How Much Atrazine per Gallon of Water

Atrazine is an effective herbicide widely used on crops to control weeds. It’s also used on lawns to prevent annual weeds. Learning how to use the herbicide is essential as the manufacturer recommends specific dilution rates for atrazine to be effective. But

how much atrazine per gallon of water is necessary?

According to the manufacturer, you should apply atrazine at a rate of 1.5 fl. oz per 1000 square feet in a gallon of water and 4.3 fl ozs of atrazine per gallon of water for each 500 square foot area. 

Read on to learn more about the correct application rate and the methods used to apply atrazine. 

How Much Atrazine Should You Use Per Gallon of Water?

To determine the amount of atrazine needed, you need to figure out the treatment area, which is the square footage that needs to be treated. You’ll need to multiply the length and width of the area in feet to get the square footage. 

Atrazine is considered effective when mixed at 4 ⅓ ounces per gallon of water to treat a 500 sq. ft of lawn.  However, it’s best to follow the manufacturer’s specifications and mix according to the requirements depending on your square footage.

Remember that there are different products containing atrazine, and the mixing instructions may differ from one brand to another. Still, a gallon of water and atrazine mix is enough to cover 500 sq. ft of space without affecting your grass. When mixing, always start by pouring the atrazine in the container, followed by the water. 

Using too much atrazine can harm other beneficial grasses. Avoid mixing atrazine with other chemicals, herbicides, or increasing the herbicide content per gallon of water. 

What is Atrazine Used For?

Atrazine is a post-, and pre-emergent herbicide used to control broadleaf and grass weeds in cornfields, turfs, and sugarcane fields. It’s categorized as an artificial systemic herbicide, also known as triazines. The atrazine can kill emerged weeds from the root system or kill weeds as seeds. 

Products that contain atrazine can be used for sorghum, corn, sugarcane, and guava.  There are over 300 products with atrazine in liquids, granules, sprays, or concentrates. 

You can mix, measure, and apply the herbicide in various ways to prevent weeds from taking over your crops. A backpack sprayer or handheld pump sprayer is recommended when using atrazine on your lawn. 

How Does Atrazine Work?

Atrazine affects the photosynthesis process in some grasses and broadleaf plants and is taken up by the roots and leaves. It then moves upwards in the new growth areas. The plant dries out and falls. You’ll notice that fresh leaves aren’t as affected as old leaves. Worth noting is that root growth isn’t affected by this herbicide. 

Atrazine takes 14-21 days to kill weeds

Applying Atrazine to Your Lawn

You need to apply atrazine to your lawn with a backpack sprayer or pump sprayer. Some sprayers have metering controls to allow you to mix the herbicide per gallon of water. 

Atrazine is a chemical, and you need to know how to handle it safely.  Here are some steps on how and when to spread it. 

Preparing Atrazine

Atrazine is available in a concentrated form, which means you need to dilute it to avoid overloading the grass. Follow the instructions on the product label, depending on your lawn size. For example, when handling a 500 sq. ft area, you’ll need 4.3 fl. oz of atrazine for every gallon of water.

Don’t mix the herbicide with another chemical as atrazine in itself is a surfactant product.  That means it should do the job on its own. 

Weather Conditions

The weather determines when to apply atrazine to your lawn. You should spread the herbicide when the temperature is between 60 degrees to 90 degrees Fahrenheit. Avoid using the herbicide when the temperature is over 90 degrees, as it will affect the weed killer’s effectiveness.

Avoid applying atrazine when the ground is wet or overwatered, as this also makes it less effective. 

Applying Atrazine 

Start by wearing protective gear, as any direct contact with the herbicide can be dangerous. Remember, your focus is on the broadleaf or grass weeds. 

Use a sprayer to spread the diluted atrazine mix. Spray the herbicide when temperatures are between 60-90 degrees Fahrenheit and on a day with no or low wind.

Once you’ve applied atrazine, you won’t need to water it in. you’ll have to wait until seven days have passed for you to water the area. It’s recommended to spray the herbicide twice a year to control the weeds.

Experts recommend putting in the first application in January to ensure weeds don’t have time to sprout after winter. You should make the second application when the harvest is done, which is around November.

Note that some places have a short growing season, you may have to wait to make the second application after the harvest time is over. The first application will have to wait until the snow has cleared off the ground. 

How Long Does Atrazine Last?

Atrazine can last for some days to a few months after it’s been applied, depending on the concentration. The herbicide is present in the ground for one growing season, after which it’s broken down. 

Is Atrazine Safe?

Atrazine is considered safe for use on some grass species like Zoysia, St. Augustine, and Centipede grass. You should avoid using atrazine on Fescue, Buffalo grass, Ryegrass, Bermuda grass, or Bentgrass.  Read the product label to ensure that the product is safe for use on the weeds you’re targeting. 

There are no studies conducted to prove that atrazine is harmful to humans. However, the chemical may be dangerous to animals like birds and bees. Avoid using atrazine in areas where your pets like to spend their time and keep them away from treated areas until the place is dry. 


Keeping your lawn weed-free can be challenging and tedious, but you can control the annoying weeds with the right product. Atrazine as a controlled-use herbicide can be useful for broad-leaf and annual weeds. You only need to follow the instructions when mixing it and wear protective gear when spraying it on your lawn. 

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