Test PB Collection: FTE

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.

The irrigation water used in a microirrigation system should be carefully evaluated to assess any potential clogging problems. Analyzing Irrigation Water Irrigation water should be analyzed for the following. electrical conductivity (EC), which is a measure of the total dissolved salts (TDS).

Table 1 provides criteria for assessing the potential of an irrigation water to cause clogging. Other quality considerations include the following. Bicarbonate concentrations exceeding about 2 meq/l or 120 mg/l and pH exceeding about 7.5 can cause calcium carbonate precipitation.

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.

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.

Microsprinkler Photo: L. Schwankl The treatment to solve a clogging issue in drip systems generally depends on the cause of the clogging. Particulate clogging problems result when there are particles (sand, silt or clay mineral material or other contaminants) suspended in the water.

Microirrigation on young almonds Photo: L.