While the high initial investment associated with drip irrigation may appear prohibitive for pineapple culture, in areas where water is limited or expensive and the need for irrigation may extend for many months, the investment will pay good dividends. Drip irrigation allows precise placement of water in the root zone in volumes that match the crop's consumptive demand. Drip irrigation is especially effective during the first few months after planting, when a consistent but low-volume supply of water is needed for the developing root system.
Drip-irrigation systems involve the following major components: a water source, a filtration system if particulate matter that can clog emitters is present, chlorination to prevent microbial growth in the drip tubes, a system of in-field distribution pipes, which bring water at the correct volumes and pressures to various parts of the fields, and the emitter tubes, which are usually buried just below the soil surface between two lines of plants.
The emitter tubes are usually custom-made for pineapple to allow for a slow release of relatively low volumes of water. If the soil has good hydraulic conductivity, the slow release results in wider spreading of the water in the root zone. Flow rates will depend on orifice spacing, orifice diameter and line pressure, and these variables will depend on the soil type and cost and avail ability of water. The length of run for emitter tubes will depend on the slope of the terrain, but should be limited to lengths that will result in output variations along the tubes of no more than 10%. As with overhead irrigation, scheduling includes a consideration of rainfall, with the younger plants taking precedence over the more established ones.
Drip irrigation may be used to safely deliver water-soluble fertilizers, nematocides and fungicides to the root zone. However, drip irrigation does not guarantee the desired effects from these materials, as their dispersal and reaction in the soil are largely uncontrolled and may not be as well understood when compared with the standard methods of application. For example nitrogen is easily leached with excess irrigation and, like other nutrients, is recovered by the crop according to the distribution and vigour of the roots.
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