Carrots

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Daucus carota

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General Information

Carrots (Daucus carota L. ssp. sativus) are cool-season biennials that are grown for the thickened root it produces in its first growing season. Although carrots can endure summer heat in many areas, they grow best when planted in the cool season. Carrots are rich in carotene (the source of vitamin A) and high in fibre and sugar content.

Suitable varieties for organic production

It is important that season specific varieties for summer or winter are used.

Planting

Carrots are sown directly on the field. To achieve a high percentage of germinating seeds, the soil structure should be well prepared (no excessive tillage). Seeds need to be planted near to the surface and be covered lightly with 0.3-0.6cm of soil. Germination is slow and irregular.

Design of the rotation

Carrots may be rotated with alfalfa or other leguminous cover crops; such as small grains, onions and spinach. To reduce soil borne diseases, rotation with celery, parsley, beets and sesbania has to be avoided.

Harvest and post-harvest handling

Handling

Carrots harvested and handled in hot weather are more likely to decay, and care should be exercised in handling to prevent wilting. Mature carrots are well adapted for storage and are stored in large quantities during the fall and winter for both the fresh market and processing. Careful handling during and post-harvest helps to ensure safe storage by avoiding bruising, cutting and breakage.

Storage

Mature topped carrots can be stored up to 9 months between 0° and 1°C with very high relative humidity: from 98% to 100%. However, even under these optimum conditions, 10% to 20% of the carrots may show some decay after 7 months. Under commonly found commercial conditions (0° to 4°C) with 95% relative humidity, 5 to 6 months storage is a more realistic expectation. Prompt cooling to 4°C or below after harvest is essential for extended storage. Poorly pre-cooled roots decay more rapidly. Carrots lose moisture easily, resulting in wilting.

Humidity should be kept high. Carrots stored at 98% to 100% relative humidity develop less decay, lose less moisture, and remain crisper than those stored at 95% relative humidity. A temperature of –1°C to 1°C is essential if decay and sprouting are to be minimized. With storage at 4 to 10°C, considerable decay and sprouting may develop within 1 to 3 months. Many potential decay causing organisms are removed by washing. Also, clean, washed carrots allow better air circulation. Air circulation between crates of pallet boxes in which carrots are stored is desirable to remove respiratory heat, maintain uniform temperatures, and help prevent condensation.

Bitterness in carrots, which may develop in storage, is due to abnormal metabolism caused by ethylene. This gas is given off by apples, pears, and certain other fruits and vegetables and from decaying tissues. Bitterness can be prevented by storing carrots away from such products. Development of bitterness can be avoided by low-temperature storage, as it minimizes ethylene production. Some surface browning or oxidative discoloration often develops in stored carrots.

Sources and References

Bibliography

FiBL, Research Institute of Organic Agriculture, Switzerland (2011). African Organic Agriculture Training Manual. Soil Fertility Management. [Accessed 19 March 2012]

FiBL, Research Institute of Organic Agriculture, Switzerland (2011). African Organic Agriculture Training Manual. Conversion to Organic Farming. [Accessed 19 March 2012]

FiBL, Research Institute of Organic Agriculture, Switzerland (2011). African Organic Agriculture Training Manual. Crop Management. [Accessed 21 March 2012]


FiBL (2011): African Organic Agriculture Training Manual. Version 1.0 June 2011. Edited by Gilles Weidmann and Lukas Kilcher. Research Institute of Organic Agriculture FiBL, Frick. [Accessed 12 July 2012]

FiBL, Research Institute of Organic Agriculture, Switzerland (2011). African Organic Agriculture Training Manual. Soil Fertility Management. [Accessed 19 March 2012]

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