YIELD AND NITRATE CONTENT OF CARROTS (DAUCUS CAROTA L.) AS AFFECTED BY NITROGEN SUPPLY

In order to derive recommendations for the nitrogen (N) fertilization of carrots with high yield and low nitrate content, the effect of different levels of nitrogen fertilization was tested for the cultivars Ingot (medium early harvest, fresh market) and Karotan (late harvest, processing). Data was taken from field experiments carried out in 1992 and 1993 on a sandy soil where 0, 50, 100 and 150 kg N ha^-1 had been applied. In both cultivars, all fertilizer treatments led to nitrate contents of carrot roots lower than the German nitrate threshold value for baby food (250 mg NO₃ kg^-1 on a fresh weight basis). Treatments had no significant effect on either yield or nitrate content.

From the experimental data and from results found in the literature, it was concluded that no nitrogen fertilizer should be applied for medium early carrot cultivars (total yield approximately 80 t ha^-1) in sandy soils with average nitrogen mineralization rates and that for late cultivars with higher yield (approximately 110 t ha^-1) a soil mineral N target value of 75 kg N ha^-1 is appropriate.