PLANTS THAT PRODUCE

Plants That Produce

Fertigation: Hose-end Sprayers & Irrigation Injection

By Richard Frost

Hose-end sprayers are a popular way to apply liquid fertilizers and liquid insect controls. It is very important that you obtain a proportional sprayer and get rid of any non-proportional sprayers you might own. Of these, the Miracle-Groâ brand sprayers are the worst. The design causes 50% of the fertilizer to be delivered to the first 7% of the plants and the rest get a rapidly diminishing amount of colored water. Instead, obtain a proportional sprayer such as the Gilmore or Dial-N-Spray brands. The vessel on the Gilmore brand isn’t threaded very well, so the Dial-N-Spray gets my highest rating. Of course the best thing about the Dial-N-Spray is that the original design was done by SDHS member Ronald Wheeler!

When fertilizer is applied to plants in liquid form by overhead spray we call it foliar feeding. This should be done in the early morning when dew is present – or at least when dew would be present during a non-arid season of the year. This time of day is when plants typically have their pores open for intake. In contrast, pest controls should be applied in the late afternoon when the bees have left the plants and are on their way home to the hive.

The injection of fertilizer into irrigation lines is called fertigation. This is not a new practice: I recall nitrogen gas being injected into row irrigation column heads (cement canisters) for citrus in the 1950’s. Nowadays there are two popular methods in use: siphon injectors and self-propelled pumps.

Here again the user needs to insure they have a proportional system. The most notorious of the non-proportional fertigation systems are sold under the name EZ-FLO. Recently I have noticed another system being marketed in the San Diego area under the GREEN-FLO brand. All of the non-proportional systems are easily identified as a unit that pushes a small amount of water into a canister which displaces a small portion of water-fertilizer mix into the main water flow. All dispensers of this design are non-proportional and deliver 50% of the original fertilizer in the first 7% to 10% of flow, and after that a very weak mixture.

Siphon injectors are inherently proportional and easy to use. Nearly every nursery in town stocks them. The only drawback is that at least 50 psi of water pressure is needed to “drive” the unit. Simply hook one up at your hose faucet or on the irrigation side of an electronic irrigation valve, drop the suction hose into a 5-gallon bucket and you are ready to start dispensing a water-soluble fertilizer. If you choose a water-soluble fertilizer made from natural minerals and plant oil chelate, then this is the most cost-effective, environmentally responsible, and easiest way to feed plants on a modest size property.

For those of you who have low water pressure, or a larger property, or just a huge number of plants (chagrin), then the Dosatronâ water-driven injectors are the method of choice. The units range in size from a small handcart with wheels to a very large system for commercial agriculture. Dosatron is not the only manufacturer of water-driven pumps but they do have the best record in maintenance and longevity. Crop Production Services in San Marcos typically has the lowest prices but you may want to check with other suppliers too.

SDHS member Richard Frost is a certified edible gardening nut. For copies of past articles and more information, please see www.PlantsThatProduce.com.

Reprinted with permission from June 2010 "Let's Talk Plants," the newsletter of the San Diego Horticultural Society, www.sdhortsoc.org