The Effect of Irrigation Frequency and Amount on the Growth and Yield of Kale (Brassica Oleracea var. Acephala)

Kale is botanically known as Brassica oleracea var. Acephala, belonging to the family Cruciferae / Brassicaceae. It is regarded as a winter vegetable, easy to grow, and the leaves can be continuously harvested throughout its life cycle. It grows well in moist but well-draining soils. Kale tolerates slightly acidic soils with a pH range between 5.5 – 6.5 that has plenty of organic matter such as compost (Hodges, 1991). Cultivars of this vegetable differ primarily in plant size, leaf colour and texture. Some varieties that are sold as "flowering kale" are used as ornamental plants or for decoration. Eswatini import approximately 37,300 metric tonnes of fruits and vegetable with a value of US$11,000,000 from South Africa (NAMBOARD, 2018). This is because the annual rainfall distribution in the country is skewed, with the most rainfall 1,500 mm received in the Highveld region and the least 450 mm in the Lowveld region (Dlamini and Khumalo, 2019). The Lowveld is the ideal place for vegetable production, but due to lack of water, rural communities struggle to make ends meet. Vegetable production can only be a success if grown under irrigated conditions. However, the energy requirement associated with irrigation makes its adoption difficult.

Vegetables are a necessity in rural communities as they provide the people with most of the required nutrients. Kale though a highly nutritious vegetable is hardly grown due to lack of water and the technical know-how on its agronomic requirements. The adoption of low energy agricultural technologies like drip in the country is very slow, as the Eswatini government tends to promote conventional methods of water resource development as opposed to micro irrigation which is ideally suited to smallholder farmers (Manyatsi and Magongo, 2008). Drip irrigation can be more efficient than sprinkler and furrow irrigation (Hunsaker et. al., 2019; Bajracharya and Sharma, 2005) since only the root zone of the cropped area is irrigated (Dukes et. al., 2006 and Hartz, 1999). It places water and nutrients were they are needed most with minimal energy requirements.

A majority of the soils where vegetables are grown are sandy with very low water holding capacities. These require frequent irrigation and fertigation to minimize crop stress and to attain maximum production. The main drawback with drip systems is the frequent emitter blockages (Zhou et. al., 2019). Vegetables are easier to grow and many like kale are considered as food components that significantly influence human health and well-being (Dunja et al., 2018). Dunja et al. (2018) also noted that other authors have also recognized that the vegetable kale, among cabbages, was the best source of vitamins (A, B1, B2, B6, C and E), folic acid and niacin, fatty acids, and essentials minerals (especially K, Ca, Mg, Fe and Cu) (Ayaz et al. 2006; Jahangir et al. 2009; Eryilmaz Acikgoz and Deveci 2011; Thavarajah et al. 2016) but their level may depend on the environmental and growing factors (Fadigas et al. 2010; Bjorkman et al. 2011; Westwood et al. 2014). Since the capital cost of drip irrigation is beyond the reach of many rural farmers (von Westarp et. al., 2004; Sandhu et al., 2019; Holmer and Schnitzler, 1997) including Eswatini, the bottle drip system (Dlamini and Khumalo, 2019; Darouich et al., 2014) offers a feasible option for economic production in areas of low rainfall or during periods of water scarcity. A bottle drip system is an easy way of watering plants (Darouich et al., 2014), no costs is involved in purchasing the bottles as old material is useful, no power or piping required to supply the water and it’svery easy to make (Isaac, et al., 2013). The purpose of this study was to evaluate the effectiveness of using spent two (2 L) litre plastic bottles as a medium of irrigation on the growth and yield of kale (Brassica Oleracea var. Acephala) grown at Luyengo, Eswatini.