Drip irrigation, as is well known, offers many advantages and among them also allows the use of the fertigation technique.

What is the fertirrigation?

Fertigation is the agricultural technique by which fertilising elements dissolved in the water are applied to the roots of the plants by means of the irrigation system.

In concrete terms, it is a technique that allows the drip irrigation system to be used also for fertilisation. However, it would be a mistake to consider this technique the simple combination of irrigation and fertilization phases using the same tool, on the contrary it is a method that allows to increase crop yields and obtaining a saving on fertilizer costs: in fact the use of fertilizers is carefully dosed and applied in a targeted way in order to avoid waste and side effects.

Pros and cons

This technique undoubtedly has its strengths, but it would also be appropriate to take into account the critical points, here a small summary of both:

Pros

– better fertilization efficiency;

– increase of production yields;

– saving on labour costs;

– localized fertilizer distribution and subsequent control/reduction of fertilizer purchase costs.

Cons to be considered

– requires additional costs for the installation of the mixing plants;

– requires more professionally trained personnel;

– in case of extremely rainy seasons, there is a risk of a fertilisation shortage.

Required tools

Fertigation uses the drip irrigation systems, but this does not mean that the same system without any modification can be converted for water and fertilizer supply.

There are some tools to use, the main ones are:

– water

– fertilizers

– solution dosing device

– filters

Water

Although it may seem a commonplace, water is a necessary tool because it is the vector with which the fertilizer is distributed to the crop. A constant control of water quality is crucial, on the importance of this aspect we have dedicated an ad hoc article on our blog that you can find here.

Fertilizers

Generally, in fertigation, the main types of fertilisers used are two:

– water soluble fertilizers

– acids

Water soluble fertilizers

There is a wide variety of water-soluble fertilizers on the market, when choosing them we recommend to pay attention to:

– title

– solubility and presence of insoluble residues

– forms of nitrogen

– chlorine and sodium content

– typology

Acids

Acids in irrigation are mainly used to correct the pH of the water.

The amount of acid used to neutralize the bicarbonates does not alter the salinity and therefore the EC of the water, making it possible to add part of the fertilizers through the acids.

The acids used in irrigation are nitric acid, the most widely used, sulphuric acid and phosphoric acid.

As dangerous substances, their sale and use is regulated by law (DL 52/1997).

Dosing devices

For the injection of fertilizer there are several solutions, the most used are:

– Venturi injector

– mechanical positive displacement pumps

– electric pumps

– computerized fertirrigators

Venturi injector

It is the simplest and most economical device to use, requiring neither electricity nor major maintenance work. The only weak point is accuracy: the dilution ratio is adjusted only by means of valves and flow meters installed on the suction pipe and main line.

Despite everything it is an excellent tool, according to some experts the most suitable for field crops.

Volumetric dosing mechanical pumps

A piston pump uses the pressure of the water pipeline to move a second piston with which the solution-stock is sucked. The pump can be mounted in-line or on a by-pass, does not require electricity and has good accuracy. With the use of graduated nuts, it is possible to vary the dosage, however this system can cause calcium losses.

Electric pumps

The electric pumps, as the name suggests, are powered by electricity, but they have many advantages, including: having large flow rates, being modular and not producing pressure drops.

They are mainly of two types: diaphragm and piston.

– Electric diaphragm pumps are generally cheaper but have a lower flow rate than their piston counterparts. They are also affected by back pressure, which is why compressed air is used.

– Electric piston pumps, on the other hand, are more robust and precise and are not affected by back pressure. Depending on the type of control, the dosage is controlled in a certain way: in positive displacement pumps, the dosage is controlled by a litre counter (mechanical or electronic), in proportional control pumps the dosage is a proportion between the difference of the set values and those detected by the in-line probes.

Computerized fertirrigators

They are systems capable of preparing different nutrient solutions, they are mainly used in greenhouse crops.

These systems use common Venturi injectors connected to electronic flow meters and precision solenoid valves.

To conclude, the fertigation is an excellent technique to optimize crop processes and, although in theory it is not complicated, it still requires knowledge of certain aspects for optimal implementation.