Last weekend we had a compost 101 class at Concho. We went through the processes that make a compost pile successful and the things that gardeners need to know to make sure the process goes well. I know that not everyone was able to make it out to the class so here are answers to some important questions about composting:
What is compost?
Compost is not the same thing as soil. Compost is considered a soil additive, because it improves the quality of almost every type of soil. Compost helps sandy soil retain water, and it helps clay-heavy soil drain better. The active colonies of micro-organisms in compost help plants to fight diseases. Healthy plants start with healthy soil.
How does composting work?
Many different types of micro-organisms work together to digest plant matter into the finished product that we use. Both bacteria and fungi are at work in a compost pile. When enough digestion is taking place in the pile, it starts to heat up. On a cold day, you can even see steam! We want to give these organisms the ingredients they need to work fast and heat up. Heat kills seeds and diseases. After the process has stabilized, which can take a few weeks to a few months depending on the amount of care a pile is given, we are left with an earthy smelling soil additive.
How can I make this process successful?
The organisms that make good compost require four basic things for success. The first two are carbon and nitrogen. These two elements are present in all organic matter. What is important is the ratio between these two elements in the pile. The optimal ratio is C:N 25-30:1. We control this by adding different amounts of materials with different ratios. Things that are green and wet, like vegetables or coffee grounds, usually have C:N ratios of 25:1 or less. We balance these “high nitrogen” materials by adding things that are brown and more carbon rich like dried leaves, which are around 70:1 depending on the species. This link has a table with some common items. The C:N ratio is approximate, and it will never be exact. We just try to make sure that the piles don't get too full of dry leaves and carbon heavy materials because then they cool down and work slower.
Water is an essential item for life so it is essential for the compost organisms. A pile should be damp throughout. If a lot of dry material is added, it is important to add water. Paper does not hold moisture at all, as well as being devoid of nitrogen and micro-nutrients, so we try to keep it out of our piles in large amounts.
Oxygen is necessary for the bacteria in the pile. The difference between compost and landfill is that landfills don't have oxygen. If the pile is smelly, there's a good chance it needs to be aerated by turning it or poking holes in it.
I have a big bag of banana peels/apple cores/dead garden plants/tea bags/coffee grounds. What should I do with them?
Well if you have a backyard at home, you should consider a home compost pile! Otherwise, the Concho piles accept donations like this. Our piles are a little bit picky though. First, make sure to take all the stickers off your fruits. Those little stickers don't break down. We want to keep our compost trash free. If the garden plants are big, be sure to cut the plants into small pieces. When adding to a pile, be sure to mix the materials in to the pile. If we leave stuff sitting on top, it just dries out or attracts flies.
I have a big bag of newspapers/cardboard/”compostable” plastic/large sticks/whole pecans/metal/wrappers/”compostable” plates and cups. What should I do with these?
Please do not add these things to our piles! Adding metal and plastic to a compost pile is practically littering. Newspapers and cardboard are technically biodegradable, but they do not hold much moisture or have any nutritional value. Better to recycle your paper and cardboard. Industrially manufactured products with the label “compostable” take a long time to decompose and are only suitable for industrial compost facilities. Austin is working on curbside compost collection.
How can I help? How can I learn more?
Come out to the garden on a workday, every Sunday from 9:30-12:30. We are also having another compost class on March 24th, so if you missed the first one you should definitely attend the next one! More reading about compost can be found here or at the public library.