| Fertigation, as the name implies, is the applying of | | | | damages to the irrigation system and plants and |
| fertilizers through irrigation water: Fertilization + | | | | obviously, the efficiency of fertilization is reduced. |
| Irrigation. This relatively new technique is being more | | | | Importance of fertilizers solubility in fertigation |
| and more commonly used in recent years, but the | | | | Not all fertilizers can be used in fertigation: only water |
| term "fertigation" is still not well recognized and many | | | | soluble fertilizers are appropriate, but bear in mind |
| have not heard it. | | | | that they differ in their solubility under the same |
| Fertigation has many advantages over other | | | | conditions. Moreover, the solubility of each fertilizer |
| fertilization methods, and when properly used, it | | | | may change under different pH and temperatures. |
| saves time and labor, fertilizers application is more | | | | Mixing different fertilizers in the same stock tank |
| accurate and uniform, and nutrient uptake by roots is | | | | may also affect their solubility. More importantly, |
| improved. | | | | some fertilizers cannot be mixed together because |
| Two methods of fertigation: quantitative and | | | | of interactions that result in insoluble salts which clog |
| proportional | | | | the irrigation system and reduce the efficiency of |
| When using fertigation, fertilizfers solutions are | | | | fertigation (see Solubility article). |
| prepared in advance in stock tanks and the solution is | | | | Irrigation system plugging hazard: causes and solutions |
| then injected into the irrigation water. The most | | | | Fertigation is commonly practiced using micro-irrigation |
| common fertigation methods to do so are the | | | | systems, which are highly susceptible to plugging. The |
| quantitative method and the proportional method. | | | | causes of plugging may be particles in the water, |
| The quantitative method is commonly used in soils. In | | | | precipitation of salts or bacteria and algae growth. |
| this fertigation method, the grower first decides how | | | | Particles of sand and suspended debris are usually |
| much fertilizer he needs to apply per area (e.g. kg/ha, | | | | too large to pass through emitters, while silt-sized |
| lbs/acre). This quantity of fertilizer is then delivered | | | | and clay-sized particles do not normally cause |
| through the irrigation system. | | | | emitters plugging. This kind of plugging hazard can be |
| The proportional method is mostly used in soil-less | | | | predicted by measuring turbidity and performing |
| media and sandy soils. In this method a defined | | | | laboratory filtration test. Plugging with sand particles |
| quantity of the stock solution is injected into each | | | | and debris can be prevented by adequate filtration. |
| unit of water flowing through the irrigation system | | | | In fertigation, the irrigation water contain a relatively |
| (e.g. l/m3, lbs/gal). | | | | high concentration of dissolved salts. If the pH of the |
| Some fertigation controllers allow the grower to | | | | irrigation water is above 7.0, or if one or more |
| directly determine the required injection rate, while | | | | minerals are in excess, precipitation and emitter |
| other controllers require the input of time and flow | | | | plugging is highly probable. Precipitates of Calcium and |
| parameters (irrigation flow rate, irrigation duration, | | | | iron minerals are the most common. Preventing |
| injector discharge, injection duration). | | | | plugging in this case is by keeping the pH of the |
| Irrigation system design for fertigation | | | | irrigation water below 7.0 (slightly acidic) and avoiding |
| Effective fertigation requires knowledge and proper | | | | excessive application of fertilizers, beyond the crop |
| management. In fertigation, fertilizing is an integral | | | | requirements. Flushing the irrigation system before or |
| part of the irrigation system and therefore, the | | | | after each irrigation cycle can also prevent salt |
| irrigation system has to be properly designed. Here | | | | accumulation. |
| are some examples to be taken into consideration | | | | High levels of iron and hydrogen sulfide promote |
| for a good design: | | | | growth of bacteria, which create slime. Algae can also |
| Irrigation flow rate should correlate to the injector | | | | create slime. Slime accumulates in different parts of |
| discharge. For example, if the irrigation flow rate is | | | | the irrigation system and may cause emitter plugging. |
| too high, it won't be possible to inject the full amount | | | | Reddish slime indicates presence of iron bacteria, |
| of the needed fertilizer. | | | | while yellowish to white slime suggests that sulfur |
| Installing one-way valves in appropriate places in the | | | | bacteria are active. Preventing plugging by slime can |
| system prevents back flow of fertilizers to the | | | | be achieved by chlorination. If the source water is |
| pumps or into drinking-water lines. | | | | not chlorinated, it is a good practice to inject chlorine |
| Water meters installation is highly important. | | | | upstream to the filtration system. |
| The whole system should be well calibrated, including | | | | Annual maintenance of the irrigation system is |
| injectors, water meters, EC and pH sensors. | | | | extremely important for keeping the system in good |
| Inaccurate readings may result in untoward results, | | | | condition. |