Tomato is a popular and versatile food crop grown and consumed all over the world and is the second most important commercial vegetable crop to potato (Solanum tuberosum) (Naika et al., 2005). It is one of the most widely cultivated vegetable crops in Africa, including Kenya. It is grown for home consumption in almost every homestead across the nation serving as an important source of vitamins and a cash crop for both small- and medium-scale commercial farmers. Apart from vitamins, tomato is also rich in lycopene, an antioxidant, which purportedly fights free radicals that interferes with normal cell growth and activity and thus reducing cancer, heart diseases, and premature aging (Nkondjock et al., 2005). The fruit also contain significant amounts of minerals and fiber. In Kenya, tomatoes always are in high demand both for fresh consumption and processing (Mungai et al., 2000).
Tomato are established by direct seeding or from transplants (Long and Cantliffe, 1975). However, reports have indicated that use of transplants is preferred because of higher plant survival, faster establishment, improved plant uniformity, earlier maturity, and reduced cost of production than direct-seeded plants (Leskovar and Cantliffe, 1994). Whether started directly or by transplants, optimum growth and quality of tomato is dependent on the environment. As a result, researchers have modified the environment to favor the growth of the plant (Caliman et al., 2010; Weerakkody, 1998). Tomato seeds are expensive and farmers in developing countries cannot afford poor germination as a result of unfavorable growing conditions [Horticultural Crop Development Authority (HCDA), 2006]. In addition, tomato seedling production in many parts of sub-Saharan Africa is faced with major challenges like unfavorable weather marked by limited or unreliable rainfall, high or low temperatures depending on the season, as well as severe pest infestation. These challenges are exacerbated by the fact that most tomato growing is by small-scale, resource-poor farmers who cannot afford expensive protected greenhouse crop production technologies. They must therefore produce their seedlings and crop in open fields subject to unfavorable growing conditions. The result of this scenario has been an increased cost of seed per unit area due to poor germination and pest damage. Insect pests like silverleaf whitefly (Bemisia tabaci), potato aphid (Macrosiphum euphorbiae), and western flower thrips (Frankliniella occidentalis) that transmit viral diseases are also experienced under such conditions. In a study conducted in Israel, Berlinger et al. (2002) reported effective management of tomato yellow leaf curl virus through physical exclusion of silverleaf whiteflies using the nets. On the other hand, the use of protected seedling culture has been shown to improve crop yields. In tomato, higher yields may be achieved with protected than nonprotected seedlings (El-Aidy and Sidaros, 1996).
In an effort to enhance emergence and growth of seedlings, growers normally use mulching as a cultural practice to raise seedlings and a microclimate modification strategy. However, some mulch material, especially organic mulch which is commonly used by small-scale resource-poor farmers in sub-Saharan Africa, harbors various seedling pests and diseases, resulting in additional pesticide and fungicide costs. Many concerns have been raised on the safety of these chemicals to humans and to the environment, and on their cost (HCDA, 2006; Martin et al., 2006; Ministry of Agriculture and Rural Development, 2003). Excessive use of these chemicals also results in the development of resistance in plant pests and diseases. Thus, the need to look into effective and safer eco-friendly methods of control is increasing.
Protected culture is predominantly used in temperate regions where seasonal agro-climatic changes restrict year-round cultivation of crops under open-field conditions. Due to this advantage, Iqbal (1987) recommended its applicability in tropical environments especially for cultivating high value crops such as tomato during the rainy season. One possibility of protected culture could be the use of EFNs. Nets have been used to protect crops from excessive solar radiation or other environmental hazards in developed countries (Majumdar, 2010). Use of EFN in protected cultivation has been tested and proven to be effective against certain pests of cabbage [Brassica oleracea var. capitata (Licciardi et al., 2007; Martin et al., 2006)], on alternaria blight (Alternaria brassicae), and on black rot (Xanthomonas campestris pv. campestris) of cauliflower (B. oleracea var. botrytis) seedlings (Kashyap and Dhiman, 2010). Also noted was reduction in pesticide use as a result of covering the crop with nets. In line with these observations, the current study aimed at investigating the effects of EFN on germination and performance of tomato seedlings in open fields.
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