ESTIMATION OF NITROGEN UPTAKE OF FIELD VEGETABLES
For kohlrabi, the use of observed growth stages resulted in a small estimation error (sd=14kg N ha-1). This method is recommended since it is accurate and easy to use. The estimation that depended on time-after-planting, showed a larger estimation error (sd=28kg N ha-1). For white cabbage, both methods tested were not suitable because estimation errors were too high (63 and 51kg N ha-1, respectively).