Compost and Mulch - Do We Know the Difference?

Differences

Do we know the difference between compost and mulch?

I admit that I get a bit confused which is which as definitions can be very vague. I tend to use them both in the same way, just putting them on top of the soil and letting the worms do the work.

There is a difference though and I was chatting to Rosie Harding this week who is a bit of an expert in the field.  Rosie and her husband Peter have regenerated a piece of degraded land in Goa, India, into an abundant and productive kitchen garden and food forest. I asked her how they differentiate between mulch and compost and why it’s an important part of their garden.

What is Compost?

“Compost is decomposed organic material”, Rosie tells me. “It is person made, commonly using a mix of kitchen scraps and wet and dry garden leaves, grasses and trimmings. When it is ready it is a deep dark brown, almost black, feels moist and crumbly to touch, and does not smell bad, but has an appealing earthy smell.

At its simplest, compost is a pile of organic matter that will decompose by itself in as little as 18 days but can take many months, depending on the content and season. At its most organised, it is a recipe blend of wet and dry materials, a specific ratio of nitrogen and carbon.

When organic matter decomposes naturally on the forest floor in nature, it is called humus.

Benefits of compost:

• Increases the soil’s ability to both hold moisture and drain better all at the same time.
• Nourishes your plants.
• Adds important microorganisms and fungi to the soil (which are part of an important and often overlooked soil foodweb that is actually what is feeding your plants)
• Improves soil texture.
• Has insulating qualities against heat and cold.
• Helps to break down the mineral elements of your soil (ie pebbles) and contributes to making those nutrients available to the plants.
• Compost can be used to make suitable potting mix to germinate seeds.
• It can be easily side-dressed into the soil next to a plant that may require a “nutrition boost”.

What is Mulch?

“It is any type of material that is spread or laid over the surface of the soil as a protective covering. It can be in the form of living mulch, growing in and over the ground, or a layer of mulch material on top of the soil, for example dry leaves or straw.

Benefits:

• A thick layer (think at least 2 to 3 inches) of dry leaves or straw will immediately cut your watering requirements by 50%, from Day one.
• Protects the soil underneath from the harsh sun and lashing rain.
• Suppresses weeds.
• Reduces erosion.
• Provides habitat to frogs, lizards and other garden friends.
• As it breaks down, it provides food to the microorganisms & fungi already present in the soil.
• In the case of living mulches, which can also be in the form of “green manures”, the roots are also benefiting the soil, helping with aeration, and with both drainage and moisture retention equally.

Why the confusion? “You may find references of compost being used as mulch, especially in Ireland as it is a temperate climate. Here in the tropics a protective layer of mulch is really important for retaining soil and protecting it from the elements such as scorching heat and torrential rain.

A common mistake is to dig mulch into the soil, instead of placing it on top of the soil. This will cause a temporary nitrogen deficiency as the nitrogen in the soil is used up breaking down the carbon of the un-decomposed or only partially decomposed mulch.

A tip for those with smaller spaces in urban and suburban areas, including those with potted and terrace gardens. When people in these areas ask what the best thing that they can do for their soil is, the answer is always Mulch, Mulch, Mulch.

Given the huge quantity of leaves that are burnt or otherwise disposed of every year as part of “tidying” homes and gardens, it’s possible to rapidly collect large quantities of mulch. As much as you may need for a few pots, and way more for those that can use even larger quantities. And you can never have too much mulch. Mulch is absorbed extremely quickly into soils that are poor in organic material, and over time, as the organic material builds up, the rate slows. If ever you really do get your hands on “too much mulch”, then you can compost it.” Rosie concludes. see their page here

As we are on the subject of differences, did you know these too?

Briefly

Differences: Hay and Straw

Hay is a crop that is grown specifically for the purpose of creating hay, while straw is a byproduct of different kinds of crops. Hay is geared toward being a nutrient-rich food for livestock, while straw is more often used for bedding instead of food. Straw also has a wide variety of uses, for everything from a compost pile to an energy source

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Differences: Cacti and Succulents

What define true cacti are areoles. Areoles are what spines, spines, branches and flowers may sprout from, and all cacti have them, while succulents don’t. Areoles are not hard to find – they usually look like small, fluffy, cotton like lumps on the body of the cactus.

So, the next time you look at a succulent, look to see if they have areoles. Then you will know for certain that it is a cactus, or not. 

Remember though, there are exceptions to every rule.