Using Compost as Mulch: The Benefits and Usage Tips


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Compost and mulch play key roles in the garden. Although they may seem different from each other, compost can be used as mulch in most cases.

Using compost as mulch is a cost-effective method of covering topsoil, which adds nutrients to the soil, prevents weeds, retains soil moisture, boosts microbial activity within the soil. Compost should be applied in a layer of 2 to 3 inches on top of the soil in an area where there is minimal sunlight and wind.

Compost can do wonders while being used as mulch and helps in making soil happy. It acts as good organic fertilizer and effectively reduces soil erosion. 

This article gives much detail on the benefits of using compost as mulch, the benefits, and what you can do to ensure it is used effectively as a mulch.

Can Compost Be Used as Mulch?

Compost as mulch

When compost is added on top of the soil, it provides the plant with additional nutrients as well as the benefits that come with mixing compost with soil.

Compost can be spread uniformly onto the soil as a cover which would provide a number of benefits for the soil beneath similar to regular mulch. It can be added to both potted plants and garden soil.

Some of these benefits are:

  • Protects against temperature changes
  • Retains Water.
  • Mulch Adds Nutrients
  • Mulch Helps Prevent Erosion
  • Mulch Encourages Earthworms and Microbial organisms
  • Prevents Weeds

Yes, compost is considered the best mulch for organic gardeners. By using compost as mulch for perennial beds you can achieve great results. Compost mulch makes plants grow faster and it decreases the damage from pests and diseases.

In studies from all over the world, scientists have found that installing a compost mulch decreases pest damage and produces bigger flowers and vegetables. It enriches the soil without altering the existing soil flora or fauna.

Compost used as mulch showed promising results as compared to bark and wood chip mulch. Organic waste can significantly increase plant growth. The nutrients are available to the soil adequately. Production of stems and leaves can increase by their use.

Quality matters a lot while using compost mulches because it will act as the primary medium for plant growth, it should be decent in quality. 

Moreover, you can apply compost directly on top of soil before planting. It helps renourish soil long before plants are added.

What are the Benefits of Using Compost as Mulch?

Compost-type-mulch has enormous benefits. It can help in plant growth ranging from maintaining the pH to fighting for plant diseases. Orchard ecosystem gets benefits in managing weed, fungal, and pests control by using compost mulch.

Composted soil needs no additional fertilizer for growth. Compost mulches are a better substitute for chemical fertilizers. Mulching is adding a top layer to protect plants. In contrast, compost mulch provides protection and nutrition with both.

The benefits of using compost as mulch; a few are elaborated below;

Boost plant growth 

Compost has many benefits, including nutrients, water retention properties, microorganisms, and soil builder insects. It helps in balancing PH, neutralizes various toxins, and acts as natural organic fertilizer. All these necessary factors give a boost to plant growth.

Additionally, roots will tend to grow, spreading out through the soil to access the increased nutrients from the compost.

Boosts Microbial activity Within the Soil

Mulching causes a significant increase in bacterial and fungal richness and diversity and played important role in shaping microbial community composition.

Microorganisms play a major role in the composting process. They use the organic matter in the compost bin or heap as a source of food resulting in its decomposition to the rich brown material we know as compost.

The “On-Farm Composting Handbook” gives examples of the numbers of each group of microorganisms present.

  • Bacteria 1,000,000 – 1 billion present per gram of compost.
  • Actinomycetes 100,000 -100 million in a gram of compost.
  • Fungi 10,000 -1,000,000, fungal cells per gram of compost.
    [Source]

With this data, we can see that simply mulching with compost can improve soil health by introducing millions of living organisms to the soil.

Increase soil nutrients: 

Potassium, nitrogen, and phosphorus are the critical nutrients for plant growth. Compost contains organic material and has these three primary nutrients in plenty. Sometimes gardeners overlook micronutrients. 

Composted mulch has boron, cobalt, zinc, iron, iodine as micronutrients. Hence, provide optimum plant growth. The number and amount of nutrients depend upon components mixed in compost formation.

In addition, the major increase in microbiological activity as mentioned above can cause more of these nutrients to be available for the plant as these organisms further break down organic material within the soil.

As a result over time, the soil level may begin to drop when the organic material is consumed. 

See the detailed post on how soil level drops over time.

Slow-release of nutrients to the soil 

Are you concerned about the release or availability of nutrients? No need to worry; your problem can be solved by composted mulch. In spring, plants start to grow slowly. On the other hand, microorganisms release nutrients slowly. 

When the weather gets hot, nutrient production increases by microorganisms and plants grow faster too. It’s a beautiful natural process, but you can get slow-release nutrients from this type of mulch.

Retains moisture

Compost can increase the water holding capacity of the soil. It can contain 200 times more water than its dry weight. Small crumbs and aggregates form after organic matter binds with the earth. 

Simple soil has more tendency to act like cement on wetting. While crumbled soil makes aggregates, it can hold water and make it available for plant growth. It also helps in water drainage through crumble channels.

This allows the soil to hold moisture much longer after watering which increases the watering intervals and saves on water used on the plant.

Can be applied all year round

The perfect compost can take between three and twelve months to create. Decomposition depends upon the organic materials used in the formation of compost. 

Once you have attained the finished non-lumpy form, you can use it anytime. You can add it to soil all year round without fear. At this stage, it will not sting water or burn plants.

Prevents Weeds

A thick layer of mulch compost helps prevent the seeds from ever reaching the soil. As for the seeds or roots that are already in the soil, mulch blocks one of a plant’s essential needs, sunlight. Weeds will try to fight their way through, but if your layer of mulch is thick enough, it will suppress all but the most resilient.

How to Mulch with Compost?

You can mulch with compost in two simple ways. Make a proper neat soil surface and apply compost in a thin layer on top of the soil. Compost is available in aggregated form. So, it will help worms and other beneficial insects to penetrate in soil.

These tiny creations will help compost in melting down and adding in soil. Thus, it provides nutrition to plants and mimics weed growth. 

Water retention is an additional benefit. Suppose you do not have any garden, no problem. You can spread a compost layer in indoor plant pots.

Another way is somewhat similar to the one mentioned above. Compost is applied as a thin layer, but it should not be dry. Any dry mulch will not allow roots to grow properly. 

In case of dry compost, add a layer of another mulch over it. For example, chopped leaves will help in retaining water. And keep plants biologically active, e.g., fruits, vegetables, etc. 

Can too Much Compost hurt plants?

Adding “black gold” means compost to your soil gives a high dose of nutrients. Sometimes too much good can be proved as an overdose, which produces a fetal effect and kills plants. 

High levels of soluble salts can shunt plant growth. Excessive nitrogen, sulfates, and phosphorus from organic fertilizer burn the plant. Iron is added to soil as a phosphorus antidote.

An elevated amount of phosphorus increases mycorrhizal fungi growth in plants. Make sure it will not harm your field. An appearance test will be helpful, as it should be in crumbled form.

If you are making compost from the municipality, always ask for quality. Rotten hays come with broad-leaf herbicide. It causes harm to the plant leaves. You have to clean your ground from all types of grasses.

If not, grasses still tend to grow through the compost mulch. Compost is an excellent place for bacteria. Worn-out compost may infest your garden soil with disease-causing organisms. Disease-causing organisms can kill plants.

The Downsides of Using Compost as Mulch

Sunlight can Harm Microorganisms

Microorganisms are accustomed to dark moist conditions within a compost bin or pile. 

When the compost is spread over the soil, the exposure to sunlight can cause heating of the compost, potentially killing the ones closer to the surface which is directly exposed.

As a result, this drives them down into the plant soil to seek refuge which will be beneficial to the plant and soil.

The Sun and Wind can Dry out the Compost

Being exposed to the elements, compost when used as mulch, will be exposed to wind and sunlight. 

Wind and sunlight, especially when coupled together, can quickly dry out the compost causing it to become grainy and extra light. As a result, high winds will cause the compost to be easily blown away.

Compost mulch can also be lost when the soil is watered or when it rains heavily as the lightness of the compost will cause it to float and wash away.

See our detailed post on how to prevent mulch from washing away.

When using compost as mulch you should consider placing the potted plants in an area where it is not exposed to sun and wind.

As for garden plants, providing shading can help reduce both wind and sun from directly hitting the surface of the soil and mulch.

Can you Use Manure as Mulch?

Manure is produced from mostly livestock waste through natural decomposition by microorganisms. Compost is also a product of decomposition, but it is controlled. The end result is two similar products which only differ by the way they are produced.

As a result, manure can be used as mulch and bring the same benefits as compost and other types of mulches.

Manure will have much more nutrients than compost and the results will show in a shorter period of time.

If you need to replenish your old mulch, here’s a good option that I have tried and tested and it comes at a great price.
You can find it here!

Cedar Mulch

Using Sand as Mulch

Sand, when used as a mulch, increases the aesthetics of the garden by contrasting the greenery of the plant with a white background.

It also prevents weed growth and protects the topsoil from water loss and pests like gnats and fungus. Additionally, it can be used as an amendment that helps increase soil drainage and aeration.

Sand has a grainy texture with numerous air spaces. This characteristic makes it good enough to allow water to pass through easily. 

Sand is a great material to use for mulching and is recommended due to its benefits. 

There are so many advantages of using sand as mulch which includes:

  • they make excellent bases,
  • they have very wonderful accents,
  • they are a great choice as compared to grass,
  • they are cheap and they last longer.

The Takeaway

Using compost as mulch saves money, is easy to gather and apply, contains many nutrients for plants, and doesn’t require tilling or mixing into the soil. Moreover, compost is an excellent method for controlling weeds in garden beds, flower beds, or anywhere mulching is needed.

Composts are heavy and take time to move. Establishing proper beds as mulch will provide lots of benefits. A paper and pulp sludge and ash compost can be used as a soil amendment mulch. It helps in lowering the burden on landfills. 

But compost can be harmful if any mishandling occurs. A small example includes overheating. Compost is usually black. It allows heat penetration and is hot in summers. Compost placing as mulch requires caution to obtain benefits.

JayLea

JayLea has a passion for plants and has been gardening since 2015. He has valuable knowledge about gardening and houseplant care and can answer everyday practical questions that every plant owner has.

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