GARDENING: Compost — from waste to garden wonder

Nature has been composting ever since life began. The death of organisms triggers self-digesting cellular mechanisms. Other organisms then recycle the resulting debris. Natural composting – such as leaves on the ground or plants and animals decaying where they have fallen – has occurred for billions of years, creating the rich soils of today.
Garden composting involves accumulating various biological materials in a dedicated area. It can be as simple as mulching the lawn grass with a specific mower blade that deposits the fine cuttings on the lawn soil surface allowing fertility to build up. Or, why throw lawn grass cuttings over walls of neighbouring fields when you use them to fertilise your own garden? Grass clipping that are collected are a great addition mixed into compost piles. They are high in nitrogen and add aeration to the pile if mixed well.
So called ‘chop and drop’ composting involves cutting plants down leaving them where they fall in contact with the soil to decay, releasing their mineral and carbohydrate goodness. Collecting leaves from unwanted locations is a wonderful source of material for compost, but leaves should be left where they fall in ecologically rich areas, as they are an important overwintering habitat for many creatures. Compost piles themselves are great habitats for insects which are sadly in rapid decline.

Aim for moist
Everything that made from something that was once alive can be composted – all foods, paper, basic cardboard, leaves and wood. And if you’re hardcore, even shells, hair, nails, teeth and bones! These latter materials will decompose naturally but very slowly, depending on acidity of the soil. Dissolving in acids accelerates the decomposition of mineral-dense materials. Shells and bones can be crushed to increase the exposed surface area. The resultant mineral liquid can then be added to the compost pile or diluted down and added directly to the soil.
Hydration is important with all biological systems, including compost piles. Too wet and air cannot penetrate and too dry and the biology dies off. Just moist is perfect for peak decomposition activity. Covering your pile with a plastic tarp or cardboard is a great way to trap moisture and heat inside and keep the biochemistry at peak performance.

Timing is everything
For a fast-processing compost pile combine carbon-rich ‘brown’ materials, such as brown leaves, paper, cardboard, hay, wood shavings, with nitrogen rich ‘green’ materials, such as fresh plants, coffee grounds, tea leaves, manures, green grass cuttings.
Scientific trials suggest the perfect carbon to nitrogen ratio is about 30:1, but in reality, for the amateur gardeners, keeping it simple with about half carbon material and half nitrogen material is recommended.
Hot composting occurs when the microbiology have near perfect conditions regarding food, moisture and oxygen. The nitrogen and carbon biochemically react with oxygen to release quite an amount of heat. It heats up rapidly often above 70ºC and is usually complete within weeks.
Cold composting is where conditions are less favourable but require less care taking and can take one to two years to mature. In reality, most garden compost piles tend to be somewhere in between.
A very fast but labour intensive method of composting involves mixing about 50:50 brown and greens, naturally getting the temperature of the pile to 60ºC for four days, and then turning the pile every two days for 14 days. Eighteen days later, the compost is mostly broken down.

Safety considerations
Full decomposition of compost can take years, so compost can be seen as a slow-release fertiliser. Fresh foods and meats do attract rodents so a finer metal mesh can be used. A provisional sealed food waste bin can also be used to partially decay and make food unattractive to rodents.
Vermicomposting using worms is another great way to create amazing compost teeming with soil biology – the worms consume the softened food, fungus and bacteria; microscopic nematodes consume bacteria; and bacteriophage viruses explode open bacteria, including harmful E-coli, making compost safe.
If the compost pile does not get enough air, and specifically oxygen, it becomes anaerobic and a different set of organisms take over, producing offensive gases – but it still composts. Once oxygen becomes present these organisms die off and aerobic organisms take over the decomposition process.
Despite rumours to the contrary, diseased plants can be added without problem. Well-rotted compost will eventually break down bacteria, viruses and parasites, so it is very difficult to spread disease using mature processed compost.

All in the mix
Matured compost is usually about neutral pH, so it is ideal for almost all growing situations. One thing to bear in mind though, it is not recommended to grow plants in pure compost – the mineral content can be too concentrated. The plant roots prefer a mosaic of compost topsoil with subsoil containing small stones, sand and other inorganic compounds that aid drainage, aeration and act as slow-release mineral sources.
I’ll leave you with one last thought. If you are ready for next level composting then it is ‘humanure’, which converts human waste – a resource-draining pollutant – into a nutrient-rich asset. It seems to me not many are ready for that discussion, however….

• Oliver Whyte’s garden, Coill an Chúir at Sandyhill, Westport, is included on the Clew Bay Garden Trail. A chain of beautiful and unique private gardens, the trail opens to the public during summer to raise funds for charity (see www.clewbaygardentrail.ie for more). Each month, an article by a trail member appears in these pages.