# Calculating fertilizer mixing ratios for garden hose sprayer.

roflwtime(7a)April 29, 2014

Hey gardeners!

I know I see people discussing mixing ammonium sulfate into gallons of water, but I was wondering if anyone uses one of those garden hose sprayers that has a canister attached to it which is used for fertilizing or weed killing.

I ask this because hauling buckets of water to every plant is a lot of work and it would be nice to just hook up a sprayer and go to town on the plants. It would save me some time and possibly my back.

The sprayer I bought has a canister that can be filled up to 32oz of some solution.

Unfortunately, the lowest setting it can be set to is to use 1 1/2 tsp of solution per gallon of water sprayed. That flow rate is pretty high and adding a concentrated dose of ammonium sulfate to the canister can easily kill your plants.

Here is my thinking in order to get a dilution of say 1/3tsp of ammonium sulfate per gallon:

There are 768 teaspoons in a gallon. I want to spray at a 1: 768 x 3 = 2304:1 ratio per gallon, but my sprayer only sprays at a (1 / 1.5) x 768 = 512:1 ratio per gallon.

Therefore, my ratio is 2304:512, which is 4.5 teaspoons of water per 1 teaspoon ammonium sulfate.

As I said before, my canister is 32oz. There are 192 teaspoons in 32oz of water, so 192 / 4.5 = 42.6667 teaspoons of ammonium sulfate or 14.2 tablespoons.

In conclusion, I would add 32oz of water to the cannister and mix up 14.2 tablespoons of ammonium sulfate to give me the 1/3 tsp per gallon rate to fertilize with.

Does my math seem correct? I want to make sure I am right!

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fruitnut Z7 4500ft SW TX

My concern would be how accurate and linear is the dosage applied. I'd expect more applied early and less late. But I only tried one a couple times and it's hard to know what you're actually applying.

April 29, 2014 at 10:24PM
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roflwtime(7a)

Fruitnut,

I may spray in a 10 gallon bucket and measure and see if 1.5 X 10 teaspoons of water was actually removed from the cannister.

April 29, 2014 at 10:32PM
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Those siphon mixers output can vary with water pressure but not a great big amount. You can always divide it up and make two or even three applications to be sure you don't mess up. Comercial users use an injector that can be very accurate.

This post was edited by kyyada on Wed, Apr 30, 14 at 19:54

April 30, 2014 at 7:53PM
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