We examined the changes in the CO2 emission of the soil in the Westsik’s crop rotation long-term experiment. The experiment located on the fields of DE AKIT Research Institute in Nyíregyháza. The main aim of this experiment is to maintain or increase the fertility of the sandy soil. The following fertilizer methods are applied: farmyard, straw and green manures, and combinations of these manuring methods with NPK fertilizer. The soil of this experiment is slightly humous, acidic, loose sandy soil.

The straw manure and the farmyard manure treatments resulted in higher soil CO2 gas emission, than the green manure application. Even so, we consider the straw and farmyard manure application to be not harmful because these manures increase the crop and resulte in higher soil humus content as the green manure application.

Keywords: CO2 emission, organic amendment, long-term experiment