Automated Fertilizing Systems for Your Greenhouse


You will enjoy your DIY Greenhouse much more if you keep the number of boring chores to the minimum. Since watering and fertilizing are the most time-consuming tasks you have to do in the greenhouse, it makes sense to try and automate a system to do both. Fortunately, once you install a good automatic watering system you are half-done with automating a fertilizing system as well.

The most efficient way of distributing fertilizer to your greenhouse plants is to do it together with water. For example, your drip irrigation system delivers water directly to the roots of plants. If you add fertilizer to that water, nutrients will also go directly to the plants’ roots. And the best thing is: there is no waste. Each plant gets just enough fertilizer to meet its needs, which can be adjusted by controlling your watering system.

Depending on how often you want to fertilize your greenhouse plants, an automatic fertilizing system can be regulated to deliver a diluted ratio of fertilizer and water, up to 1000:1. The more often you fertilize, the weaker the ratio of fertilizer in the water should be. If separated; the fertilizer delivery system is connected to the water supply only when you wish to fertilizer plants. You can stop it and start it whenever you need it.

Drip irrigation system is the most suitable system to be used in conjunction with an automatic dispenser for fertilizer. There are two basic automatic fertilizing systems for the average DIYer: siphoned and injected.

Siphoned Type System

The siphon type system resembles a double fitting for a hose, where one end is connected to the water source, and other, through a pipe, to the container with fertilizer. The container can be a bucket in which you poured a concentrated water-soluble fertilizer, or the syphon system may come with its own container, with already pre-mixed water-fertilizer solution. When you turn the water on, fertilizer gets sucked from the container and delivered to plants through the irrigation system, resulting in a diluted solution before reaching your plants.

Injector Type System

Injectors may also be connected to the water supply going to an irrigation system, such as drip system, though they use a pump to add fertilizer to the water stream rather than relying on pressure difference like the siphon type systems do. Some types of injectors come with a cartridge of concentrated fertilizer, which enable the user to have control of the percentage of fertilizer per gallon of water delivered to the water system.

Users must always keep in mind that your fertilizing system is connected to your water supply. You cannot allow fertilizer solution to flow back into your domestic water supply if your greenhouse is tied to the same water supply as your home. In order to prevent this contamination you need to install an anti-syphon valve or a back-flow preventer to keep your water safe for human use. You can find these at any home improvement store, or through our online store.

Another safety feature is a flush valve, which is a valve that will open after a water cycle is complete either manually or automatically. After delivering fertilizer to your plants, you should flush your water system of any chemical residue, which can accumulate on the water pipes and nozzles – such accumulation may cause issues with water flow or even potential corrosion of pipes and fittings.

Always make sure that the soil in your pots and trays is wet before or during the time that you start distributing fertilizer. You should never add dry chemical fertilizer to plants, as you can seriously damage them that way.

If the excess water with fertilizer runs out of your pots and trays, you should also add or make catchment trays to prevent fertilizer from running out of the greenhouse and potentially damaging the water table or other ground level water supplies. Nutrients in fertilizer can damage a natural ecosystem and affect both plants and animals alike (they are infamous for causing algae blooms.)

Fertilizer Types

For your automatic fertilizing system to be efficient, you have to use a completely water-soluble fertilizer. Check the label on the product you want to use. You can use either dry (powder) or liquid fertilizer, as long as it does not have any small particles, which can clog the water drippers of your irrigation system. You can use organic fertilizer as well, but make sure that all small particles have been filtered or screened out.

The general rule of thumb is to fertilize your greenhouse plants once a month, but it really depends on the kind of plants you grow. You might prefer to fertilize more often, especially your blooming annuals, but in that case you have to deliver a much more diluted concentration of fertilizer.

Occasionally flush your pots and trays with water, to prevent accumulation of salts in the soil.

Once your automatic fertilizing system is in place, your job is not completely done. Each plant you grow has different needs and you need to learn about what, and how often you should feed them. While most greenhouse plants will do well with a balanced, but heavy on nitrogen fertilizer, flowering and fruiting plants have different needs. Some flowering plants like azaleas should not be fertilized while in bloom. In fact, you will have to learn about the habits and needs of every single plant in your DIY greenhouse, just like you do with pets in order to ensure a successful growing season.

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