1Department for Soil Science and Agricultural Chemistry, Szent István University, Gödöllő, Hungary

2Department for Agricultural Chemistry and Soil Science, Debrecen University, Debrecen, Hungary

3 Hungarian Institute of Agricultural Engineering, Gödöllő, Hungary

Due to leaching to the deeper soil layer nitrate ions may get out of the root zone of crop plants; so they can reach the ground water without any object as well. In this case the way the nitrate entered the upper soil layer – fertilizers, manure, communal or agricultural sewage or its sludge – is unimportant. The microbial degradation of the nitrogen containing material towards the deeper layers is even less possible.

The effect of different nitrogen fertilization dosages (0 – 360 kg ha-1) has been investigated on the maize production within the confines of a twenty-year long-term field experiment on a ferruginous soil at Gödöllő Szárítópuszta. Depending on the treatments, a significant amount of nitrate entered the deeper soil layers. After the termination of the long-term experiment the plant nutrition experiment has been turned into an environmental protection one. Since then the way, how the harmful effects of previous long-term fertilizer application can be dissolved, has been investigated. We set up an experiment with alfalfa as a plant with deep root system for four years. After this we planted acacia into the plots of the previous intensive fertilizer long-term experiment.

Before and ten years after the plantation we took soil samples every 20 cm till 3 meters depth. By the measurement of the soil samples taken before the acacia plantation it was stated, that in the plots treated with higher fertilizer dosages a significant nitrate accumulation can be observed below the 2 meters depth. This accumulation disappeared within the next ten years, while the total nitrate content of the soil profile did not change significantly. In this case nitrate accumulation has only been reported in the topsoil, due to the activity of the nitrogen binding bacteria in the nodules of the legume acacia. As a consequence of the long-term experiment the experimental area became rather heterogenic. This manifested in the different growth and development of plants grown on plots with different treatments. After 10 years the heterogeneity of the site showed a significant decrement, which resulted in homogenous plants. This change can be followed well by using remote sensing technologies as well.