Carrot (Revised)

General Information and Agronomic Aspects

Introduction

Daucus carota, commonly known as the carrot belongs to the family Apiaceae and the genus Daucus. It is a biennial plant that is widely cultivated for its edible root, which is consumed as a vegetable worldwide. The genus Daucus comprises about 75 species, with Daucus carota being the most well-known and commercially important species. Daucus carota is cultivated in various regions of Africa, including North Africa, East Africa, and parts of West Africa. It is well-suited to different climates and can be grown in cool climates both in the tropical and temperate regions. The plant prefers well-drained soil and requires moderate water supply. 
Carrots are primarily utilized for culinary purposes, both raw and cooked. They are consumed in various forms, including salads, soups, stews, and as a standalone vegetable. They are valued for their crisp texture, sweet taste, and high nutritional content. Carrots are an excellent source of dietary fiber, antioxidants, vitamins, and minerals. They are particularly rich in beta-carotene, which is converted into vitamin A in the body. Vitamin A is essential for maintaining healthy vision, promoting proper immune function, and supporting overall growth and development. Vitamin A deficiency can lead to blindness and especially for children to a greater risk of dying from ailments such as measles, diarrhoea or malaria. Carrots also contain significant amounts of vitamin C, vitamin K, potassium, and other beneficial compounds that contribute to their health benefits. Young leaves are sometimes eaten raw or used as fodder.
The market for carrots is significant both globally and in Africa. Carrots are one of the most consumed and widely traded vegetables worldwide. They are readily available in supermarkets, grocery stores, and local markets in various forms. In Africa, the demand for carrots is driven by domestic consumption, with a growing interest in processed carrot products.
(Van der Vossen & Kahangi, 2004. Kew botanical gardens).

Species account

Carrot is slender, annual or biennial herbaceous plant that grows up to 1 to 3 feet (30 to 90 cm) tall. 
Foliage: Leaves: are pinnately divided and deeply dissected into narrow segments. Flowers: The stem is coarsely hairy and, during flowering time produces flat-topped clusters of small flowers called umbels, with a central dark purple flower surrounded by white ones. The flowers eventually turn into dry, brown fruits called schizocarps, which have spiny bristles. Carrots have a long, edible taproot with other small sider roots which allows it to efficiently access water and nutrients from the soil. The taproot vary in color from orange to purple, red, white, or yellow, depending on the cultivar.
Carrots are biennial, meaning they complete their life cycle over two years. In the first year, they develop a rosette of leaves and store energy in their taproot. In the second year, they send up a flower stalk and produce seeds (Tran G., 2016).

Carrot varieties
Carrots exhibit significant variation in color, size, shape, flavor, and texture. They come in shades of orange, red, purple, yellow, and white, with sizes ranging from slender to stout. Flavors can vary from sweet to earthy, and textures can be tender or crisp. This diversity allows for versatile culinary applications and customization.

Table 1: Examples of carrot varieties and their qualities

Ecological conditions 

Carrots can grow under a range of climatic conditions, but they perform best under moderate temperatures. They are mostly cultivated as a cool season crop. Seed germination occurs between 7degC and 30degC. Optimum air temperatures are 16-24degC. Soil temperatures above 25degC may reduce root quality, including root color. High temperatures can cause burning of young seedlings. For economic yields, carrots should be grown in tropical regions at altitudes above 700 m. Early-maturing carrot cultivars may grow in the lowlands, but yields will be low and roots will have a poor color. 
Carrots grow best in a well-drained friable loam free of stones and hard soil clods. It is a short season crop of 2-3 months with the potential of high yields for family food security and fresh market sales. It does well in the cooler areas of Kenya under both rainfed and irrigated conditions. 

Agronomic aspects

Carrots are propagated by seeds. Seeds are sown, often mixed with sand, 1/2 - 1 cm deep in drills 10-15 cm apart in finely prepared soils previously cultivated to a depth of at least 30 cm. Lightly aerate the soil by shallow digging before sowing carrots or sow them in ridge culture (small dams of 10 to 20 cm height) to facilitate mechanical weeding, thinning, and to limit soil borne diseases. In addition, this will allow easier penetration by the carrot root and will also improve water holding capacity. 
Seedlings are thinned to 5-8 cm in the rows. Seed requirements (200 plants/m2 and 70% germination) for the dominant half-long carrot cultivars used in Asia, are 4-5 kg/ha. For bigger carrots, the density may be reduced to about 100 plants/m2. Carrots that bolt (produce seed) in between normal carrots should be pulled out and fed to livestock. Seed produced this way will not produce good quality carrots. Seed production under tropical highland (above 1200 m) conditions is possible by selecting and harvesting the best quality mature carrot roots and replanting them separately in a corner of the field. Bolting and seed setting soon follows. 

Husbandry
Crop rotation is essential to reduce soil-borne diseases and pests. Mulching (rice straw or dried grass) after sowing is recommended to encourage germination. Seedlings may be earthed-up when roots start swelling to keep them cool and prevent green tops. Temperature of 15 to 20degC is optimal for seed development. In hot weather, light overhead shade is beneficial. Under such conditions carrots grow well under the canopy of fruit trees. Irrigation during dry spells is necessary to prevent irregular root development. Nutrient requirements of carrots are particularly high for potassium (200-300 kg/ha) and low to medium for nitrogen (0-90 kg/ha). Carrots are sensitive to high Chlorine concentrations and more susceptible to diseases at very high soil ph. Liming is recommended when pH is below 5.5. Well-decomposed organic manures are beneficial when applied moderately (10-20 t/ha). Fresh organic matter such as farmyard manure or manure from a leguminous crop can induce forked roots, which are difficult to clean and to market.
Young carrot seedlings are weak and grow slowly. Therefore, it is essential to keep weeds under control for the first few weeks after germination. Cultivate shallowly with a hoe.
Deep cultivation may injure the roots. Weeding and thinning of young plants can be very labor intensive, for which reason most families grow fairly small beds at any one time. 

Intercropping 
Because of their limited space requirements and early growing habits, carrots are ideal for intercropping between other crops such as tomatoes, lettuce or capsicums and because of their fragrant leaves can help keep pest levels low. Other crops good for intercropping with carrots include garlic, dwarf bean, onion, parsnip, leek, small peas, pea mange-tout (snow peas), and radish. The most profitable example of an association is that of carrots and leeks. Carrots have very deep roots that extract nutrients deep in the soil, whereas leeks have extremely superficial roots, which help the crop to extract nutrients near the soil surface. Moreover, carrots can drive away worms from leeks, while leeks can drive away flies from the carrots (TOF No. 8, page 8).

Harvest, post-harvest practices and markets

Harvesting
Carrots are mostly harvested manually by pulling up the roots at the leaves as long as the soil is moist and soft. If the soil has dried, it will be necessary to use either a spade or similar tool to loosen the soil and harvest the roots. Carrots are usually ready for harvesting 60-85 days after sowing. Mature roots should be orange-coloured internally down to the blunt tip. 

A good market price can be fetched from young carrots with a fresh top, but leaving the top on dries out the root quickly and reduces the marketing period of the crop. An alternative is to trim the top back to about 2 cm and package attractively. 

For mature carrots the tops are trimmed down completely to avoid storage rots before marketing. Carrots can remain in good condition for 100-150 days when the foliage is removed and they are stored at 1-4° C with 95-100% relative humidity. Carrots should be stored separately from other vegetables to prevent a bitter flavour induced by ethylene (a colourless gas with a sweet odour that is produced by many fruits and vegetables that accelerates the ripening process). Generally carrots store better when they are mature and harvested under moist conditions, and undamaged and free of diseases and pests.

Post-harvest practices.

Carrots bundled with leaves can be stored for up to three weeks in a cool place. However, for longer storage (100-150 days), it is recommended to remove the foliage, store the carrots at 1-4°C with 95-100% humidity, and keep them separate from other vegetables to prevent a bitter taste caused by ethylene exposure. High dry matter content, low organic matter soil, mature harvesting under moist conditions, and undamaged, disease-free carrots contribute to better storage. Carrots can be graded by weight (A: <50g, B: 50-200g, C: 200-400g, D: >400g). Exported carrots are washed, graded, and packaged in perforated polythene bags. However, small-scale farmers in Africa may experience post-harvest losses by transporting topped carrot roots in sacks to local markets (Van der Vossen, & Kahangi, 2004).

Value addition and markets 
Carrots enjoy widespread consumption and have diverse markets globally. Key consumers for carrots include households, restaurants, food processing companies, and the fresh produce industry. Carrots are widely used in various culinary applications, including salads, soups, stews, side dishes, and as ingredients in processed foods like juices, purees, and baby food. The value addition of carrots involves processing them into various products such as carrot juice, puree, frozen carrot cubes, and dehydrated carrot flakes. These processed forms have an extended shelf life and can be used in the food industry as ingredients or additives in a wide range of products. 
Carrots hold significant market value globally and are widely produced and exported. According to NAB 2022 report, global carrot production has witnessed a growth trajectory, rising from 40,265,109 tonnes in 2015 to 44,762,859 tonnes in 2019. Furthermore, predictions indicate a continued upward trend in the coming years. Leading countries in global carrot production and export include China, the United States, Russia, Ukraine, and Poland. Europe is reported to be the fastest growing market for carrots, whilst North America namely Canada and the United States of America hold the largest carrot markets.
In Africa, several countries are prominent in carrot production and export. Based on estimates from FAOSTAT 2021, the top six leading carrot producers in Africa from 2016 to 2020 include: Algeria, Morocco, Egypt, Kenya, Nigeria and South Africa. (beef2live.com, NAB, 2022, FAOSTAT, 2021).

Nutritional value and recipes

Carrots are a nutritious vegetable that offer a wide range of health benefits. They are rich in vitamins, minerals, and antioxidants, while being low in fat and proteins. Carrots have a low glycemic index, which is especially beneficial for diabetic patients. The water content of carrots varies from 86% to 95%, and the edible portion contains about 10% carbs, mainly in the form of sugars like sucrose and glucose.
The fiber present in carrots aids digestion and promotes weight loss. Vitamin A, crucial for vision, development, and immune function, is found in higher amounts in orange carrots. Cooking carrots and consuming them with fat enhances the absorption of vitamin A compared to eating them raw. Biotin (vitamin H) supports fat and protein metabolism, while B6 is involved in converting food into energy. Vitamin K1 and calcium are important for blood coagulation and bone health, and potassium helps control blood pressure.
Carrots are packed with carotenoids, powerful antioxidants that can reduce the risk of heart disease, degenerative diseases, and certain types of cancers. Lutein, found in carrots, plays a role in preventing age-related macular degeneration. Additionally, red and purple carrots contain lycopene, which may lower the risk of cancer and heart disease. (Bjarnadotti, 2015, da Silva Dias, 2014, Varshney & Mishra, 2022). 

Table 2: Proximate nutritional composition of 100 g of Carrot. 

Source (Nutrient data): FAO/Government of Kenya. 2018. Kenya Food Composition Tables. Nairobi, 254 pp. http://www.fao.org/3/I9120EN/i9120en.pdf

^$ Draining the water several times leaches away water soluble nutrients significantly.

^a Lewis, J. 2019. Codex nutrient reference values. Rome. FAO and WHO

^b NHS (refers to saturated fat)

^c https://www.hsph.harvard.edu/nutritionsource/water/

^d British Heart Foundation

^e FDA

^f NIH

^g Mayo Clinic

^hWest African food composition table, https://www.fao.org/3/ca7779b/CA7779B.PDF

Complimentary recipes