Compost Overload What You Need to Know Before You Apply More

Many gardeners opt to keep a compost pile in their yard due to concerns about using commercial fertilizers and chemicals on their growing gardens. Although compost’s benefits for a garden are undisputed, could there be such thing as too much of a good thing?

In this case, there is such a thing as too much Compost. Too much can harm the soil and plants, especially manure compost. But why? What is it about too much Compost that can be harmful to plants?

Wide range of benefits for plants and soil in a garden, from adding Compost

Adding Compost for Soil Fertility Improvement

Compost supplies plants with essential nutrients to grow because of its well-decomposed organic material. These nutrients include phosphorus, potassium, nitrogen, as well as micronutrients.

Checking compost with worms with bare hands

Soil Structure Improvement through adding Compost

A stable form of organic matter is added to the soil when Compost is added. As a result, the moisture-holding capacity is increased in the soil. The Compost can improve soil that has become compacted or is too sandy.

Adding Compost also aids in Soil Health Improvement.

Compost contains microorganisms that are beneficial to the soil. Nutrients will become more available to plants because of these microbes. In addition, when these beneficial organisms’ number and activity level dominate the soil’s environment, they also suppress their pathogens.

After reading this, you probably wonder, “Why wouldn’t I need more compost in my garden?” Of course, these benefits are great for any garden.

The answer does depend on what your lawn or garden needs. Different nutrient levels and soil types come with every garden – maybe even different pH levels.

Soil tests are always recommended to construct the best soil amendments for your yard and gardening goals.

A working garden will require water, plenty of sunshine, plant nutrients, good rooting soil, and good weed and disease control. But, when adding new plants to a garden bed, it can be not easy to know if you need Compost – or how much. So, let’s discuss what Compost is.

The video below shows you how to make nutrient-dense Compost that is perfect for adding to your garden soil. Watching this video will teach you everything you need to be successful every time.

What is Compost, and why should we add it to our soil?

Compost is something that many gardeners swear by because of the many benefits that it offers to their gardens. It is an organic matter of shredded twigs, leaves, plants, and kitchen scraps.

Instead of paying a company to clean up and haul away dead plant matter, composting is a great way to save money by recycling any yard waste that would have ended up in the landfill in plastic bags.

Gardeners boost their plants by giving them all the necessary nutrients to incorporate Compost into their gardening routine.

However, using too much Compost will harm plant growth or kill it. This is the unfortunate dark side of compost use.

The Dark Side of Adding too much Compost

As we know, adding Compost sounds like the best possible thing to add to any garden to add nutrients from the decomposed plant matter. Over time, plants will use the nutrients from the topsoil in the Garden or the planting pot, so adding Compost would be ideal, right? Well, that’s not always the case.

Yes, Compost adds nutrients to the soil, but Compost is not a fertilizer, as few gardeners will know. Unlike commercial fertilizers, Compost isn’t a ready-made form of adding energy back into plants.

Nutrients such as nitrogen and phosphorus are added to plants from Compost; however, uncured Compost can turn deadly.

Using uncured Compost of organic plant matter may be very tempting, but it will contain seven times more phosphorus than any plant would need. When too much phosphorus is absorbed, it becomes poisonous to a plant, even though smaller amounts of phosphorus are vital. The same can be said of Compost, which is made of manure.

Why Adding too much Compost Can Become Deadly To Plants.

Too much Compost can be poisonous due to higher phosphorus levels if the Compost is not fully cured, even though it can be a great source of nutrients and builds the structure of the soil.

High phosphorus levels will make it harder for plants to absorb iron and manganese; this will result in deficiencies causing chlorophyll in the plant leaves to leave the plant’s veins and be trapped on the outside. Too much iron or phosphorus can be the cause of this. You can add to this problem by adding more Compost and killing your plant.

Mycorrhizal fungi are vital to the plants’ microbiome; high phosphorus levels are toxic to mycorrhizal. These fungi supply the plant with water, phosphorus, and nutrients. Without it, plants must use more energy, which larger root systems need to survive.

The Four Stages of Compost and what happens to the soil when we add them

Compost goes through four curing phases before it becomes useful to gardeners for their Garden. These phases are:

  • The Mesophilic Phase
  • The Thermophilic Phase
  • The Cooling Phase
  • The Curing Phase

Let’s examine these phases to understand why Compost can harm your plants.

The Mesophilic Phase of Compost

At this phase, bacteria combine oxygen with carbon to form carbon dioxide and energy within the compost piles’ formation; that energy is used for growth by microorganisms. Any excess energy then leaves the pile as heat.

The compost pile temperature will rise to 111 degrees Fahrenheit during this first phase due to the proliferation of mesophilic bacteria. In this phase, mesophilic bacteria can include E. Coli and other bacteria that are harmful to humans; they are overcome by the heat when it nears 111 degrees Fahrenheit to around 125 degrees Fahrenheit.

The Thermophilic Phase of Compost

The rise in heat during the previous phase brings in the thermophilic stage. This is where the microorganisms become active, decompose the matter within your compost pile, and create even more heat.

During this phase, the temperatures within the pile can reach up to 158 degrees Fahrenheit. This phase only lasts a few days to a few months and will become localized in the area where new material has been added to the pile.

The compost pile will only have a few nutrients available at the end of the thermophilic phase. However, the microorganisms still have an enormous task since much organic matter will be left in a pile to digest and become useable Compost.

The Cooling Phase of Compost

After the thermophilic phase, materials will be left behind that were resistant to the rising heat; microorganisms left during this phase will return to the Compost and start digesting these heat-resistant materials. This is called the cooling phase. Macro-organisms such as earthworms and fungi are vital for forming rich Compost. These organisms will break up these coarser elements and move into the pile.

The soil would be very coarse and tightly packed if it weren’t for earthworms. They are a vital part of topsoil composition. In addition, there would be no way of supporting plant life within the soil if it wasn’t for earthworms; this is because the soil wouldn’t have any aeration, and the earthworms’ feces make an excellent fertilizer.

The Curing Phase of Compost

This phase of the composting process is a long yet vital one. Gardeners, unfortunately, can become very anxious and no longer want to wait for their Compost to mature fully.

The curing phase makes the soil healthy for consumption. This phase is a safety net that assures pathogens harmful to humans and has died off.

Composting at this phase can be deadly to some plants when a gardener is unwilling to wait. Substances toxic to plants, such as phytotoxins, are produced from uncured Compost. They contain elevated levels of organic acid and will rob the soil of nitrogen and oxygen.

Adding Compost is like adding Fertilizer, Almost.

Only when grown in a gardener’s backyard can Compost be considered a fertilizer. However, it’s legally not considered a fertilizer when manufactured by anyone else.

When grown in the backyard, Compost is a fertilizer because it’s organic, and through the phases we just discussed, the bacterium and fungi in a heap result in a slow release of nutrients.

Even though Compost can return nutrients to poor soil that plants need to stay healthy and grow, it is not the only answer to soil problems.

An amazing resource titled Composting for Beginners in the Garden also covers information, details, and tips on what makes and uses Compost.

Is There Such Thing As Adding Too Much Compost?

Soil being shoveled on a wheel barrow the a garden plot.

Some reputable, experienced gardeners will say this. They will say this because most gardeners and farmers always have difficulty producing enough Compost. So, having too much can be very hard to imagine.

As we have already discussed, it is quite obvious why smothering a lawn or Garden with Compost is not a very good idea, even if you decide to smother it with organic Compost. But, more Compost will smother the grass or plant, at least the part closest to the ground. If you damage that part, you’ll risk losing the whole thing.

Gardeners and landscapers frequently hear that transplanted trees and shrubs should be backfilled with amended soil (soil mixed with organic matter). However, organic matter is wasted if a mature tree’s roots will not reach where the hole has been dug deeper.

What happens to the soil if we add too much Compost

Also, if too much organic matter is used, the soil will decay as it subsides. Finally, water problems will result when the amendment creates a sharp delineation between unamended and amended soil.

Unlike most fertilizers, the nutrient content of other organic amendments and Compost is much lower. Therefore, there is a huge and slowly released nutrient load when Compost is mixed with soil at a 1:4 ratio or higher.

Nutrients already in the soil will have added nutrients and will even receive a boost in the activity of microbes when Compost is added. Therefore the nutrients added by Compost far exceed those in the soil already.

Experienced gardeners will often not know that good soil will contain only approximately 5% organic matter by weight, equivalent to about 10% by volume. Thus, overdoing a good thing in the Garden is possible, just like anywhere else.

So, you may think twice if you consider adding more Compost to your Garden. You may find that it has done more harm than you intended.

FAQs on Adding Too Much Compost

How often should you add Compost to your Garden?

It is best to add Compost yearly to your garden soil. Initially, adding a six-inch layer to be incorporated will provide good nutrition for microbial life. Then, add two to four inches in subsequent years to maintain the organic levels ensuring adequate feed for the microbes.

When should I add Compost to my soil?

Add Compost to your soil in the fall. This can be left on the surface for the worms to work through. Not only will it add nutrition and structure to your soil, but It will also protect the surface from compaction and prevent nutrient loss through winter storms.

Can I plant right after adding Compost?

You can immediately plant it into the soil after adding Compost, as Compost has already broken down and is no longer hot. However, animal manure, also called Compost, should be left until it smells like the forest floor (sweet) before planting.

Conclusion on Adding too much Compost to Your Soil

Like most things, too much of something can cause further problems. This can be said, too, when adding too much Compost to your soil. In this case, it brings more harm than good to the soil and plants, especially if it is manure compost.

Before putting in too much and risking all the harm to your beloved plants, it is highly suggested first to study what your Garden needs and know the soil’s ph level by doing soil tests.

We have a detailed article on the importance of soil testing, and you must know what your soil is lacking before amending it. You can view that article here so you know exactly what’s required.

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