Agriculture uses the majority of the potable water available on the planet, with irrigation accounting for 70% of global water withdrawals. The irrigation equipment used has an important role in water use and irrigation efficiency. For an irrigation system to be considered efficient, water distribution needs to be uniform within the line (≈10%), and pressure variation across the secondary line should be lower than 20% (Burt et al., 1997). After installing the irrigation system, growers must ensure it matches the project design in the field. Pressure, water flow and distribution, and efficiency coefficients are necessary to evaluate system performance (Silva and Silva, 2005).
Drip irrigation has become one of the most common systems used for agriculture due to the potential for high irrigation efficiency (>90%) and the application of low water volumes (1–150 L·h−1), resulting in water savings when compared to sprinkler irrigation (Testezlaf, 2011). Drip irrigation applies water directly to the root zone, thereby increasing water and nutrient use efficiency, increasing yield and crop quality, and maximizing profitability (Borssoi et al., 2012). However, the initial deployment cost is usually higher than that of overhead/sprinkler systems. Drip irrigation demands constant maintenance and requires efficient filtration due to the possibility of emitter clogging (Testezlaf, 2011).
The Agricultural Experiment Station of the University of the Virgin Islands initiated an irrigation research project in the early 1980s with the objective of increasing vegetable production while conserving water resources (Palada et al., 1995). Since then, farmers shifted from sprinkler to drip irrigation (also known as microirrigation). However, most of the U.S. Virgin Islands local farmers use drip tapes with noncompensating emitters. The water output of nonpressure-compensating emitters varies as the line pressure changes, which may result in inefficient water application (<70%) (Dogan and Kirnak, 2010). Pressure-compensating emitters apply the same amount of water at each emitter over a range of different line pressures (i.e., 70–350 kPa). These emitters can be used in long lines, irregular or mountainous areas, and where precise watering is desired (Dogan and Kirnak, 2010). When water resources become limited, especially during years affected by severe drought, as occurred in 2015 in the U.S. Virgin Islands and California, it is necessary to improve irrigation management and equipment efficiency to save water and pumping energy.
The performance evaluation of drip irrigation systems is simple, and instructions and results are widely available in the literature (Pereira et al., 2012). However, few farmers run performance tests regularly. This is mainly due to the lack of knowledge about the importance of managing irrigation systems properly. Consequences include reduced crop yields and wasted water resources. To improve irrigation performance, it is necessary to promote the use of irrigation scheduling methods, improve system design and equipment performance, and enhance farmers’ skills to manage irrigation systems efficiently (Pereira et al., 2002).
Okra (Abelmoschus esculentus) is one of the most important and widely grown crops found throughout the tropical and subtropical regions (Eshiet and Brisibe, 2015). It is an annual, erect-growing, high-yielding crop with numerous cultivars varying in plant height, degree of branching, pigmentation of the various parts, period of maturity, and pod shape and size. Okra is mainly grown for its tender green pods, which are cooked and commonly consumed as boiled vegetables. Despite its enormous economic benefits, okra rarely reaches its maximum yield potential due to several constraints (Eshiet and Brisibe, 2015). Some of the major factors limiting okra production include the use of locally unimproved varieties, high incidence of pests and diseases, a narrow genetic base of existing varieties, and lack of proper irrigation to control plant growth.
Driven by the desire to indicate the best irrigation equipment for local growers to save water and select more adapted genotypes in okra, the objective of the current study was to determine the performance of four pressure-compensating and noncompensating emitters and the effects of these irrigation equipment types on the yield of three okra varieties cultivated in the U.S. Virgin Islands.
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