Compost and mulch are gardening terms used interchangeably, and that is bound to create some confusion, especially for beginners.
For those interested in having a healthy and beautiful garden, knowing the difference between those terms is important because they serve different purposes.
Compost and mulch are not the same. Compost is mixed with soil to provide it with essential nutrients that enable plants to grow. Mulch is spread on top of the soil to limit weed growth, but it also helps retain moisture and prevent erosion.
In this article, we’ll speak about each one individually, and further explain the differences between them, and why they are used.
What is compost?
Compost is an umbrella term used to describe recycled organic material.
Compost is what you get when organic material is decomposed and turns into a nutrient-rich matter that can be used to enrich the soil and nourish the growth of plants.
You can obtain compost in a few ways:
- Buy it from your local gardening center or online via Amazon;
- Acquire it from a commercial composting facility;
- Make it indoors using a small composting bin or by creating a pile in your backyard.
The composting process is defined by how microorganisms residing in the soil break down the organic, carbon, and nitrogen-containing waste through aerobic biodegradation.
For that to happen effectively, an ideal environment must be created for microorganisms to thrive.
Science suggests the ideal environment should have these conditions met:
- Enough Soil – soil contains microorganisms that break down organic matter.
- Plenty of air – the compost mix must be turned daily or every other day to be aerated so that microorganisms have oxygen to thrive.
- Adequate water – the compost mix should be moist (not drenched) because microorganisms also require water to multiply.
- Carbon and nitrogen ratio of 30/1 – the compost mix should have more carbon-rich ingredients than nitrogen-rich ingredients.
- Small particles – big pieces of organic matter should be broken down into smaller pieces to decompose more rapidly.
- Optimal temperature – microorganisms give off carbon dioxide and heat, so the temperatures within the compost pile tend to rise, however, if too hot, the temperatures can kill off the all the microorganisms.
If these conditions are met properly, the decomposing process can take as little as two to three weeks – otherwise, it may take months.
Why is compost a good idea?
Compost helps reduce the amount of solid waste generated in a household and prevents it from ending in municipal landfills.
Unfortunately, when organic waste is put into normal garbage containers, it is taken to landfills where it rots and releases methane – a greenhouse gas that is 72 times more powerful than carbon dioxide.
Composting allows you to keep organic waste out of the landfills and convert it into a natural, eco-friendly fertilizer that can be used to grow plants.
Not only is compost good for the environment but it also spares your wallet.
What is mulch?
Mulch can be referred to as any material used to cover the surface of the soil.
It is used to retain moisture, suppress weeds, keep the soil cool, prevent frost heaving in winter, and make garden beds look more attractive.
There are two types of mulch: organic and inorganic mulch.
Organic mulch includes formerly living materials such as leaves, lawn clippings, shredded wood, straw, sawdust, pine needles, and similar items.
There are several benefits to using organic mulch:
- Minimizes soil erosion
- Moderates soil temperature
- Controls weed growth
- Encourages the growth of microorganisms
- Reduces the spread of pathogens
- Conserves soil moisture by reducing evaporation
However, organic mulch also needs to be replaced frequently because it decomposes and is prone to becoming displaced. Additionally, the materials in organic mulch may also create a habitat for pests if placed too close to tree trunks.
Inorganic mulch includes non-living life forms and man-made materials like rocks, plastic sheeting, rubber chips, and geotextiles (also referred to as landscape fabrics).
Even though they do not provide the same nutritional benefits to the soil as organic mulch, there are other benefits associated with its use, including:
- Moisture retention
- Low maintenance
- Doesn’t need to be replaced as often
- Effective in limited weed growth
- Have decorative appeal
There are also some cons to using inorganic mulch, starting with the fact it’s more costly and it may not be appropriate for all sites.
When is mulch generally applied?
Mulch is best applied from mid-to-late spring when annual weeds have not yet germinated and herbaceous plants are dormant.
It can also be applied in autumn as plants are dying back at this point.
New plants that need to be established can be mulched at any time as long as they can benefit from weed suppression and moisture retention.
But it’s important that you’re mindful about how much mulch you apply.
Excess mulch may cause your soil to be soggy, allowing plant diseases to settle in. If you don’t add enough mulch, it becomes difficult to prevent weeds from pushing through.
According to the Royal Horticultural Society (RHS), mulches need to be between 5cm (2-inches)and 7.5cm (3-inches) thick. That should suffice for most flower beds.
Difference between compost and mulch
Compost is typically mixed with the soil, while mulch is laid on top of the soil.
Compost is particularly effective at providing the soil with essential nutrients and improving the soil’s structure. Mulch is ideal for limiting weed growth, retaining moisture, and minimizing soil erosion.
In other words, they serve distinct purposes in gardening.
It’s important to note, though, that compost can also be used to cover the soil’s surface and act as inorganic mulch but with the bonus of providing the soil with nutrients. But from a technical standpoint – they are fundamentally different.
Compost is organic waste that has been decomposed and mulch can be either organic or inorganic material that is not decomposed.
For example, if you pick up lawn clippings and add them to a compost bin where they decompose and are transformed into fertilizer, those lawn clippings become compost.
If you grab lawn clipping and spread them across the soil around your plants, you are essentially using those lawn clippings as mulch.
Hopefully, with this example, it becomes easy to distinguish compost from mulch.
In this article, we have learned that compost and mulch are used for different purposes.
Compost provides the soil with essential nutrients and thereby promotes the growth of new plants. Basically, it’s a natural fertilizer.
Mulch is used to limit weed growth, conserve the soil’s moisture, and minimize erosion.
You can also look at compost as decomposed organic matter, while mulch is an organic or inorganic material that is undecomposed.
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