Micro-Irrigation for Greenhouse Crops
Maintenance of Micro-Irrigation Systems
The major cause of failure in micro-irrigation systems is emitter plugging. Emitter plugging can severely degrade irrigation system performance and application uniformity. Because the emitters are small and can easily plug, it is important to understand the maintenance requirements of these systems and be proactive to prevent plugging.
Filter Maintenance
Filters are the first line of protection for your micro-irrigation system, and they need regular maintenance to operate at a high level. A pressure drop across the filter is an indication of debris, so it must be monitored to maintain full flow. Pressure drops can be detected by installing gauges before and after the filter or a differential pressure gauge that compares the two sides. Monitor the filter pressure differential frequently, especially as water conditions change through the season.
Flushing the Main Lines, Submains, andLaterals
The main lines, submains, and particularly the lateral lines should be flushed periodically to ensure sediments are cleared from the system, which can cause a potential hazard by clogging emitters. Flushing the main, submain, and laterals will considerably reduce the accumulation of organic and mineral materials in the system. This will prevent those materials from reaching the drippers and eventually clogging them, thus minimizing the quantity of chemical products required to maintain the system. Regular flushing of the main, submains, and laterals will result in a significant saving of labor time and chemicals. The main, submains, and laterals in the system should be flushed in sequence. Flush valves should be installed at the end of the mains, submains, and laterals (if present). Main lines and submains are flushed by opening the flush valve(s) built into the system for that purpose.
Emitter Inspection
Systematic checking is required to spot malfunctioning emitters or to use accurate flow and pressure measurements and analyze their rates of change over time. Slow clogging causing partial blockage results from sediments, precipitates, organic deposits, or mixtures of these. Physical deterioration of parts is a concern with pressure-compensating emitters. The flow passage may slowly close as the compensating part wears out. Mechanical malfunction can also be a problem in flushing emitters.
Acidification to Remove Mineral Deposits
Mineral precipitates can form deposits (scale) that clog emitters. The most common deposits are calcium or magnesium carbonates and iron oxides. Since precipitation occurs more readily in water with a high pH (above 7.0), precipitation of these compounds can be prevented by continuous injection (whenever the system is operating) of a small amount of acid to maintain water pH just below 7.0. A more popular control method is to remove deposits as they are formed by periodic injection of acid. Enough acid should be injected continuously for 45 to 60 minutes to reduce the water pH to 4.0 or 5.0. Phosphoric acid (which also supplies phosphate to the root zone), sulfuric acid, or hydrochloric (muriatic) acids are commonly used.
Chlorination to Control Algae and Bacteria
Chlorine injection will prevent clogging of lines and emitters by algae and bacterial slime. Continuous injection of small amounts of chlorine maintains low concentrations of chlorine in the system and prevents their growth. However, periodic injection of larger amounts of chlorine is the preferred treatment for controlling algae and bacteria in drip systems.
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