Compost Improves Plant Health
It is safe to say that adding compost to your soil is one of the best things you can do to keep it healthy. Read on to learn how using compost can be a good supplement to topsoil by adding the beneficial nutrients plants need as well as helping improve the soil structure.
In a nutshell, the key benefits of compost when mixed with topsoil and native soil are:
- Compost adds nutrients that are available for plants to use over time (over months or years).
- It helps retain water and nutrients from fertilizers in soil.
- It makes soil more porous and easier to dig.
- Supports earthworms and beneficial microorganisms.
With each growing season, nutrients are used up by plants and many gardens often get compacted over time. In addition, winter rains can relentlessly wash nutrients out of soil while making its pH more acidic. Adding compost helps with all these issues. Besides adding the nutrients the plants need, compost will make soil easier to work with and less likely to erode. And compost has this uncanny ability to neutralize both acidic and alkaline soils to put them in a range that most plants prefer. Adding compost is indeed one of the best things you can do to create healthy soil!
There are different varieties of compost which can be confusing since not all compost is good for every planting need. Here are some of the most common types.
- Bagged General Purpose Compost – This is commercially made compost found in bags at garden supply stores. It is made under controlled conditions with the right amount of moisture and aeration so that it heats up enough to kill off weed seeds and pathogens, so there is a certain implied guarantee that these products will be safe to use in your garden. Many of these products are considered general purpose although they may not be appropriate for all plants (particularly young seedlings). Often the ingredients that are used to make the bagged compost comes from limited sources so manufacturers add fertilizers to increase their nutrient content. At $6/cf, this can be expensive if you need a lot of it.
- Mushroom Compost – This is another bagged commercial product consisting of straw, manure, gypsum, among other things. It drains well due to the high straw content and is a good source of organic material for long term benefits in the garden. It is not as nutrient-rich as other composts so mixing with other compost and/or organic fertilizers will help for vegetable gardens and other plants with high nutritional needs. The gypsum in it tends to make soil more alkaline making it good for balancing out acidic soils. But avoid using mushroom compost on acid-loving plants such as berries, rhododendrons, camellias, etc.
- Homemade Compost – The main benefit of home compost is you know what’s in it! It is also free, and many backyard compost bins can produce several cubic feet (or even yards) each year. Also, if you are able to use a wide variety of different materials from your yard and kitchen, the nutrient quality will be superior to other compost sources. There are a couple of things to watch out for when making your own compost. Usually the finished product will have some larger chunks of wood or other material that affects the compost’s texture (but not its quality). If you prefer a smoother product, you can use a sifter to separate out the larger pieces. Also be careful about using compost before it is ready. If your compost is still actively breaking down the source material, it could rob nutrients (particularly nitrogen) from your garden plants. You can tell the compost is ready to use when it is dark and crumbly and has a pleasant earthy smell. Another issue with home composting is the piles often don’t get hot enough to sufficiently kill all the weed seeds and pathogens as in the commercial products. It is for this reason at the community garden we advise our gardeners to not throw weeds or diseased plants into the compost bins.
- Vermicompost (Worm Castings) – This is the byproduct of worms eating and excreting organic materials such as kitchen scraps. It is nutrient-rich, biologically active, and helps condition the soil. Being water soluble it is easy for plants to absorb and can be used as a slow-release organic fertilizer. You can have a home worm bin to make your own vermicompost, and it is also available in bags online or in some garden supply stores (although rather expensive).
- Manure Compost – This is usually made with chicken, cow, or horse manure from farm or ranch animals. Manure is widely available for companies to make compost on a large scale and you can find it bagged at garden supply stores. The manure is aged, or left to decompose, so it can be used as an effective nutrient-rich amendment for gardens. It has a high nitrogen content which can burn some plants so be sure to mix it well with your topsoil. Manure (or manure compost) can be added to your home compost pile to help heat it up to speed the composting process and to potentially get it hot enough to kill off the weed seeds. Never use waste products from animals that eat meat (such as dogs, cats, etc.) as this manure contains unhealthy pathogens for a vegetable garden.
Once you have decided on which compost works best for your need, it’s time to use it! Every gardener I speak with seems to have their own ways to incorporate it into their garden. You may have your own methods, but I will share some general guidelines. When amending soil in the spring, cover the garden bed with 1-2 inches of compost along with any other amendments you would like to add and work it in to the top 3-6 inches of soil. For brand new garden beds with weak soil, add an extra inch or two of compost. On the other hand if you have an area with healthy soil that has been regularly amended with compost, you may use less.
In vegetable gardens it is helpful to add a handful of compost in the hole when planting veggie starts. You can also sprinkle compost on top of the soil during the growing season to give your plants an extra boost. As you water, the extra nutrients will work their way down to the roots.
Landscape plants will also benefit from compost. You can add an inch or so of compost to existing flowers, shrubs, and trees by covering the soil as a mulch. For new plantings, mix compost with the native soil in a 50-50% mix to give plants a nutritional boost.
And remember, besides simply adding nutrients, your plants will benefit with stronger root development, more drought tolerance, and improved disease resistance. Healthy soil makes for healthy plants!
If you would like to get started with your own compost pile, this article should be helpful. https://www.epa.gov/recycle/composting-home
For questions about this article or how to get involved in the community garden, please contact us at info@gardenbytheseaoceanshores.org.
This article was originally printed in the Ocean Observer, May 2023.
