Fertilizer Injectors

A fertilizer injector puts nutrient, acid or a cleaning solution into the irrigation line so every container, bench or bed is fed as it is watered. On a production nursery or greenhouse it replaces hand-mixing and lets one set of lines carry plain water on one cycle and feed on the next. The page runs from hose-end siphons to controller-managed dosing systems.

The decision that matters most is the flow range the injector will actually see. Every unit here is rated for a window of flow and pressure, and an injector run outside that window doses the wrong ratio no matter how carefully the stock tank was mixed.

Proportional injector, venturi, siphon or dosing system?

Start from how the operation waters, not from the catalog.

Houses that are hand-watered from a hose need feed at the hose end. Dramm's Syphonject is a 20:1 siphon rated at 40 psi that draws solution on the pressure drop of the passing stream, and the Ferticart range puts a stock tank on a cart built for a Dosatron injector, so feed moves between houses.

Zoned drip, spray-stake or overhead systems running one feed program are the home ground of the water-driven proportional injector. DEMA's MixRite TF-3 through TF-25 cover 0.8 gpm to 110 gpm on 1 inch to 2 inch NPT connections, with ratios from 0.2% to 2.5% depending on model. They are positive displacement, need no electricity, and hold the set ratio as flow changes inside their window. Amiad's hydraulic-motor injector pumps do the same job from line pressure, from 66 gal/h in the Fertilizer Injector Pump 4-01 and 4-02 / 4-92 to 132 gal/h in the Duplex Fertilizer Injector Pump 4-03.

Operations feeding several stock tanks, or holding EC and pH targets across many valves, move up to venturi and multi-channel dosing. Netafim's FertiOne Plus runs two venturi channels up to 158 gph, the FertiKit 3G draws fertilizer and acid through dosing channels on a booster pump, and the NetaFlex 3G handles 13 to 282 gpm of system flow. Heron Electric's dosing sits under a Heron controller, and Rivulis runs from basic venturi to fully automated with pH control.

What do the flow, pressure and water need to be?

Size the injector to the zones it feeds, not to the pump. Check the smallest and largest zones that will run through it against the unit's window. A MixRite TF-3 is rated 0.8 to 11 gpm; a TF-25 is rated 9 to 110 gpm. A propagation zone pulling less than 9 gpm through a TF-25 sits below its minimum and gets plain water. If the zone range is too wide for one unit, split the head end into two injectors or bypass the low-flow zones.

Pressure matters most for venturi systems, which need a differential across the venturi to pull solution. The FertiOne Plus is rated up to 80 psi on the mainline. The FertiKit 3G takes its differential from a booster pump, with two of its seven models built without one. The NetaFlex 3G works between 29 and 100 psi. Water-driven and hydraulic-motor injectors run on line pressure alone, which is why they suit remote blocks without power.

Put a screen or disc filter ahead of any injector. Pistons, needle valves and venturi throats are small passages, and grit from a pond or well will wear or block them. If the water carries high alkalinity, plan on acid dosing; Heron's pH Dosing Systems handle direct injection or circulating acidification of a storage tank. Keep stock solution fully dissolved and moving. Dramm's larger Ferticarts add agitation for this reason, and the 50-gallon models aerate the stock solution for nematode applications.

What goes wrong, and how do the lines differ?

The failures we see are rarely the injector itself.

• Sized to the pump. The injector is picked to match the head-end pump, and the small mist zone runs below its minimum and never sees feed. Size to the zones.
• No filter upstream. A season of pond water through an unfiltered piston or venturi ends in a rebuild.
• One tank for everything. Calcium sources mixed with phosphate or sulfate concentrates precipitate in the stock tank. Two-channel and multi-channel systems exist so those stay apart until they meet in the line.
• Set once, never checked. Injectors wear and stock tanks settle. Check EC at the emitter, not at the tank.
• Siphon on a long run. A hose-end siphon depends on the pressure drop of the water passing it; long hose and a throttled breaker change the draw.

The manufacturers here take different routes to the same job. DEMA builds simple, serviceable water-driven proportional injectors in four sizes. Netafim covers schedule 80 PVC venturi kits through to multi-channel dosing for larger operations. Heron Electric treats dosing as part of the controller, with booster-pump, feedback and buffer-tank options. Rivulis runs from basic venturi to fully automated systems with pH control. Dramm serves the hand-watering and cart end with the Syphonject and Ferticarts. Amiad's hydraulic-motor injector pumps run wherever there is water and no power. Send us your zone flows, water test and the number of stock tanks when you request a quote.