What is Fertigation ?

By Lize Reinecke, Amy Grundling & Adelene van Zyl 

Fertigation is the process of nutrient application through irrigation where nutrients are introduced to the watering system used for irrigation. Fertigation can be applied either through a drip or a spray irrigation technique. It is used to regulate the amount and duration of fertilizer application, the dilution of the fertilizer in the water as well as the start and ending times of the fertigation process.

In the nursery industry fertigation has become increasingly popular due to the high efficiency rate. Most growers use injectors to mix concentrated fertilizer solution into the irrigation system. A large variety of injector are available to meet the different needs of any size nursery. Well-designed systems can be monitored at different stages in the process to ensure that the injectors work efficiently and that the plant receive the correct amount of nutrients.

​The nutrient solutions are prepared in stock tanks from where it is injected into the irrigation water tanks. For fertilizer to mix with irrigation water, the fertilizer must be at a higher pressure than the irrigation water, that is why it is referred to the fertilizer being injected into the irrigation water.

Types of Fertigation
There are four categories into which fertigation can be placed: Continuous, Three Stage, Proportional and Quantitative Application. The choice will depend on crop response and the risk of excessive nutrient runoff.

1. Continuous Fertigation Application refers to a continuous flow of fertilizer along with irrigation water.
2. Three Stage Application fertilizer is only injected into irrigation after the crop have been irrigated and the soil is wet and after the fertilizer has been applied, it is flushed from the soil.
3. Proportional Fertigation Application refers to the direct proportion between the amount of fertilizer in the water and the amount of water used for irrigation.
4. Quantitative Fertigation Application refers to the specific amount of nutrient application to each different block.

​Advantages and Disadvantages
The advantages of fertigation include the precise control of both the concentration and balance of nutrients, an equal distribution of fertilizer, increased penetration of fertilizer in soil, decrease in nitrogen loss and nutrient solutions can easily be customised for any plant growth stage or species. Disadvantages of fertigation include high levels of toxicity in the irrigation system which can damage nursery crops and the environment,  frequent mixing and applying of liquid fertilizers increase labour cost, clogging of irrigation pipes and exposure to high levels of fertilizer may result into health problems.
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Fertigation can be applied from a small nursery to large commercial farming. This method enables farmers to lower their input cost through precision farming and maximise their production. However, it is important that fertigation systems to be monitored and managed frequently to prevent any damage.