Influence of lime and farm yard manure

2.4. Generality on Carrots

2.4.1. Botanical description

The carrot belongs to the botanical family of Apiacea. The scientific name is Docus carrota .It is an annual or biennial erect herb up to 50 cm tall at the mature vegetative stage and up to 150 cm tall when flowering .It has taproot fleshy ,straight ,conical to cylindrical,5-50 cm long and 2-5cm in diameter at top, orange (most common), reddish violet, yellow or white.

Leaves in a rosette at base of plant ,but alternating on flowering stems,2-3 pinnates ; stipules absent ,petiole long, sheathed at base, petiole and rachis pilose, segments divided into oblong to lanceolate or linear unequal rays ,strongly contacted in fruit, involucral bracts, pinnatipartite or pinnatisect, with linear lobes. Flowers mainly bisexual, but male flowers present in addition to bisexual flowers, often few dark purple sterile flowers present in the centre of umbel, 2mm in diameter,5-merous;pedicel 0.5-1-5 cm long; calyx with small teeth or absent ;petals fee, white or pinkish ,often enlarged in exterior flowers of umbel, stamens free, Ovary inferior, bristly ,2-celled,styles 2 (Grubben, et al 2004).

2.4.2. Ecology

According to Grubben, et al. (23004), supposedly wild (or neutralized), Daucus carrota plants occur in Eritrea and Ethiopia at 1800-2100 m altitude.

In their adaptation to the northern latitudes of Europe, carrots became biennial. Long days during the vegetative phase before vernalization do not cause bolting. They require vernalization at low temperature to reduce flowering .Carrots adapted to tropical and sub tropical latitudes respond to long days by bolting even before the roots have properly thickened .Carrots are mostly cultivated as cool season crop. High soil temperature, in excess of 25 ⁰C, induces slow growth rates, fibrous roots and low carotene content. For economic yields, carrots should be grown in tropical regions at altitudes above 1200m or during the cool winter months in sub tropics. Early-maturing carrot cultivars may grow in the lowlands but yields will be low and roots will have a poor colour. Optimum air temperature is 16-24^OC.Soil should be well drained, fertile and of sandy texture. Heavy clay soils may induce malformed and twisted roots and harvesting will be difficult. Optimum pH is 6.0-6.5 (Grubben, et al 2004).

2.4.3. Fertilization.

For the yield of 20 tones of tap roots, the exportation is 85 kg of N, 20 kg of P, 60 kg of Ca and 15 kg of Mg. The optimum dose of fertilizers to be used depends on the reserve of soil nutrients in the soil and the required yield.

The carrots require the fertilizer that has high K content. The dose of N-150 kg /ha, P-100kg /ha and K-200 kg/ha is appropriate. The carrot is sensitive to high concentration of Cl, and is also sensitive to low pH (Grubben et al, 2004).

According to Grubben and Denton (2004), the liming or the use of fertilizers containing Ca, is recommended when the pH is below 5.5, the organic matter well decomposed is profitable at a moderate dose (10-20tone).

The soil concentration in Mg must be moderate. The deficiency in Mg causes the leaves chlorosis, especially on old leaves, which can dry. The high concentration of Mg is harmful (Evers, 1998).According to Villeneuve and Leteinturier (1992), the Sodium improves the quality of tap root, increases the resistance to low temperature and increases the yield. The carrot is sensitive to Zinc and Bore deficiency.