What is composting?

Composting is a method for making food scraps and other organic compostable waste into nutrients for plants. You pile up leaves, twigs, melon rinds, egg shells, coffee grounds, etc., and wait for them to rot. You occasionally turn the pile so it stays aerated. Microfauna in the compost breakdown the various bits until they become a rich, black-brown humous that can be used as soil amendment in the garden.

When compost is added to the garden, it achieves the following:

  • Adds nutrients and humous to the soil, enriching your topsoil.
  • Increases the soil’s tilth (suitability for sprouting seeds.)
  • Allows the soil to soak up rainfall faster.
  • Allows the soil retain that moisture in the soil longer.
  • Moisture retention means less runoff.
  • Less runoff means better erosion control.
  • Better erosion control means
    • water tables are more likely to get replenished and
    • plants are more likely to establish properly, thus
    • allowing increased evapotranspiration, thus a more predictable rainfall climate.

So many goals are accomplished in a chain of events that is self-sustaining when we properly manage our soils!

What is Mulch?

Garden-prepped mulch includes materials like:

  • Pine straw (Preferably new, not composted)
  • Pine bark (New, not composted)
  • Hardwood Bark (6-months rested)
  • Wood chips (6-months rested)

Composting is well supplemented by the practice of mulching, a layer of unrotted or partially rotted organic matter applied on top of garden soil. It’s usually ground-up bark, twigs and leaves combined together and partially composted so that they can be spread as a layer that slowly decomposes over your garden.

Pine straw and pine bark can be applied directly to the surface of a landscape because they breakdown very slowly under the normal conditions. Wood chips (both hard and soft) generally require a resting period of about six months before they can be safely applied as a garden mulch because they rob the soil of nutrients during the first part of their composting process. Mulch always breaks down after a season or two, adding to the humous layer of the soil, basically finishing off their composting while covering your garden. In many ways, mulch is actually more effective in achieving long-term tilth, water-retention and run-off goals than compost as a soil amendment for the following reasons:

  • Because compost is usually incorporated into a soil, this ends up disturbing soil strata during rototilling (incorporating as a soil amendment). On the other hand, mulch is always applied on top of existing soil strata, so worm layers and fungal layers that are important to root growth and development remain unharmed as new nutrients are gently applied from above on an annual basis. The less you mangle the soil strata, the better your long-term plants like shrubs, trees and vines will be able to establish and endure climate extremes like drought and flood.
  • Mulch is a human-enhanced method of ensuring the soil strata remain intact while slowly providing nutrients in a landscape.
  • Mulch not only has the benefits of soil moisture retention and erosion control, but also often aids as weed control as well in more more formally-maintained garden areas.
  • Mulch generally locks a lot of carbon in a useful layer on the top of the soil, making it less available as an agent of global warming.

If you’ve ever kept a mulched space, you know how easy it is to plunge a planting trowel down into the soil below the mulch when you’re planting annual flowers, especially at the beginning of fall planting season. You’ve probably seen the richness of the soil and lots of worms as you dig easily into the soft strata that mulch creates.

When should I use compost vs mulch?

  • Compost is usually added to newly created garden beds where topsoil is thin or not well established. It’s also used in seasonally planted beds for things like vegetables and annual flowers. Compost is incorporated into soil as an amendment, usually by mixing it into the soil so the existing soil behaves more like normal. You’re basically adding natural nutrients to the soil.
    • Note that some compost processes include vegetarian herd-animal poop. Unlike poop from meat-eating animals, herd-animal poop has been generally recognized as safe for compost use for centuries. When herd-animal poop is included in the process, the compost has to be brought to a temperature high enough to “cook” the seeds the animals eat. That way the compost won’t become a source for unwanted weeds. Compost that incorporates herd-animal poop is often more nutrient-dense than compost without. It should smell like clean sweet earth – not poop – if it’s composted correctly.
  • Mulch is often used in human-made landscapes and vegetable and flower beds as a top dressing for weed control, erosion control and moisture retention. It’s widest use is as a topdressing in places where no understory growth is planted under trees, around shrubs and between newly established plant groundcovers. Mulch ideally contains mostly brown material (bark, leaves, twigs) that is not fully composted, and mostly weed-seed free.
    • Under most circumstances, we want wood chips to be partially composted before the mulch is spread over a landscape. However, wood chips that are fresh — uncomposted — may be used for walking paths. They become useful because fresh wood chips rob the soil of nutrients, stunting weed growth along the path.
  • Thinking critically, we have to remember — if all we have is either fully composted material or mulch and the land needs preservation, top dress with whatever you’ve got! The rest will take care of itself with time and patience.

Who uses Compost and Mulch?

That’s the crux of this site! We’ll be exploring these parameters in depth on other pages and posts on this site, and link to those with fuller explanations.

More of us should be using compost and mulch in our landscapes and gardens. And it’s not just about improving the local soil strata, local water table, and local environment in general. It’s also about getting local governments and businesses to also use compost and mulch in their landscapes and gardens that are provided from local sources. This keeps the nutrient chain local, reduces the need for artificial fertilizers and gets compostable organics out of landfills. Landfills that are allowed to bury organics slowly release methane, a gas that is twenty times more harmful than carbon-dioxide at increasing global warming.

This is why we need everyone to think seriously about collecting and maintaining a compost bin. Get your greens and browns to your own compost bin outside, or for those in more urban settings, get local legislature to enact laws that require landfills to keep organics out of the landfill, create a county or city compost site, possibly partner with local compost businesses, and use the compost and mulch locally for so many reasons.

What’s this about Brown and Green materials?

Compost and Mulch require different ratios of “brown” materials to “green.” Mulch is pretty much just brown. Compost will rot faster or slower depending on the amount of green materials added to the brown.

  • Interactive Composting Tool – “Can I Compost…” at the website “honestly modern”.
  • Recipes for Compost
    • Vermicomposting
  • Recipes for Mulch

Additional Materials, Links

Thanks to Brenda Platt of ILSR for these!

Mulching/composting is great for cropland soil retention. Here’s a government study that describes what’s happening with cropland, why and how we need to protect it.

A climate alert message from FAO about why we need to get compostable organics out of landfills and engage in composting now.