*5.4.3 Fertilizer application*

According to Alhaji Adamu Shekari while describing the importance of of applying fertilizer to ginger stated that "the profit of ginger farming is determined by fertilizer" [89]. The general view from farmers indicated that fertilizers are applied three times during the growing period of ginger. The first is during field preparation which is mainly organic manure. Respondents gave reasons for this practice that inorganic fertilizers may cause the young ginger plants to wilt or die because it may be too hot for them when applied. This agrees with the findings of [90] that organic manure like ash has high pH of about 10.2 that neutralizes soil acidity. The next fertilizer applications involved majorly inorganic fertilizers like NPK or Urea which are applied after second and third weeding.

### *5.4.4 Harvesting*

Maturity of ginger is usually reached when leaves of ginger plant begin to turn yellowish brown in color indicating readiness for harvest. Harvesting is done by digging out the tuber majorly by male workers while female workers or children collect the tuber into containers.

#### **5.5 Garlic** *(Allium sativum***)**

India produces average yield of about 5.23 t/ha making it one of the world's largest garlic producers [91]. Spain, Egypt, Korean Republic, Argentina, Italy, China, and the United States are other growing countries. According to [92], garlic production is about 10 million tonnes per annum which represents only ca. 10% of bulb onions production. Garlic has been cultivated for decades in the northern states of Nigeria like Kano, Sokoto, Borno, Bauchi, Jigawa, Katsina, and Zamfara [93]; and garlic production figures in Nigeria are shown in **Figure 5**. Its wide distribution is denoted by its common "native" names in different societies. It is called "Tafarnuwa" in Hausa and "Ayu" in Yoruba [94].

#### **Figure 5.** *Production/yield quantities of garlic in Nigeria.*

*Nigeria Root Vegetables: Production, Utilization, Breeding, Biotechnology and Constraints DOI: http://dx.doi.org/10.5772/intechopen.106861*

#### *5.5.1 Climatic and soil requirements*

Garlic can grow well in both tropical and sub-tropical environment [95] but it is a cold weather perennial crop that has a high requirement for nutrients and water [96]. It grows well in region with 600–1200 mm annual precipitation and temperatures ranging between 5–25°C and 25–40°C [97]. Fertile loamy soils free from stone and gravels and that is well-drained is suitable for garlic production. Heavy soils are unsuitable for growing garlic because the bulbs produced under such condition will be deformed and difficult to harvest [97].

#### *5.5.2 Seed preparation and treatment*

Garlic cloves that are about 8–12 g in size which are detached from the bulbs and soaked in clean water for about 6 h before planting and removal of the outer skin from the bulblets and dried are used as planting materials. These cloves are mixed with fungicide and insecticide to control fungicides and seed attacking insects before planting [97].

#### *5.5.3 Planting*

Garlic has fibrous root and the bulbs comprise small bulbils referred to as cloves, which are the vegetative planting materials for the crop [98]. Garlic can be planted either by dibbling, drilling or broadcasting [97]. Dibbling method is commonly practiced, it involves putting one clove in a hole 7 × 15 cm at a depth of 3–6 cm, placing the growing point upwards and covering lightly with soil. About 350–600 kg cloves are needed to plant one hectare corresponding to 400,000– 500,000 plants/ha [97]. Garlic produces well when cultivated on fertile welldrained sandy or silt-loam soils with good moisture retention capacity [99]. Ahmed et al. [100] recommended large clove size and irrigation at 3-day interval for good performance under semi-arid conditions like Sokoto in Nigeria.

### *5.5.4 Fertilizer and its application*

Nitrogen is a major nutrient required for growing garlic. Bulb growth was significantly affected by applied nitrogen [101]. Longer leaves and higher number of leaves were recorded when nitrogen rate was increased to 100 kgN/ha [102]. In another experiment [96], increasing rates of nitrogen application to 150 kgN/ ha increased growth and yield components of garlic but higher rates of nitrogen above 150 kg significantly reduced growth and yield. Farooqui et al. [103] reported that 200 kgN/ha significantly increased yield parameters such as neck thickness, bulb diameter, number of cloves/bulb and fresh weight of 20 cloves. However, at Samaru, Nigeria [104] growth and yield of garlic was significantly increased with application of nitrogen with 15 t/ha recorded as maximum yield when 90 kgN/ ha was applied. Meanwhile, [105] reported significant increase in bulb yield with application of 75 kgN/ha but clove weight increased only at 150 kgN/ha after which a significant decrease was observed. Magaji et al. [99] recommended application of 50 kgN/ha for improved plant height (cm), number of leaves/plant, leaf area, number of bulbs, and the total yield of the garlic.

#### *5.5.5 Harvesting*

At 18 weeks after planting when leaves of garlic are partially dry and bend to the ground, it is assumed that garlic has reached optimum maturity period and the bulbs are harvested [97].
