What is Compost?
Compost is the poster child for organic matter. It is the end product of the decomposition of organic matter. It can be any kind of organic matter, which includes garden waste, kitchen scraps, leaves, grass clippings, straw, even manure.
Compost is not particularly high in essential nutrients, (N-P-K), and is considered a soil conditioner rather than a fertilizer, but it creates a better soil and makes nutrients more accessible to plants.
Compost makes a valuable soil amendment because it:
- Can improved soil structure
- Aids in necessary microbial activity in the soil
- Attracts beneficial insects such as earthworms
- Can suppress several soil born diseases
- Holds its nutrients in organic or slow release form, allowing for availability throughout the growing season.
By the time the compost cooking process is complete, weed seeds, fungus spores and other undesirable elements that may have gone into your compost bin, should no longer be viable. Finished compost looks like rich soil. It’s dark and crumbly with an earthy smell.
How to Make Compost
While there are many methods of composting and many composting bin styles, there is no best method. The important thing to remember is that you can never add too much compost to your soil.
There are 2 basic approaches to making your own compost: active and passive:
Passive composting is the "Compost Happens" school. All you need to do is pile up your organic matter and wait. It can take a few years to fully decompose, but eventually it will. However it may never heat up enough to kill off weed seeds and spores.
Active composting requires varying degrees of effort. Truly active composting involves being somewhat precise with the layers you add to your compost pile and turning it regularly. Something like this:
- Make a pile or use a bin that is at least 3 ft. by 3 ft.
- Start with a 3 - 6 in. layer of brown material (hay, straw, dry leaves...)
- Add a 9 - 18 in. layer of green material (plant debris, kitchen scraps, grass clippings...) on top of the brown layer
- Water until the pile is damp.
- Repeat the layers until the compacted pile is at least 3 ft. high. If it is smaller than 3 ft., it won't heat up.
- Turn the pile every couple of weeks, so that it is uniformly mixed.
- When the pile reaches its full size, cover it with a tarp to keep the nutrients from washing away and to prevent it from getting too wet.
- When it is crumbly and resembles soil more than debris, it's time to sift out the large pieces that have not yet decomposed and start using your compost.
- Repeat. Ideally you'll have several compost piles going at once. One that is ready to use, 1 that is full and in the decomposing process, and finally 1 that you are still adding to. The 3 bin system in the photo accomplishes this.
As with anything in nature, there are a lot of variables, so there is no perfect method of composting. Three parts green to 1 part brown is a good rule of thumb to follower. However if you're a "let it rot" kind of composter, you'll still end up with a good compost.
What Can Go into Compost
Any type of organic material that has not been treated with herbicides or pesticides. Some common materials include:
And eggshells, which are neither green or brown, but still add some calcium to the mix
What to Keep Out of Your Compost
While it is advised that you keep weeds, especially perennial weeds, pesticide treated material and diseased plants out of your compost bin, most every other form of plant material is fair game.
Other materials to avoid include: bones, meat and fish scraps, pet manure
What to Look for If You are Purchasing Compost
You can buy compost by the bag or by the truckload. Either way, it's good to know the source.
Bagged Compost: The problem with bagged compost is that you don't really know what you're getting until you bring it home and open the bag. Many times compost by the bag is composted manure, which is usually fine. To be on the safe side, look for the word "organic" on the label. That would offer some guarantee that whatever ingredients were used were not contaminated or something you would not want in your garden, like sewage, heavy metals, or pesticides.
Bulk Compost: This is definitely the cheapest way to purchase compost. Just as important, you can see what you're getting before you get it home. Don't be afraid to ask what they are using to make their compost and if it is organic.
I strongly recommend you check out the compost before ordering. It should smell fresh and earthy and not be so wet it drips when you squeeze a handful. Ideally it will still be warm, so you'll know that it's freshly made.
How to Use Compost
Compost can be added to your gardens at anytime, either turned into the soil or used as a mulch or top dressing for established plants. You can add it just before planting time or amend your beds in the fall and let the natural freezing and thawing process work it into the bed.
How much compost your soil needs will depend on the quality of the soil. The more you add, the better your soil will become. It's really hard to go wrong adding compost, but it's not a one-time fix. You'll need to amend your beds annually, which is why gardeners always say there is never enough compost.