An on-farm field trial was set up in an organic greenhouse in order to balance the N-uptake by a sweet pepper crop and the mineralization of the organic fertilizers was applied. The effects of six fertilizer treatments were compared regarding yield, nutrient availability and mineral balance. Application of high levels of compost turned out to be favourable in order to reduce surplusses of available-N on the short term. On the long term, such high levels of compost are unfavourable as a high pool of mineralizable-N in the soil organic matter restricts the possiblities for precise fertilization adapted to plant uptake. Application of lower levels of farm yard manure in combination with additional fertilization with feathermeal turned out to be a good fertilization strategy both on the short and the long term unless there is a need for minimizing salt levels in the applied fertilizers
