USE OF THE NMIN-METHOD FOR OPTIMIZATION OF VEGETABLE NITROGEN NUTRITION
The maximum yield of marketable leeks and cabbages was obtained at a total nitrogen supply of 220 and 320 kg N per ha respectively. The root zone taken into consideration was 50 and 100 cm respectively. However, in carrots no yield response to increasing nitrogen supply was found and the optimum nitrogen supply was set to 60 kg N per ha. Since the amount of soil mineral nitrogen in the root zone can be balanced following different previous crops in each year by adjusting fertilizer N applications, the Nmin-method was found to be a valuable aid in specifying the application of nitrogen fertilizer. Compared to barley, the nitrogen effect of cabbage as a previous crop corresponded to 50 and 90 kg N per ha in leeks and cabbages respectively.