| Abstract: | Nitrogen uptake of kohlrabi, estimated by growth stages and an empirical growth model Some fertilizer recommendation systems for field vegetables are based on estimated nitrogen uptake curves. The estimation of nitrogen uptake should be as accurate as possible. Therefore 3 estimation methods and their accuracy (standard error of difference between measured and estimated values, sd) are compared. Comparisons were carried out with measured nitrogen uptake curves of kohlrabi (Brassica oleracea var. gongylodes L.) from 16 field experiments. The use of observed growth stages resulted in the smallest estimation error (sd = 14 kg N · ha?1). This method is recommendable because it is accurate and easy to use. Estimations by applying an empirical nitrogen uptake model (sd = 16 kg N · ha?1) are more complicated. The estimation based on time after planting is easy to use but showed the largest estimation error (sd = 28 kg N · ha?1). |
