In the years 2009 -2010 experiments on the influence of irrigation and mulching on yield of celeriac were carried out on certified organic field of the Re-search Institute of Vegetable Crops, Skierniewice. In the experiments three objects of irrigation: drip, mini-sprinkler and without irrigation and tree objects of mulching: mulching with textile biodegradable fleece, red clover mulching and without mulching were compared. In 2010 additionally textile biodegradable fleece enriched in dry red clover was used. Irrigation was applied on the base of soil moisture measurements by irrometers and it was started when water potential reached -20 kPa. Irrigation had a significant effect on the yield of celeriac. In the first year of experiment yield of irrigated celeriac was about 45% higher that non irrigated one. However no differences were found between two different systems of irrigation. In the second year drip irrigation increased yield of celeriac by 16,1% and mini-sprinkler irrigation by 12,1% in comparison to non irrigated object. Similar yield of celeriac was obtained in treatments with textile biodegradable fleece mulching and control without mulching in the first year of experiment. However red clover mulching increased yield of celeriac by 29% as compared to both fleece mulching and control ...