Timing Nitrogen Applications for Quality Tops and Healthy Root Production in Carrot

Abstract

When carrots (Daucus carota L.) are mechanically harvested, sufficient nitrogen (N) must be balanced between the roots and carrot tops; weak tops reduce yield. A 2-year study was conducted in Montcalm County, Michigan, where four replications of four N treatments (45, 90, 135, and 180 kg ha⁻¹), were arranged in a randomized complete block design. Results showed the importance of determining pre-existing N sources, in as much as the deep taproot of carrot accessed unmeasured N in the subsoil and nitrate concentrations in irrigation water added N. The greatest yield occurred at 153–189 kg ha⁻¹ available N while tops continued to take up N through 200–232 kg ha⁻¹. When the last N application was made less than 35 days before harvest, the rate of N uptake exceeded dry-matter accumulation rate.

Keywords:

• Daucus carota L.
• petiole sap nitrate
• residual nitrogen
• timely applications