Fertigation refers to the application of nutrients to a crop through the system of irrigation.
The most common fertigation system is the application of water soluble fertilisers near the roots of plants through drip irrigation.
How does a venturi work?
Venturis work on a principle of differential pressure.
In short, water flows into the venturi at a higher pressure than that at which it exits. This pressure difference creates a vacuum at the suction port on the side of the device. This sucks air, ozone or liquid into the main water stream. So, the greater the difference in pressure, the greater the vacuum and, with that, the greater the efficiency of mixing.
If sized and installed correctly, a venturi can achieve a gas/water ratio of 1:1. (i.e. inject 1 litre of air/ozone into every litre of water that passes through it). For Liquid dosing this ratio is maximum 1:10 (i.e. inject a maximum of 1 litre of chemical into every 10 litres of water).
Venturis come in a number of different sizes. Size is determined not by the size of the pipeline into which it is installed, but rather by the pressure and flow rate of the water.
Which venturi do I need?
Wassertec are agents for Mazzei Injectors, which are made in the USA. Mazzei venturi injectors are engineered from highly chemically resistant Kynar (PVDF) and are available in sizes ranging from ½ inch to 12 inch pipe diameter. We keep stock of models in the ½ inch to 3 inch range. Other sizes are available on request.
Fertigation allows for a better distribution and uniform application of fertilisers as the fertilisers are dissolved in the irrigation water.
Every single plant in the field receives the amount of nutrients it requires accurately and uptake of nutrients is improved.
It saves time and labour as the fertilisers are not applied manually.
It allows for the adjustment of fertiliser requirements at each growth stage.
Since soluble fertilisers are applied in small quantities at the root zone, there is lower nutrient loss from the soil surface and there is no risk of nutrient leaching to the groundwater.
Crop yield is generally increased by 40% to 50% and the quality of produce is improved.
Disadvantages of fertigation
The design, installation and operation of a fertigation system may require the assistance of a professional
The cost of a fertigation system is high
Pressurised drip fertigation system using a water pump
The components of a pressurised drip irrigation system include:
– a plastic container (for field of 1 arpent, minimum capacity of 50 L) to dissolve fertilisers in water
– a Venturi pump (min. 25 mm [¾”] – max. 50 mm [1½”]) to inject the dissolved fertilisers into the irrigation system
– a water pump to operate the drip irrigation system
– a screen filter to remove impurities from the fertiliser solution to prevent clogging of the drip system
Information Source – Food and Agricultural Research and Extension Institute
Fertigation South Africa – Contact Us