SOIL AND PLANT-TISSUE TESTING FOR NITROGEN MANAGEMENT IN CARROTS

Carrots (Daucus carota L.) were grown in mineral soils with one of sev eral nitrogen (N) programs during two years. Nitrogen management based on the available soil N content (nitrate plus ammonium) in the top 30 cm was compared with increasing amounts of N applied in multiple appl ications. Available soil N was monitored throughout the growing season . Nitrate-N concentration in the petiole sap and in the root tissue wa s measured while the roots were sizing. In both years, total and marke table carrot yields were maximized with the N program which accounted for available soil N in the top 30 cm in mid-June. Applying more N inc reased top biomass and nitrate-N concentration in the carrot root whic h resulted in higher residual soil nitrate-N after harvest in 1993. In sufficient N resulted in a greater incidence of foliar disease in the late fall. The nitrate-N content of the expressed petiole sap related directly to the amount of N applied. An accounting of N inputs and pla nt accumulation indicates that carrots are very effective in utilizing indigenous and applied N.