In November, I spread year-old compost in my community garden in the Intervale in Burlington. I love the feel of a handful of rich dark compost. I call it “Black Gold.”
One handful contains more microorganisms than people on Earth, from the tiniest microscopic decomposers to nutrient recycling nematodes to soil-moving earthworms. These creatures use carbon-rich organic matter as energy and, in the process of eating, release valuable nutrients like nitrogen into the soil. They also help trap carbon underground as they turn everyday waste products like food scraps and manure into fertile humus in your garden.
Compost is also useful for erosion control, land and stream reclamation, wetland construction, and as landfill cover.
Brown and green waste
What is “Black Gold?” Compost is decomposed organic material, such as leaves (brown), fresh grass clippings (green), old plants (brown), manure (brown and green) and fresh kitchen waste (green). It provides many essential nutrients for plant growth and therefore is often used as fertilizer and soil conditioner. Compost improves soil structure so that soil can easily hold the correct amount of moisture, nutrients and air. It improves the texture of both clay soils and sandy soils, making either type rich, moisture retentive, and loamy. It takes a period of months and up to a year for the materials to break down into humus. It depends on the ingredients in the pile and how many times you turn it. I attempt to turn my piles at least once. More on heating, moisture, aeration and smell below.
I’ve been making compost a long time. I starting working at Hill and Dale Farm in Putney in the spring of 1969. We made compost in 100-foot long windrows from cow manure mixed with bedding material. Compost made from animal manures is higher in nutrients and quality than those from vegetable scraps, hay and other organic materials. By the way, the nitrogen produced in the piles comes from cow urine. I use my urine mixed with water and pour it on my compost piles like I just did on the solstice.
The carbon to nitrogen ratio
The course of decomposition of organic matter in a compost pile is affected by the presence of carbon and nitrogen. The C:N ratio represents the relative proportion of the two elements. A material, for example, having 25 times as much carbon as nitrogen is said to have a C:N ratio of 25 to 1, which is an ideal ratio in a backyard compost pile. The ratio composting animal manure and bedding material is 12 to 1. If there is too much carbon, decomposition slows when the nitrogen is used up and some organisms die. I have found over the years that in many backyard compost piles there is too much carbon and the pile doesn’t heat up.
Heat, moisture, aeration and smell
The four Greek elements: Fire, water, air and earth.
The first stage in the breakdown in the compost pile is fire. The optimum temperature range is 135-160 degrees Fahrenheit during the heating stage. You’ll burn your hand if it’s too hot in the pile.
The next stage is water. The amount of moisture is also critical in a pile. It should be damp but not wet. Use your hand to check this out. Make sure to aerate the pile by turning it.
When the compost is complete, it should smell sweet. Use your nose. I once knew a gardener who tasted well-composted manure. Hmm!
To summarize, composting takes place as a multi-step, closely monitored process with measured inputs of water, air and carbon- and nitrogen-rich materials. The decomposition process is aided by shredding the plant matter, adding water and ensuring proper aeration by regularly turning the mixture when open piles or “windrows” are used. Fungi, earthworms and other detritivores further break up the material. Aerobic bacteria and fungi manage the chemical process by converting the inputs into heat, carbon dioxide, and ammonium.
Understanding how to make and use compost is in the public interest, especially today as the problem of waste disposal grows. So start now! Save the environment and build your own compost pile. And remember that without compost, soil would be dirt, the stuff you drag into your house when you forget to take off your shoes. Soil, on the other hand, is our life support system. It anchors plant roots, creates habitat for millions of critters, filters water and holds nutrients.
I’ll write about soil regeneration in my next article.