Matching nitrogen demand of plants and N release of organic fertilizers with respect to amount and timing is one key for successful cultivation of organic ornamentals. Thereby for plants with a low to moderate N demand growers can add the fertilizer as complete preplant application (CPA). For plants with a high N demand splitting fertilization in a reduced preplant application combined with an additional fertigation (RPA+F) is preferable. Aim of the current research was the investigation of N release of organic fertilizers in incubation experiments. Results of the incubation experiment were linked to a pot trial with pelargonium. Incubation experiments reveal that most
fertilizers release about 40 to 50 % of total N and most nitrogen is released within the first 21 days. Only for sheep wool a delay of N release up to ten days was found. CPA using sheep wool and RPA+F (irrespective of fertilizer) give the best results. The delayed release pattern of sheep wool seems to match best N demand of plants
