Can Too Much Compost Kill Plants?


Wooden Compost Bin Next to Bush

Compost is known to be one of the most beneficial solutions when you’re growing plants at home. It’s relatively affordable, especially if you’re using your own waste from around the house. However, some homeowners are worried about the effects of using compost too often or having an improper balance.

Unfortunately, too much compost can harm or even kill plants can. There are two reasons that compost can be bad for your soil:

  1. If you have an imbalance, you could provide too much of one nutrient and not enough of another.
  2. Too much compost on your plants can weigh them down or prevent them from absorbing naturally occurring nutrients in the soil.

Throughout this article, you’ll learn the importance of maintaining the correct balance for a good compost pile. You’ll also find the dangers of using too much compost, as well as how much compost you should spread around your garden.

Can You Have Too Much Organic Matter in Soil?

When you’re first beginning your journey of using compost material in your garden, it can be a bit overwhelming. You have to remember the composition of the organic matter, how much you’re supposed to use, and what you can and can’t throw in the pile. To make it even more confusing, you now know that too much can ruin your garden.

Don’t worry, though; It’s fairly easy to maintain your compost bin and soil once you have everything as it should be. As far as adding too much quantity of compost to your soil, the biggest concerns would be overweighing your garden’s roots and excessively high levels of phosphorus.

Phosphorus comes from your organic compost pile, but it can be dangerous when there’s too much of it. It soaks into the soil at an incredibly slow rate, sometimes taking multiple years to be fully absorbed. Unfortunately, it can be the bane of your garden by the time you see its effects.

The reason that phosphorus is so harmful is that it prevents your plants from absorbing other nutrients, most notably manganese and iron. Without those components, your plants can suffer from malnutrition and never grow properly. High amounts of phosphorus can be outright toxic to certain species of fungi as well.

If you’re able to break it down to a science, the top portion of the soil in your garden shouldn’t have more than 5% organic matter from your compost pile. It can be hard to be precise since there’s no real way to measure, but you can gauge it based on the depth of your seeds and roots from the garden.

Note: Manure produces much more phosphorus than plant-based organic matter. If you’re worried about having excessively high levels of phosphorus, steer clear of using manure for small gardens and trees.

How Much Compost Should I Put in My Garden?

Before you start adding compost to your garden, you need to know two things:

  1. What type of garden you have (annual or perennial)
  2. What kind of compost you’re using

If you’re using a manure-based compost, you can usually use a lot less. Manure is heavyweight and loaded with nutrients that are vital for the longevity and quality of your garden. However, it’s usually better when it’s used for farms. Since it can be packed with phosphorus as mentioned above, it’s crucial that you don’t overdo it.

Adding compost is not only important in quantity and quality but also the time of year that you add it. You shouldn’t constantly add compost matter; Otherwise, you’ll end up with too much. On the other hand, not adding enough compost will leave your garden without the proper nutrition to thrive in its environment.

Here’s a quick breakdown of how much plant-based compost material you should add to your garden:

  • For annual gardens filled with flowers and other plants that show up once a year, you should add compost during the spring when they’re growing the most. Spread about two inches of compost evenly over the garden, then follow it up by tilling the compost into the soil down to six inches below the surface.
  • For perennial gardens that have plants blooming and growing throughout the year, you should add compost at the same time each year. For example, if you added it in January, try to always add it during the same month next year and the following. Lightly till the soil after you’ve added one inch of compost and one inch of mulch.

Not all gardens respond the same to compost material. You can try to work around your own plants to see how they work with different compositions, but these guidelines will prevent you from ruining the plot. If you want precise measurements, try this online compost calculator.

What is the Perfect Compost Mixture?

There are two different types of materials that go into a compost pile or bin: Brown and green matter. Brown matter refers to materials that are dry, including wood chips, dry leaves, straw, or even things like brown paper bags. Green matter refers to materials that are still filled with water or life, such as grass clippings or food scraps.

Using the perfect mixture of brown and green matter in your compost bin is essential to its effectiveness. Incorrect balance can lead to the aforementioned concerns, or it can slow down the growth process. Fortunately, you’re in the right place to find the ideal combination.

Most experts suggest that you use a 4:1 ratio of brown:green matter in your compost bin. This means that you need to use four times as much newspaper, dead leaves, and other brown matter than you’d use grass clippings and food.

Brown matter is loaded with carbon, which is an essential component for all life across the planet. Without brown matter, your garden won’t ever start growing. Green matter is packed with nitrogen, which is another essential living component due to its ability to assist in the growth of proteins.

If you have too much brown material, your garden won’t absorb any green materials. On the other hand, too much green matter can cause your pile to smell horrific, stay overly moist and host bacteria, or kill your plants from excess nitrogen.

By using the 4:1 rule, you can create a perfect compost pile for your garden. Remember to regularly sift through the pile and stir it up with a rake to keep it filled with oxygen so it can decompose properly. Composting is a long process, but the results are more than worth the effort that you’ll put into it.

How Do You Fix a Bad Compost Mixture?

If you’ve found yourself with a compost pile that’s seemingly ruined, you can still fix it in due time. The most common problems of compost piles are almost always solved by fixing the brown:green ratio or adding oxygen to the pile by raking it. You can also use a composting tool, like this one found on Amazon to add oxygen.

Final Thoughts

Composting is supposed to be fun, creative, and eco-friendly. You can make one of the best gardens in the world right in your backyard. With the knowledge you’ve gained throughout this post, you’re fully equipped to start the process.

Here are a few takeaways from the article:

  • Too much compost is bad because it adds excess weight and phosphorus.
  • Maintaining a brown:green (carbon:nitrogen) ratio of 4:1 is essential.
  • The amount of compost you add depends on whether your garden is annual or perennial.
  • Manure has much more phosphorus than plant-based compost.

Anne James

Hi, I'm Anne but my grandchildren call me Jelly Grandma. I hope your visit here has been a sweet one.

Recent Content