On the responses of carrots (Daucus carota L.) to nitrogen supply

Conflicting reports of the responsiveness of carrots (Daucus carota L.) to nitrogen (N) fertiliser have been rationalised on the basis of the climatic zones in which the experiments were conducted. We tested this explanation with two experiments under temperate conditions, where yield increases were predicted to be unlikely, yet growers frequently apply N fertiliser. Our results show that in temperate regions carrot yields may indeed respond to N fertiliser when the yield potentials are c. 140 t ha(-1) of fresh roots, if soil mineral N to 0.6 m depth and readily mineralisable N add to less than c. 190 kg N ha(-1). With normal experimental precision, such responses may be undetected unless soil water deficit is kept small and variations in plant population are accounted for. Carrots have strong potential for luxury uptake of N. This has implications for marketing and the possible use of carrots as catch crops.