Mulch is different to compost as it sits on the surface of the soil and works to hold moisture in and block the light to stop weeds from growing. Compost is made from broken down organic material which is mixed into soil to improve soil structure. Mulch can be made of bark chips, straw, sugar cane or hay.
Differences between mulch and compost
|Sits on the surface of soil||Mixed into the soil|
|Lay 2-3 inches on top of soil||Mix up to 1/3 through soil|
|Stops weeds||Improves sandy and clay soils|
|Breaks down slowly||Breaks down quicker than mulch|
Mulch and compost compared
Mulch and compost can be made of straw, hay, bark chips or mixed tree trimmings but in the case of mulch it is placed on the surface and for compost it is broken down over time to form humus. This mix would then be mixed into the soil.
The most important thing to remember is never to mix fresh mulch into the soil. The large pieces will absorb nitrogen from the soil as it broken down by bacteria which can starve your plants.
Using compost as a mulch
Compost that is used as mulch will also fertilize you water your plants or when it rains. This will wash nutrients from the compost down into the soil and give the plants an extra boost.
Compost can dry out quicker than mulch so add 1 inch layer of another type of mulch on top of compost like bark chips or straw to hold the water in.
Compost or mulch – Which is better?
Compost and mulch have different uses. Compost is better for mixing through the soil before planting, it will improve soil structure, add organic matter, help the soil to drain better and at the same time stop the soil from draining too well.
Compost improves sandy and clay soils by helping the soil to hold the right amount of water for your plants. Compost adds a range of nutrients to the soil including nitrogen and is a gentle fertilizer to help plant growth.
Mulch is better for placing on top of the soil around plants to stop weeds. A layer of mulch that is 2-3 inches thick will stop weed seeds from getting light and can stop almost all weeds from growing through.
Any small weeds that do grow through will be easy to pull out.
Is mulch a good fertilizer?
Mulch provides a gentle, slow release fertilizer when placed on top of soil. Mulch will be broken down slowly by bacteria and worms. When the bacteria break down the mulch, they will digest and then release nitrogen making it available for plants.
Mulch does not provide a rapid release of nutrients like a liquid fertilizer and mixing compost in will make more nutrients available to plants.
The best approach is to mix compost through the soil before planting and then top with mulch to stop water from evaporating from the surface of the soil.
How to turn mulch into compost
Mulch can be turned into compost by adding it to your compost bin or placing it in a large pile and letting it break down. A large pile of bark chips will eventually turn into mulch if left in a pile. This will break down from the bottom up, making a dark humus which can be dug into soil on the bottom layers.
The best and quickest way to turn mulch into compost is to add it to your compost bin, mixed with other ingredients. Old mulch works best, so if you have extra or if you are removing old mulch from a garden area, add it to your compost bin.
Mulch can be mixed with fall leaves, food scraps, coffee grounds and worm castings to make a rich compost mix.
Check out my previous article here on how to add mulch to your compost bin.
Mulch and compost disadvantages
The only disadvantages of compost and mulch is moving it around. If you live in a small apartment or townhouse, mulch and compost can be bought in small bags to move through to your garden.
If mulch is mixed into the soil the main disadvantage is that it can take nitrogen away from your plants. New and small plants are particularly sensitive to changes nitrogen and their leaves can quickly turn yellow if this happens.
Mixing mulch into soil will also cause water to drain away too quickly and your plants can dry out.
Use mulch the right way and put it on top of soil. Mix compost into your soil and your plant will be happy.
Mulching on top of compost
The best way to have a healthy garden is to mix compost through your soil and then mulch on top. The combination of compost and mulch is the perfect way to build a rich, organic garden with healthy, strong plants.
How to prepare soil with compost and mulch
The simple steps to preparing your soil with compost and mulch include clearing the soil ready to mix compost in and then topping with mulch. Check out these 2 easy steps below.
1. Clear your garden beds and mix in compost
Clear your garden beds of old mulch by raking it back from the surface. This will make sure that you don’t mix any old mulch into the soil. This old mulch can be placed in your compost bin to break down or topped up with new mulch.
Place home made or bought compost on top of the soil and use a garden fork to dig it through. Work the compost in to around 1 foot below the soil surface. Soil bacteria and worms will break down the compost over time mixing it into the soil.
2. Add mulch to the top after planting
Plant your new flowers, fruit trees or vegetables into the area that has been improved with compost. Backfill your plant with the soil and compost mix.
Add your mulch after planting keeping it 1-2 inches away form the stem of the plant to avoid rot.
Water your plant in well after mulching. This will help to hold the mulch in place and settle the soil and compost around the plant roots.
Water new plants regularly until they have established.
Is mulch the same as compost? – Summary
Mulch is different compost as it sits on top of soil, protecting soil bacteria, structure and your plants. Compost will improve compact, clay soils or sandy soils. It holds water and nutrients and will improve your garden soil over time.
I am an accredited practicing dietitian, experienced gardener and a dedicated cook. I love writing and sharing my experience so you can learn from my successes and mistakes.