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Automatic Fertilizing with Drip Irrigation

Why fertilize with drip?

Drip irrigation delivers an exact amount of water to the roots of plants. If we add fertilizer to that water, we can deliver nutrients directly to the roots at the same time.

No waste, we deliver just enough fertilizer to meet each plants needs.

When we use the old method of broadcasting dry granular fertilizer on the surface of a garden bed, we depend on rain or sprinklers to wet the fertilizer. When the fertilizer dissolves, the plants are often overwhelmed with more nutrient than they can absorb, and the excess is washed off the field into waterways or ground water and becomes a pollutant.


A tank holds the liquid or dry fertilizer


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Compare two sizes of tanks

High rate of dilution

In contrast, an automatic fertilizing system can be adjusted to a very dilute ratio of fertilizer and water, up to 1000:1, so that a very small amount of fertilizer reaches the plants, just enough for their needs and no more. Your system is environmentally friendly and reduces the amount of fertilizer required.

The system can also be stopped and started at any time to ensure that your plants receive exactly the right amount of fertililizer.

The parts

An automatic fertilizing system available from our online store (Fertilizing units) consists of a tank to hold the fertilizer, a control valve built into the tank cap, and tubing to connect to your drip irrigation faucet assembly.

Any dry or liquid fertilizer can be used as long as it is totally water-soluble, with no small particles that may clog filters or drippers. Both organic and synthetic fertililizers are suitable.

The only difference in the two kits we offer is the size of the tank. The larger tank will hold up to 15 pounds of dry fertilizer and will cover up to 17000 square feet in one filling. The smaller tank holds 5 pounds of fertilizer and covers up to 5000 square feet.

A connector with hose threads is included so that it takes only minutes to attach to an existing drip irrigation system.


Safety concerns

Fertilizer solution must never be allowed to flow back through the faucet and into your domestic water supply.

To keep your domestic water safe, add an anti-syphon valve (V4) to the faucet before attaching the fertilizing system connector. That way, if there is a sudden loss of pressure in your domestic water supply, the water/fertilizer solution cannot syphon back through the faucet. Consult local bylaws for requirements.


If your drip irrigation system extends to ground that is higher than the faucet assembly, special precautions must be taken to prevent the backflow of irrigation water into your domestic water supply. Please consult a licensed plumber who can install a one-way valve that will keep your house water safe.

To install

Loosen the blue and green nuts on the side of the cap but do not remove. Push the end of the clear tubing into the hole in the green nut and tighten the nut. Do the same with the black tubing into the blue nut. Install the other ends of the tubing to the white hose bib adapter shipped with your fertilizer unit - the black tubing to the blue fitting and the clear tubing to the green fitting.

Install the white hose bib adapter to the faucet assembly below any filter, pressure regulator or timer. The fertilizer unit hose bib adapter should be the last component in any configuration.

Cut each length of clear and black tubing supplied with your fertilizer unit about 12" from the tank and install one small black valve, included, in each length of tubing. Turn the valve handles so the arrow is lined up with the tubing to open.

If you have a multi-station AC valve controller and system, we have a special connector, the FER4, to add an automatic fertilizing system. It's made of schedule 40 PVC and equipped with 1" female pipe threads that fit directly into a multi-station manifold system. The adaptor must always be installed downstream of the AC valve so that the tank is not under constant pressure.


To operate

The tank must be located at a height within 12 inches vertical of the faucet connector. Use a stand if necessary.

Add about two inches of water to the tank. Add the prescribed amount of dry water-soluble fertilizer or liquid concentrate. Open the small valves that control the flow of water to and from the tank and turn on the water.

The tank will fill with water and fertilizer solution will start to flow. Control the rate of dilution with the dial on the tank cap. The fertilizer will flow until depleted. Then clean water will fill the tank.

When done fertilizing, shut the two small valves to isolate the tank from the drip system. Now you can remove the tank from the cap and refill with fertilizer.

Any amount of fertilizer can be used up to the prescribed maximum, so that you can use a small amount of fertilizer for a small area of garden.

A special connector is available with a built-in valve (FER12). Use this connector if your drip system is operating at a very low water volume, down to 3 gallons per hour. Or if your drip system is higher than the fertilizing unit in elevation.




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