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Venturi injector. Photo: L. Schwankl Naturally occurring chemicals in groundwater that is used for irrigation can leave chemical precipitates in emitters, such as calcium carbonate (lime), iron and manganese compounds, and iron sulfide.
Pump, filters, and injection system for a small drip irrigation system. Photo: L. Schwankl Of the commonly occurring chemical precipitates, lime (calcium carbonate) and iron (and manganese) are the most common in microirrigation systems.
Venturi injection system using a small electric pump Photo: L. SchwanklFertilizers are commonly injected into the irrigation water of microirrigation systems, a process called fertigation. Injection of fertilizers, however, can cause clogging problems in the emitters.
Sulfuric acid injection system to mitigate calcium carbonate clogging problems. Photo: L. SchwanklPrecipitation of calcium carbonate (lime) is a common clogging problem in microirrigation systems. Water with a pH of 7.
Empty storage reservoir used to settle out precipitated iron from a high iron groundwater source. Photo: L. SchwanklEven at low concentrations, iron and manganese can clog microirrigation systems. Iron is a more common problem because it is more plentiful than manganese.
A flow meter installed at the head of a microirrigation system or small flow meters placed at the head of selected lateral lines can help you detect clogging. Saddle-mount propeller meter installed at the head of a drip system. Note the instantaneous (gpm) and totalizing (gal) registers. Photo: L.
The best policy is to not mix fertilizers. However, if mixing is necessary for microirrigation, follow the considerations below. These considerations are based on information contained in a UNOCAL compatibility chart.
Mixing a fertilizer that contains calcium with one that contains sulfate can cause calcium sulfate (gypsum) to precipitate. One example of this occurs when you mix calcium nitrate with potassium sulfate.
Microirrigation system that uses a tablet form of sodium hypochlorite as a biocide. Photo: L. SchwanklAdding acid (e.g., sulfuric acid, phosphoric acid, etc.
Fan-jet style microsprinkler. Photo: L SchwanklA perfect microirrigation system would have every emission device (drip emitter or microsprinkler) discharging at exactly the same rate. This never occurs in the real world so expect to see discharge variability between emission devices.
