It takes a lot of time and effort to fertilize a garden by hand. Luckily, there’s a simple and effective way to let your drip system do that work for you. Enter the fertilizer injector! In this article we will discuss how fertilizer injectors work and give you some tips on how to choose the right one for your garden.

Why Use a Fertilizer Injector?

A fertilizer injector is a tool that mixes liquid fertilizer with your irrigation water, delivering nutrients straight to your plants' roots.

  • Saves time: A fertilizer injector can do the work once your system is set up. No more hand-mixing or hauling heavy bags from plant to plant. Simply set it, connect it, and let it feed.
  • Direct Application: Your drip system is already set up to deliver water directly to your plants, so adding fertilizer to that water means it will go exactly where it’s needed too. That means no more worrying about missing plants or under/overfeeding different areas.
  • Cost-effective: Fertilizer is a lot more expensive than plain water, so every drop counts. Nutrients are absorbed where they’re needed, and water use stays low. This type of system minimizes waste, which can reduce your overall fertilizer costs. Over time, that can make a noticeable difference in your maintenance budget and your soil’s long-term health.

How Do Fertilizer Injectors Work?

Basically, all automated fertilizer injectors use water pressure to draw fertilizer from a tank and mix it with your irrigation water, resulting in a nutrient-rich solution that is sent straight to your plants' roots. How exactly water pressure is used for this purpose depends on the type of injector.

The Different Types of Fertilizer Injectors

Liquid fertilizer is a liquid, which means that any principle that you can use to put water into a drip system can also be used to put liquid fertilizer into one. That being said, there are two main types of fertilizer injectors that you’ll see used for home garden or landscape purposes. The DIG Add It Fertilizer Injectors that we sell work on this principle.

Venturi Fertilizer Injectors

Venturi injectors are the simplest and least expensive type of fertilizer injector. They introduce a bottleneck at the point where your plain water flow touches your liquid fertilizer. This bottleneck creates a pressure differential that draws liquid fertilizer up into the flow of water.

Pros: Venturi injectors are straightforward and economical. Since they have no moving parts, they tend to be quite reliable. Plus, they don't need external power; they simply use your irrigation system's water pressure to operate.

Cons: Their flow rates can be somewhat limited, making them best suited for smaller to medium-sized watering systems. They also might not be as precise as other types, particularly when dealing with larger systems. Lastly, venturi injectors are limited by the size of their tank.

Best For: These are a great choice for small to medium garden beds or if you're working with a limited budget. They're perfect for home gardeners who want an affordable and simple way to fertilize their plants.

Piston or Diaphragm Fertilizer Injectors

Where a Venturi-style injector relies on the passive interactions between two liquids, piston or diaphragm injectors are much more active. They use water pressure (or electricity, which is often the case with diaphragm injectors) to move a mechanism that draws liquid fertilizer from a tank and injects it into the flow of water. They operate like small pumps, taking liquid from one place and actively putting it into another. We carry a large selection of Dosatron fertilizer injectors, which include both the standard piston-driven doser units and the more advanced Etratron diaphragm-driven injectors.

Pros: These are much more precise than Venturi injectors, as you can readily adjust the injection rate with a dial, button, or knob. They’re often built to handle much higher flow rates than Venturi injectors or to offer extreme levels of control over the injection rate. Lastly, they are more flexible when using multi-part fertilizer recipes, which can be difficult to do correctly with Venturi injectors.

Cons: The main con is price, which is significantly more than a venturi injector depending on the size. They also involve a number of moving parts, which means more maintenance is required to keep them in good working condition.

Best For: These are a good fit for larger gardens of landscapes, or for commercial settings such as a nursery or greenhouse. They’re also idea for any setting in which you want fine control over your fertilizer delivery, as changing injection rates is very easy.

Choosing the Right Fertilizer Injector for Your System

System Size and Flow Rate

Your irrigation system’s size and water flow rate should be the starting point. Venturi injectors tend to be mounted directly to their fertilizer supply tank, and the system will need to be turned off to refill the tank. This is why all the Venturi injectors we sell have a “gallons to empty” spec (see page 2 of the linked document) which describes how many gallons of water can flow through the injector before it has used all its available fertilizer. If you have a large garden, it may be more trouble than it’s worth to use a venturi injector with a small tank that you’ll need to refill every 5 minutes of runtime.

Fertilizer Type

Not all fertilizers are created equal, and some work better with specific injectors. Liquid fertilizers are the most common, but you’ll want to make sure your injector is compatible with the type you’re using. All injectors need liquid fertilizer, but venturi injectors work best with fertilizer that comes as a liquid, while piston or diaphragm injectors can handle fertilizer with more particulate matter in it. Remember that even if your injector will work with a particular fertilizer, you should still ensure that it is safe to run through your drip system.

Budget Considerations

Cost is always a factor. Sure, a high-end model comes with advanced features, but a basic, reliable injector may be all you need for smaller gardens or lawns. Consider what fits best within your budget without sacrificing performance. There’s no good reason to buy a $1000 Dosatron injector for your pair of backyard raised beds.

Compatibility with Your Irrigation Setup

Pick an injector compatible with your irrigation system. Trying to fit a 1.5” Dosatron injector onto a ½” poly line is just as much of a pain in the neck as trying to fertilize a large nursery with 1-gallon Venturi injectors. This is exactly the kind of thing that we can help you with! Give us a call at 877-597-1669, email us, or schedule a consultation today!

Find What You Need at the Drip Store

Visit our blog for practical tips on feeding and watering your garden efficiently. Shop our wide range of fertilizer injectors, drip irrigation kits, and essential parts to build the perfect system for your garden. Need guidance? Call us today or book here to schedule a free consultation with one of our experts.