Cover Crops & Green Manures Are Important Gardening Techniques That Have Many Benefits. But I’m Often Asked How To Kill Cover Crops Without Chemicals Or Cultivation. Here’s How.

Cover crops are an important gardening technique and I explain what they are in another post. Once grown the next question is how to safely kill them. There are many ways to kill cover crops without chemicals or cultivation. Each of them uses nature and natural processes to achieve control of the cover crop at the end of its useful life.

Mowing & Smothering Cover Crops

Green manures include the use of crops such as clover. The Secret is Often About How To Kill Cover Crops After Use
Green manuring and cover cropping include the use of crops such as clover.

One method is to mow the cover crop down to a height of 2-3 inches and then cover it with a thick layer of mulch, such as straw or wood chips. This will deprive the cover crop of sunlight and moisture, causing it to die.

In our food forest we killed off the grass … growing in much the same way as a cover crop .. by just smothering it in 6 inches of woodchip.

How To Kill Cover Crops By Crimping The Crop

Another method is to “crimp” or roll the cover crop. This will damage the stems and leaves and prevent it from growing.

Sunlight & Intense Heat Kills

You can also use the solar technique. This involves covering the cover crop with a plastic, or on a small scale, a glass cover and allowing the sun to heat up the crop and perhaps even the soil. The heat will kill the cover crop and any weed seeds that are present on the soil surface. On a small scale using a double glazed window placed on the soil works extremely well.

Pulling The Crop

Pulling the crop works well in some cases. Again it is better where the area is small and, in this case, the plants large.

The Hot Water Technique

If you lay a long black house in the sun for a while the water inside gets extremely hot. Squirt it onto living plants and it quickly kills them. I’ve actually used the method on my nursery to kill weeds growing around my greenhouses. I would join several long hose together to get a good volume of water heated in the midday sun and spray down any seedlings and small plants growing around the outside edge of the greenhouse. They would immediately scorch, shrivel and die. It took seconds!

The great thing is this is chemical free and relies on the sun to heat the water .. so is free.

How To Kill Cover Crops with Natural Senescence

Finally, you can simply let the cover crop die naturally. This will take longer than the other methods, but it is the most hands-off approach. For example a cover crop such as buckwheat is susceptible to frost. The frost will kill it and you are then left with a clear patch.

Here is a summary of how to kill green manure crops without chemicals or cultivation:

  • Cut or mow the crop. This will deprive the plants of sunlight and help to stop them from growing. Be sure to cut the plants down to a short height, about 2-3 inches or even shorter if you can. .
  • Smother the crop with a thick layer of mulch. This could be done with leaves, straw,wood chips, or even black plastic sheeting. The mulch will block out the sunlight and prevent the plants from growing.
  • Solarise the crop. As described above this involves covering the crop with something such as a black sheet that will heat up. The heat from the sun will then be trapped under the cover and kill the plants. Obviously this method is best used during the summer months when the sun is strongest.
  • Roll the crop. This method is best for smaller crops. Use a heavy roller to roll over the crop, flattening it to the ground. This will crush the plants and help to kill them. It’s not always perfect and might need doing several times, or combined with another method.
  • Graze the crop. If you have livestock, you can allow them to graze on the green manure crop. This will help to kill the plants and feed the soil at the same time.

It is important to note that some of these methods will take time to work. It may take several weeks or even months for the green manure crop to completely die off. Be patient and keep an eye on the crop to make sure that it is dying off as expected.

Here are some additional tips:

  • Mow the crop before it flowers or goes to seed. This will prevent the plants from spreading seeds and reproducing.
  • If you are using mulch, be sure to apply it in a thick layer, at least 6 inches deep.
  • If you are solarising the crop, be sure to weigh down the edges of the plastic sheet to prevent it from blowing away.

With a little patience and effort, you can kill green manure crops without using chemicals or cultivation.

Tag: How To Kill Cover Crops

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