How Does Composting Work?

3 tips for starting your compost pile

Backyard composting can be one of the most rewarding aspects of gardening. But how does composting work? The answer to that is simpler than you might think.

Compost is basically the decomposition of organic matter. After the organic material decomposes, it becomes a dark, crumbly material called compost. This compost can then be mixed into your lawn or vegetable or flower gardens to improve soil makeup and aeration. Read on to learn how composting works, how it benefits your garden and how worms can be used, and discover some top composting tips.

Garden composting

Composting is great for your garden because it improves the soil, and it’s great for the environment because it reduces your household waste. Instead of throwing your kitchen waste in the garbage, you can throw it in your compost pile and use it in your garden. You can put your compost pile either in an open bin or a closed container, like a large trash can or bucket with lid.

According to the The Garden of Oz website, the most important thing is that you have the right combination of green and brown materials in your compost pile. Green materials include grass and yard clippings and kitchen scraps like fruit, vegetables or coffee grounds. Brown materials include dead leaves, dried grass or hay, straw, sawdust, shredded newspaper or shredded cardboard. The proper mixture of brown and green keeps the pile aerated yet moist; you don’t want it to be too dry or too wet.

Another important composting tip is to turn your garden compost pile often to keep it well mixed. Chopping or shredding whatever you throw in will speed up the decomposition. When your compost is fully decomposed, it will be a nice crumbly composition that you can easily mix into or spread onto your garden. You won’t be able to tell what any of the original yard or food scraps were.

Worm composting

Worm composting is also called vermicomposting, and is different from starting a compost pile.

According to Mary Appelhof, author of the book Worms Eat My Garbage, worm composting can be done by putting certain types of worms in a container in order for them to digest kitchen scraps. The worms then eat the scraps and cast off their waste, which creates a rich compost or fertilizer. If you don’t want to go all the way with vermicomposting, you can toss a few worms into your compost pile and they will still produce a beneficial result. Appelhof says that worm composting is often a solution for people who don’t have the room for a traditional compost pile or bin.

Top composting tips

According to Sunset magazine, composting comes down to decomposition. And for optimal decomposition, the top composting tips are:

  • Make sure your pile is a good mix of green and brown materials
  • Turn, turn, turn
  • Keep it moist and aerated

How does composting affect soil?

According to Dr. Francis Rayns of the Elm Farm Research Centre and the Initiative on Organic Research, composting produces vital nutrients such as nitrogen, potassium and phosphorous. Rayns adds that these nutrients make your soil healthier by creating a greater diversity of soil organisms and improving soil structure and water retention.

Composting adds vital nutrients

Healthy soil is essential for successful fruit, vegetable and flower production. According to Rayns, adding compost to your soil supplies plants with nutrients while suppressing plant pathogens. These nutrients improve soil structure by boosting its water-retaining qualities, drainage and root development and penetration. Rayns also says that adding compost to your soil adds to the organic matter in the soil.

Compost affects the soil pH

According to Florida’s Online Composting Center, compost can affect soil pH, depending on its ingredients. For example, compost that contains acidic materials, such as pine needles or oak leaves, can have an acidifying effect on soil. According to University of Massachusetts researchers Frank Mangan, Allen Barker, Steven Bodine and Peter Borten, compost can help balance the pH (or acidity or alkalinity) of soil, and the pH of finished compost is usually slightly alkaline.

Different ingredients equal different nutrient levels

According to Mangan and the other researchers from the UMass Vegetable Program, nitrogen levels in compost will fluctuate according to the source material and how it is composted. Also keep in mind that not all nutrients are immediately available for plant use.

Know when it’s ready

According to the UMass Vegetable Program researchers, your compost is considered mature (finished or ready) when the nutrient and energy levels have combined to become a stable, organic mass. Only when this has happened will your compost contribute to healthier soil. The composting process creates a dark-brown, crumbly material.

You shouldn’t be able to recognize the original components in this material, meaning you shouldn’t be able to see any eggshells, banana peels or anything else you added to your compost pile or composting bin; these materials should have all fully decomposed. This full decomposition can take anywhere from a few weeks to more than a year.

Ensuring your compost is finished before adding it to your soil is very important, because adding unfinished compost could adversely affect plant growth. The UMass researchers recommend waiting a week between applying your compost to your soil and planting any vegetables, trees or other plants.

Know your compost composition and soil analysis

The UMass researchers also recommend a soil test or soil analysis to evaluate the effect of compost on the fruitfulness and health of your soil. The soil analysis should be performed after you’ve applied your compost. Soil tests measure available plant nutrients, soil pH and heavy-metal accumulation in the soil.

According to the University of Missouri, it’s preferable to know the nutrient content of the compost material that you plan to apply to your garden or lawn, because you can adjust compost amounts based on that soil analysis. You can get these analyses done at soil testing facilities, and they are relatively inexpensive. A complete compost and soil analysis package will test the levels of nitrogen, potassium, phosphorous, magnesium, iron, carbon, zinc and other nutrients. The compost and soil analysis will also test the carbon-nitrogen ratio, pH and electrical conductivity.

If you don’t want a complete analysis, you can pay to have your soil or compost tested only for certain nutrients. It will take between two and five days to receive the results of your soil or compost analysis. Soil sample analysis from the University of Missouri, for example, can take up to two working days, and plant or compost analysis can take four to five days. Requested sample sizes also vary among testing facilities. Holmes Laboratory, for example, asks for a gallon of compost to be tested.

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