As the dominant species today, we’ve been able to reshape the very Earth we live in—controlling crop yield, plant aesthetics, and even weed overgrowth. However, it’s still pretty commonplace for some gardeners to wonder about waiting periods after applying herbicides to the soil.
You can till the soil between 30 minutes to four months after spraying the weeds in your garden. The actual wait time after application depends on the herbicide you use, its concentration, as well as the weather in your area. However, the way you apply the herbicide can also affect this period.
I recommend you check the manufacturer’s instructions on the herbicide packaging to ensure you have the correct time to work on your garden after spraying it. Still, knowing how herbicides work and how long they stay in the soil can help you make more informed decisions about weed spraying. Keep reading to learn how to spray the weeds in your garden, as well as practical tips about removing excess herbicides from the soil.
How Long Do Herbicides Stay In The Soil?
Weed killers are—without a doubt—beneficial substances, and they’re essential in gardening as well as commercial agriculture.
They’re one of the most popular ways to deal with unwanted plants and weed overgrowth, mainly because they’re easy to apply with effects that linger in the soil afterward.
Most herbicides stay in the soil for up to two weeks after you spray them in your garden. During that period, they evaporate and break down primarily into harmless compounds that might even benefit your soil in the long run.
However, the two-week period is an average figure. The actual time it takes for a herbicide to break down depends on the active ingredient in the weed killer, the soil you use it on, and weather conditions like rain.
Another critical factor that might affect this time is the amount of herbicide you used in the first place.
These factors can reduce the breakdown period, known as the Soil Residual Life, to as little as 24 hours. However, there have been reports that some herbicides can stay in the soil for up to several years after you spray them.
How Do Weed Killers Work?
But what gives herbicides their superpowers, and how can they effectively control plant populations? How can they work so fast, kill efficiently, and require almost zero effort?
Well, it turns out that the secret is a special compound called glyphosate. It’s a potent and non-selective weed killer that works by targeting and disrupting the metabolic processes of plants it comes into contact with—no matter how hardy they might be.
In fact, the compound is present in most of the weed killers on the market today. But how exactly does it work?
Plants rely on their root systems for many essential tasks, from support to nutrient absorption and even moisture uptake. Glyphosate gets into plant cells through these roots after you spray a weed killer on your soil.
It then spreads through the entire plant, attacking crucial enzymes in charge of photosynthesis and stripping the plant of the ability to perform the life-sustaining process.
However, glyphosate can also work just as effectively if it comes in direct contact with a plant. The effects are usually the same, but it might work relatively faster.
And while glyphosate isn’t the only weed killer in use today, others—like paraquat—work in pretty much the same way.
Are Weed Killers Harmful?
Now that we have a basic understanding of how herbicides work and how long they can stay in the soil, it’s time to answer a critical question. Are herbicides harmful to plants, animals, or humans?
Well, herbicides are essentially poisons. They’re incredibly toxic chemicals designed to kill quickly and efficiently. However, herbicide manufacturers are required by law to develop their products to specific standards.
These standards help ensure the product works just as well as intended but with minimal risk to animals, humans, and plants. Therefore, most weed killers should have little to no effects after evaporating or breaking down in the soil—typically two weeks after you spray your garden.
However, as I mentioned before, it’s not uncommon to find traces of herbicides in the soil long after you sprayed the area. But these are usually more potent products designed to work for extended periods.
These long-lasting herbicides are usually not found in open markets, and you’ll need a license to get one. Still, their effects can be pretty diverse and life-threatening.
Ultimately, you should stick to regular herbicides like the Roundup Ready-To-Use Weed & Grass Killer III (available on Amazon.com) if you want to spray weeds in your garden. This product is practical, easy to use, and will break down in less than two weeks.
Ensure you read the manufacturer’s instructions before using the weed killer in your garden, and wear any necessary safety equipment before handling the chemical.
How Do You Remove Herbicides From the Soil?
You might have situations where you accidentally sprayed too much herbicides on your soil to kill weeds, and you need to reduce them. Or maybe you’d like to cut down the soil residual life and start tilling the ground as soon as possible. Well, there are ways to remove herbicides from your soil for whatever reason you might have.
You can remove herbicides from the soil using any of the following methods:
- Leave the soil alone for some time.
- Till and fertilize the soil.
- Grow some cover crops.
- Use soil additives.
Herbicides remove the need to use excess effort when controlling weeds, and I almost always recommend them to my friends and family.
The methods in this section will help you deal with any situation where you might have gone a little overboard. However, they can also work in less dramatic cases. Let’s explore them in more detail.
Leave the Soil Alone for Some Time
Doing nothing is a fantastic way to remove herbicides from the soil. All chemical compounds break down after some time, even weed killers, and your soil should be free of all product traces in a few weeks.
This method is inexpensive and easy but might be very time-consuming and unreliable. After all, the rate of herbicide decomposition depends on several factors. Therefore, you might need to wait a few weeks to several years to remove the compounds from your soil altogether.
However, leaving the soil alone for some time doesn’t necessarily mean you can’t use the soil for that period. You could plant some non-susceptible species in the area or install some aesthetic pieces until the ground is herbicide-free.
Till and Fertilize the Soil
Another great way to remove herbicides from your soil is to till and fertilize the soil. These might seem like unconventional practices, but they’re pretty effective. Microorganisms are responsible for compound degradation and herbicide decomposition.
They work by using the active ingredients in weed killers for their metabolic processes, releasing beneficial compounds as by-products. Tilling and fertilizing can help improve the environmental conditions of the soil, improving microorganism growth and reproduction.
But how exactly does tilling help? Most microorganisms seem elusive but need water, air, and nutrients like every other species.
Tilling can help improve the oxygen content of the area, just like fertilization increases the concentration of essential nutrients in the soil. Of course, you’ll need to water it to ensure the microorganisms thrive.
This method might require some work, but it’s inexpensive and results in a healthier garden. You can also use compost or other organic matter as fertilizers for the soil—but ensure you don’t use too much.
Grow Some Cover Crops
You can also grow cover crops to remove weed killers from the soil in your garden. This method is similar to leaving your soil alone for a while—since it takes a bit of time to work—but is faster and more efficient.
All you need to do is plant cover crops in the affected areas and leave them to thrive. These plants will draw up the herbicide compounds as they grow, remediating the soil.
This process is known as bioaccumulation and works for other substances like fertilizers and radiation. However, you’ll need to dispose of the plants afterward since they’ll be contaminated with herbicides.
Some examples of cover crops you can use to remove herbicides from the soil include:
- Sunflowers
- Corn
- Peas
- Oats
These plants are relatively easy to grow and manage, and they should remove the herbicides at the end of the growing season. Remember to correctly dispose of them, as using them as compost or fertilizer can recontaminate the soil.
Use Soil Additives
You can also remove herbicides from your soil by using soil additives to deactivate the active ingredients in the products. These additives bind to the herbicide compounds before they attack plant enzymes, rendering them useless.
An excellent soil additive you can use is charcoal, but any other carbon-rich alternative will work just as well. The additives are pretty inexpensive and easy to apply, but their effects might linger for some time. Therefore, I don’t recommend using soil additives if you plan on spraying weeds in your garden frequently.
Conclusion
You can till the soil between 30 minutes to four months after spraying the weeds in your garden—but the herbicides could linger on in the ground for years after use. However, this soil residual life might not always be harmful to you or your plants.
Fortunately, you can remove herbicides in your soil or minimize their levels using any of the methods I highlighted in this article. Always take proper precautions when working with herbicides and read the manufacturer’s instructions before use.
