Ultimate Carrot Cultivation Guide

Carrots provide both backyard and commercial farmers with a relatively easy crop. Carrots are a good option to farm as they can be produced on small tracts of land and are not very heat sensitive. There are four (4) types of cultivars of carrots, which can be farmed in Zimbabwe. The classifications are based on root shape and storage capability.

Cultivars

1.   Chantey: This type has very strong foliage and its roots are broad in the shoulder, relatively short and blunt-tipped. They have a strong pale-coloured core and store well. The main use is for processing.

2.   Nantes: Nantes types have sparse foliage that is weakly attached to the crown. The root is moderately long with a uniform diameter along the length and a rounded tip when mature. The surface is thinner and easier to scar. The highly pigmented core is poorly developed making roots brittle and it matures easily. Nantes is less suitable for long-term storage.

3.   Danvers: The Danvers type has strong foliage with roots that are moderately wide in the shoulder, pointed and longer than Chantey types. Core development is strong with medium pigment. This type stores well and is used in processing and fresh market.

4.   Imperators: Have strong foliage and roots that are narrower in the shoulder than Danvers type. The roots are long and slender, tapering to a pointed tip. Core development is moderate and medium pigmented. It has good storage quality and is used for the fresh market.

Climatic Requirements

The carrot is a cool weather crop but also does well in warm climates. The optimum temperature for growth is between 15 to 20°C. Temperatures below 10°C cause longer, more slender and paler roots.

Rainfall

Carrots require a steady supply of moisture and it must be maintained above 50% of available moisture throughout growth. Generally, carrots require approximately 25mm of water per week but under warm dry conditions, 50mm will be required.

Soil Requirements

Requires deep loose, well-drained sandy to loam soils, that are not subject to capping, and optimum pH of 6.0 to 6.5 are ideal for carrot production. The crop produced in humus-rich soils tends to increase in foliage excessively and forms forked and hairy carrots. The roots also tend to be rougher and coarse on the outside. Black soils should also be avoided, as carrots are very sensitive to saline soils.

Propagation

Carrots are only propagated by means of seeds.

Soil Preparation

The soil should be well tilled and as level as possible in order to obtain a good stand. It must have a good crumbly structure and kept moist enough to allow seed germination. Therefore, the soil must be deep ploughed to loosen the soil to a depth of at least 30cm. The soil should be fumigated for nematodes.

Planting

Carrots can be grown all year round with irrigation. The best time, however, is between February to September.

The rows are generally spaced from 200 to 400mm apart. In double or triple rows, the width between sets of rows range from 400 to 600mm. Row spacing in baby carrots production maybe 100mm. A planting density of 150 to 160/m² give good results in double rows whereas density of 100/m² is deal for single rows.

The seeds are directly sown in the fields on ridges or raised beds. Row planting is preferred to broadcast sowing. The seeding depth should be 10 to 25mm or 40mm in loose, light sands. Planting depth should be shallow on heavier soils and colder months. Slightly deeper planting is recommended in summer when the soils dry out quickly. The chance of a successful establishment of the crop will be increased if the seed is sown in moist soil and only if the soil is kept moist.

Thinning

Thinning is usually necessary in carrot production and should be carried out when the ground is moist, preferably in the late afternoon.

Fertilisation

Fertiliser recommendations should be based on soil analysis. For basal fertilisers, it is generally recommended that one uses 600kg/ha of compound J (14:6:20 4S 0.0.4B) which is incorporated in the soil before planting. Top-dressing on the other hand requires about 100kg/ha Potassium Nitrate (13:0:46) along the rows at 3 weeks after emergence.

Carrots have low nitrogen requirements and good yields can be obtained with 80kg/ha of nitrogen applications. Nitrogen can be applied at planting and the remainder at 4 to 8 weeks after emergence. Forty kilograms of phosphorous per hectare are sufficient to produce a good crop. The crop has a high potassium requirement and half is applied as side dressing at 4 to 8 weeks after emergence.

Irrigation

The soil should never be allowed to dry out. Too much moisture causes short carrots with light colour and a larger diameter. The field should be irrigated lightly immediately after sowing. Irrigation water should be applied once or twice a day using a solid set sprinkler system. Watering should gradually be reduced to prevent longitudinal splitting of the roots when the crop approaches maturity. Water stress during root development also causes cracking of the roots, which also become hard.

Pest Control

1. Aphids

They suck sap from the plants resulting in retarded growth, yellowing and restricted seed production.

Control: Control can be achieved by spraying with a registered pesticide. Malathion 25 WP and Dimethoate 40 EC are very suitable.

2. Red Spider Mite (Tetranychus Cinnabarinus)

Red spider mite is generally not a serious pest in carrots but the numbers can increase rapidly as it gets warm.

Control: Control can be achieved by using Windmill’s registered pesticides, Malathion 25 WP and Dimethoate 40 EC.

Disease Control

1. Alternaria blight (Alternaria dauci)

Symptoms are dark brown to black spots, some with yellow edge, appearing on the leaves. The oldest leaves are more susceptible than younger ones. The petioles and roots can also be affected. It can be transmitted with the seed and cause damping-off of the seedlings and usually occur during wet weather.

The disease can be controlled by disinfecting seed with a seed dressing containing Thiram or Captab or sowing certified seed. Mancozeb/Dithane can also be used. Crop rotation is recommended.

2. Bacterial blight (Xanthomonas carotene)

This disease is characterised by brown spots developing on the leaves and brown stripes and on the petioles. In seed crops, the flower stems and inflorescence can be affected, whereas in carrots, brown horizontal lesions appear on the leaves.