Fertigation, delivering fertiliser through the irrigation system, is one of the most efficient ways to feed a crop. Done well, it puts nutrient exactly where and when plants need it, cuts waste and labour, and keeps growth even across a block. Done poorly, it blocks emitters, wastes expensive fertiliser and leaves patchy results. The difference almost always comes down to the injector at the heart of the system. This guide covers how water-driven fertigation works, how to choose the right injector for your operation, and how to set it up for consistent, reliable dosing. For the full range of injectors and fertigation equipment, see our agriculture and irrigation page.
Why water-driven fertigation suits Australian farms
Water-driven injectors are powered by the flow and pressure of the irrigation water itself. They need no electricity, no dosing controller and no external power at the point of injection. That matters on Australian properties, where the pump shed, the paddock and the block are often nowhere near mains power. Just as important, a water-driven injector meters concentrate in direct proportion to flow, so the dose stays constant whether the system is running one valve or ten. MixRite, Dosmatic and Chemilizer injectors all work on this principle, which is why they suit everything from a single greenhouse to a broadacre irrigation mainline.
How a fertigation injector works
As water flows through the injector, an internal piston or motor driven by that flow draws a fixed proportion of stock solution from the drum and blends it into the line. Because injection is tied to flow rather than time or pressure, the concentration downstream stays the same at high and low flow. Set a MixRite to 1%, and every 100 litres passing through the unit carries one litre of stock, whether that 100 litres goes through in a minute or an hour. This proportional behaviour is what makes water-driven fertigation so repeatable compared with manual batch mixing.
Inline or by-pass: two ways to plumb the injector
- Inline: the full irrigation flow passes through the injector. It is simple and accurate, and ideal for small to medium systems that sit within the unit’s working flow range.
- By-pass: only a portion of the flow is diverted through the injector, which doses that slipstream before it rejoins the main line. This suits higher-volume systems that exceed a single injector’s flow range, letting a Dosmatic or MixRite handle a large mainline without oversizing the unit.
Both by-pass and mobile fertigation setups are shown on our agriculture landing page, alongside the injectors that drive them.
Matching the injector to your operation
Three things decide the right unit: your flow range, your injection ratio, and the chemicals you are dosing.
- Flow: choose a unit whose working range covers your lowest and highest flow, not just the average.
- Ratio: MixRite and Dosmatic offer both fixed and adjustable ratio models, so you can lock in a set dose or dial it in to a target concentration.
- Chemical compatibility: match the injector’s seal materials to the fertiliser or acid you are running, especially for low-pH or aggressive nutrient mixes.
As a starting point: MixRite is a robust, proportional workhorse used across agriculture, livestock and sanitation; Dosmatic offers versatile fertiliser injection across a wide range of ratios; and Chemilizer uses proven diaphragm technology for accurate chemical dosing off the existing water supply. Our team can size and match any of these to your system. For a side-by-side comparison of flow, pressure and dose ranges, see our guide to choosing a water-driven dosing pump.
Mobile fertigation for nurseries and multi-block sites
Not every operation wants a fixed injector. Where you move between benches, blocks or greenhouses, a mobile setup travels with you. The MixRite Cart mounts an injector on a trolley for portable injection and dilution, and the Mobile Fertigator puts a Dosmatic SuperDos on wheels, both without electricity. For growers covering ground across a property, mobile fertigation removes the need to plumb an injector into every zone.
Getting the dose right
The injection ratio sets the proportion of concentrate drawn into the water, but the real goal is a target nutrient concentration at the emitter, usually measured in parts per million (ppm) of nitrogen. In short, your stock solution needs to be as many times stronger than the target as the ratio dilutes it: at 1:100, a 200 ppm target needs a 20,000 ppm stock. Whatever you calculate, verify it on commissioning with a simple volume or EC check rather than trusting the dial, and keep a calibration log. Our team can work through the numbers with you.
Protect your water supply
The moment you inject fertiliser or chemical into a water line, you create a path for that solution to travel back toward the supply if pressure drops. In Australia this is generally treated as a high-hazard cross connection that requires appropriate backflow prevention. Specify it at the design stage, not after the injector is plumbed in. Our Twist II Clean filter protects the injector and irrigation lines from grit. Have your plumber or a licensed installer confirm the backflow prevention your site requires.
Frequently asked questions
Do fertigation injectors need electricity?
No. Water-driven injectors such as MixRite, Dosmatic and Chemilizer run entirely on the flow and pressure of the irrigation water, so no mains power or controller is needed at the injection point. This makes them ideal for paddocks, orchards and remote blocks.
Which injector is best for fertigation, MixRite or Dosmatic?
Both are excellent water-driven fertiliser injectors. MixRite is a robust proportional workhorse used across agriculture and livestock, while Dosmatic offers a wide range of adjustable ratios. The best choice depends on your flow, target dose and chemical, which our team can match for you.
Can one injector dose a large irrigation system?
Yes, by plumbing it in a by-pass configuration. Only a portion of the total flow passes through the injector, which doses that slipstream before it rejoins the mainline, so a single unit can serve a much larger system without being oversized.
Can I move a fertigation injector between blocks?
Yes. The MixRite Cart and the Mobile Fertigator mount an injector on a trolley for portable, electricity-free fertigation, so you can dose different benches, blocks or greenhouses from one unit.
Talk to us about your fertigation system
Dosing Systems Australasia can size an injector to your flow, pressure and recipe, and supply the Twist II Clean filter to protect it. To see the full agricultural range, or to request a quote, visit our agriculture and irrigation page or contact our team for a recommendation.
This article is general guidance only. Always follow the fertiliser and chemical product labels, and confirm plumbing and backflow requirements with your local authority.
