Rotation: ideally, five years should elapse between carrot crops to avoid disease
buildup, especially where disease/s have been significant.
GROWTH CONDITIONS
Day length: long-day.
Growth period: the first thinnings can be eaten in about 35 days. The crop can then
be thinned again, and continuously harvested when needed for a period of several
months.
Temperature: carrots are a cool season crop, although there are varieties available
which are suitable for growing in highland areas of the tropics and subtropics,
normally planted in the autumn and winter.
Rainfall: the plants should be kept moist but not wet. If irrigated, this should be
plentiful so that the water goes deep down, encouraging the roots also to go down
deep.
Pests: the commonest and worst is the Carrot Root Fly; its maggots are about 8mm
long and eat into the outside of the carrots, leaving ugly marks which may also later
develop into rot. Leaves of infested plants tend to turn red. The adult fly can smell
carrots from several kilometres away, especially when the plants are bruised, so both
thinning and weeding should ideally be done in the evening and on wet days,
preferably in a light rain, or after a thorough watering. Methods to reduce the fly
problem include placing a barrier of netting 60–80 cm high all around the carrot
plants, eliminating all nearby weeds of the Umbelliferae family as these are alternate
hosts, putting soot or wood ash on the soil around the plant stems, spraying a
mixture of 30 cc of paraffin in 4.5 litres of water onto plants, or mixing paraffin with
sand and applying it on the soil around plants. Probably the most satisfactory way of
dealing with this almost inevitable problem is to try to deter the flies with
interplanting sage, onions and other Allium plants so the flies cannot detect the
distinctive carrot smell.Best of all, try earthing up.
Plant breeders have had some success in breeding carrot fly resistant varieties,
based on the partially resistant variety “Sytan” crossed with the Libyan species
Daucus capillifolius. Other partially resistant varieties include “Fly Away”,
“Resistafly” and “Maestro”.
Diseases: the fungus called Carrot Disease causes brown spots to form on the roots,
then tiny red spores on the soil surface. Minimised by burning all infected roots, applying
a mixture of 2:1 sulphur:lime to infected soil and rotating five years between carrot
(orUmbelliferae/Apiaceae) crops.
- Storage Diseases—carrots should be stored dry, and so they should not be washed
before storage—all earth and plant tops should be removed, and the roots stored in a
cool, well ventilated place—2–5C is ideal.
YIELD
Yields of carrots are very variable, according to the variety, growth period and
conditions, soil, rainfall, etc. In poorer conditions 3 or 4 MT per hectare is common;
modern cultivation techniques can produce yields 10–12 times higher.