In this paper we show the effect of different organic fertilisers on the EDTA-soluble zinc content of soil. Data were collected from the Westsik’s long-term crop rotation experiment, established in 1929. The experiment presents different fertilisation methods: main-, and second crop green manure, straw-, and farmyard manure. Treatments were done with or without NPK fertilisation. No zinc fertilisation was performed in the experiment. The soil of the experiment is acidic and loose sandy soil with low humus content. Data from the year 2011 were used for the analysis.

The applied NPK fertilisation had no effect on the zinc content of soil. The soluble zinc content of soil was similar in treatments with the same organic fertilisers irrespectively of artificial fertilisation. The methods of organic fertilisation resulted in difference in the zinc content of soil. The soluble zinc content of soil in the fermented straw manure treatment was higher by 0.4 mg kg-1 than in the green manure treatment of lupine, the main crop. This difference is considerable in the case of loose sandy soil. The zinc content of the soil can be further increased with straw manure than green manure.

The difference was not significant between the green manure treatments of the main crop and the green manure treatments of the second crop. Comparing the organic fertilisation methods, the highest zinc content of soil was reached by farmyard manure. Even in the soils with low zinc content, the suitable zinc supply can be reached by regular application of 26.1 t ha-1 farmyard manure.

There was moderate positive, significant correlation between the zinc and humus content, zinc and AL-soluble P2O5 content as well as zinc and pHKCl. The increasing humus content, AL-soluble P2O5 content and soil pH could result in increased zinc content.

Keywords: zinc, organic amendment, Westsik’s long-term experiment