How To Calibrate Liquid Fertilizer & Herbicide Applications

I’ve watched and read lots of articles and videos on how to properly calibrate your backpack sprayer.

There is some great info out there, but in my opinion, over-complicated.

The most important aspect of calculating application rates (no matter what the product) is knowing your property size.

I strongly suggest using this website and printing out a map of your property.

Here is a map of my property:

I typically round my “sections” to the nearest 500 feet. So I would round my front yard off to 4,000 feet and my backyard to 7,500. I have a few tree and other objects so I subtract a little for those.

Applications are almost always calculated on product per 1,000 square feet.

When you are spraying, you use a “carrier” to put down the product. Most of the time the carrier is water.

If the product you are using states to put down 1 ounce per 1000 square feet, you can’t actually put down 1 ounce, you need to mix it with a carrier – such a water. The water helps to “carry” the application product to the desired location.

How Do I Figure Out How Much To Spray?

Pretty simple.

If the product I am applying has a rate of 2 ounces per 1,000 square feet, I fill my backpack sprayer up with 8 ounces of product and then add in water until I hit the 4 gallon mark.

That will give me enough for 4,000 square feet of property.

See how I did that?

So now I know I need to walk around my front yard until my backpack sprayer is empty. That will get me very close to the 2 ounces per 1,000 rate that I want.

I typically walk around the edge of the area that I want to do first, at a good pace, not running but just a slightly faster than normal walk. I then walk back and forth inside the area I just sprayed until I have covered all the property. I almost always have extra product in my tank.

I then walk around the entire space fairly quickly (making sure to avoid over spray) and try to put the rest of the application down as uniform as possible.

Also, the more carrier (water) you use in your tank, the more wiggle room you have for error since the concentrate won’t be as strong.

This can be a confusing topic and scares people away from spraying, but once you get the hang of it, it’s really enjoyable!

Please let me know if you have any questions – send me an email or leave a comment below.