Compost: Today’s Leftovers, Tomorrow’s Plant Food

The scraps on your dinner plate aren’t trash, they’re compost – the best plant food on the planet.

The key to successful organic gardening is learning how to make a great compost pile. When your garden plants are fed with compost, their need for supplemental organic fertilizers decreases, tolerance to diseases and pests increases, and your garden’s soil quality increases.

Healthy soil is the key to healthy plants

In the classic book, The Soil And Health, Sir Albert Howard, the father of organic gardening, wrote:  “the foundations of all good cultivation lies not so much in the plant as in the soil itself: there is so intimate a connection between the state of soil, i.e. its fertility, and the growth and health of the plant as to outweigh every other factor.” 

That passage, written in 1945, has only grown more true today. As research repeatedly highlights the damage that chemical fertilizers inflict on our gardens and the environment, the need to restore fertility to our soil each season with organic matter becomes ever more apparent.

Composting is an ancient practice

In the agricultural regions of China many years ago, villages would compost everything possible: the smallest twig, animal bones, spoiled food, even all of the human “night soil” waste. With these compost piles, Chinese farmers grew rice in the same fields for 2,000 years with virtually no plant diseases and plentiful harvests year after year.

In the Roman era, farmers knew that animal manures combined with grasses and other vegetable matter kept their fields sufficiently fertile to grow their crops. For centuries farmers used versions of this method until the advent of chemical fertilizers, or “artificial manures”, as Sir Albert referred to them.

Composted horse manure is magical

One of the best harvests from my garden was in the year I was able to get a pickup truck full of composted horse manure (mixed with straw), which I added to my usual compost pile of kitchen scraps and yard waste. The plants thrived and they produced a bumper crop. As a bonus I got to watch my wife, a born and raised city slicker until she met me, shoveling horse manure – that was priceless.

Compost breaks down into humus, which feeds the plants

Using composted manures and vegetable matter to restore fertility works because compost creates humus – the decayed organic matter from which a plant draws its nutrients. Composting your garden or field mimics the process that occurs on an undisturbed forest floor. When you lift back the top layer of leaves in a forest, that black, crumbly layer of earth, rich in decomposed organic matter, is called humus and that is what feeds the surrounding flora. Humus also helps the soil retain moisture and encourages good soil structure. 

Composting replenishes the humus which is used up by growing crops. Chemical fertilizers can provide the chemicals that help a plant grow, but they can’t restore soil fertility – only humus can do that – and humus is only derived from decomposed organic matter.

Compost can also be added whole to your garden, right from the kitchen, as in trench composting. It’s a great method to use over winter when compost piles may be frozen.

What can I put in my compost pile?

The rule of thumb is anything that was once alive, i.e. organic, can go into your compost pile. A short list from the Rodale Book Of Composting  includes:

• fallen leaves
• twigs and wood chips
• weeds (no seed heads)
• sawdust (natural wood only)
• grass clippings
• kitchen scraps
• garden and yard residue
• pet and human hair
• wood ashes
• shredded newspapers (black ink only)
• lint and sweepings

Compost mix: Browns and greens

The list of things that can be composted is very broad, but it’s the combination of “greens” to “browns” which is most important. This combination determines how fast your compost ingredients will “cook” or break down. According to the Rodale Book Of Composting, the ratio is 25:1, with “browns” being the higher number.

The “browns” are generally speaking, the crumbly, brownish, dry materials like fallen leaves, newspapers, straw, cornstalks, wood ashes, etc. The “greens’ are dense, wet substances like grass clippings, green leaves, green stems, blood meal, and poultry and wild animal manures. Green substances are high in nitrogen content and brown substances provide potassium and potash. It’s the greens that provide the food for bacteria to do their work on your compost.

Where most beginning composters fail is in the balance of greens to browns: Too many greens and the pile cooks too fast and gives off a putrid smell – too many browns and nothing seems to happen at all. With experience, one learns the right proportions for best results, and if you start with basic kitchen scraps, that will be close to the right green to brown ratio.

Air is crucial to composting

If your compost pile is giving off a putrid smell, it usually needs more oxygen. The actions of anaerobic bacteria, those that work in the absence of oxygen, usually deep within the pile, create a putrid odor. Your compost pile will eventually break down if undisturbed, but the humus will contain less nitrogen, as the anaerobic bacteria will have used much of it up.  The goal is to encourage more aerobic bacteria, those that work in the presence of oxygen. Their work leaves very little if any odor behind and you’ll quickly see your compost pile reducing in size, and changing shape and texture.

The key to encouraging aerobic bacteria is to make sure that your compost pile is aerated, either by stirring it or turning it on a regular basis – anywhere from once a week to once a month, depending on your weather conditions. This is the reason that the small home composting bins are made to tumble – to mix the ingredients and circulate air through the pile.

Water is important in composting

Moisture is important for proper composting. A dry pile means very little decomposition is taking place. Make sure that your pile stays damp like a just-used sponge, but not saturated. Too much water keeps the pile from heating up and may create a putrid smell, as it encourages anaerobic bacteria to develop.

If you’re having a dry season, make sure you water your compost when it needs it – when you squeeze the compost in your hand, it should feel moist, but not shed any water. If the season is rainy, cover your pile and only open it to the rain when needed.

Don’t fuss over the details if you’re just starting to compost. The important thing is to start today. Collect kitchen scraps and yard wastes and add them to this simple compost bin you can make at home. In time, you’ll learn what works in your pile and what doesn’t, how it cooks in different seasons, and what finished compost looks like.

But mostly, you’ll see the benefits to your garden plants. Higher quality fruits and vegetables, beautiful flowers, green foliage and fewer problems with pests and diseases.