Compost is organic material that has decomposed through a natural process into a nutrient-rich, soil-like substance. Also known as “black gold,” it is commonly used as a soil conditioner and natural fertilizer in gardening, landscaping, and farming. Compost is made by combining organic waste — food scraps, yard waste — and allowing microorganisms, fungi, and other decomposers to break it down over time.
What Does Compost Do for Plants and Soil?
While compost is an excellent way to reduce waste from your kitchen and yard, it is more than just decomposed organic matter. This material, which looks like crumbly dark soil, is a powerhouse of nutrients, organic compounds, and beneficial microorganisms that improve your soil and support healthy plant growth.
Benefits for Plants
- Provides slowly-released nutrients: Compost contains essential nutrients like nitrogen, phosphorus, and potassium, along with calcium, magnesium, and iron. These nutrients are slowly released from the compost over time, providing a steady supply to plants.
- Improves growth: Beneficial bacteria and fungi in soil help improve root health, allowing the plant to take in nutrients and water better. Compost also contains humic acid and other organic compounds that promote growth.
- Reduces disease: Compost introduces beneficial microbes into the root zone that compete with harmful pathogens, creating a healthier growing environment.
- Enhances stress resistance: Plants grown in compost-enriched soils are often more resilient to environmental stressors like drought and extreme temperatures. This is likely due to organic compounds acting as plant growth regulators, boosting defense mechanisms.
Benefits for Soil
- Improves soil structure: Compost helps bind soil particles into clumps known as aggregates. This crumbly texture improves aeration and drainage. In soils with a lot of clay, this aggregation helps prevent soil compaction; in sandy soils, it improves water retention.
- Boost microbial activity: Compost introduces beneficial microorganisms that help break down organic matter, making nutrients more readily available to plants. These microbes also help create a healthy, thriving soil ecosystem.
- Increases water retention: Compost absorbs water, improving soil’s water-holding capacity. This increase in water retention helps plants endure periods of low rainfall or infrequent watering.
According to the City of Ankeny, Iowa, “A hundred pounds of average soil (a 1×10-foot row tilled 6 inches deep) with a pound of compost mixed in will hold an additional 33 pounds (4 gallons) of water. Take the organic content to five pounds, and that hundred pounds of soil will hold nearly two hundred pounds (25 gallons) of water!”
- Reduces nutrient leaching: Compost is rich in organic matter, which has a high cation exchange capacity (CEC). A higher CEC means your soil can hold more nutrients, reducing leaching potential.
- Balances soil pH: Compost buffers changes in soil pH because of its organic matter content. It can also help neutralize acidic or alkaline soils, making them more suitable for plant growth.
- Reduces erosion: Compost helps prevent soil erosion from wind and water runoff by improving soil structure and water retention.
What Can Go Into Compost?
Four main things are needed for a successful compost pile: brown materials, green materials, water, and oxygen. Brown and green materials are the waste products from your home, yard, and garden, and they must be added in specific amounts to keep the carbon and nitrogen correctly balanced in the pile.
The specifics on what you can put in your compost bin are a little more in-depth, but in general:
- Brown materials are carbon-rich items that provide energy to the microorganisms in the pile and give compost its light, fluffy body. Typical brown items are wood-based or fibrous: dry leaves, branches, stems, sawdust, tree bark, shredded newspaper, corn stalks, wood ash, and pine needles.
- Green materials are nitrogen-based waste materials that provide amino acids and proteins needed for bacteria and fungi to do their job. Excellent nitrogen-rich materials include food scraps, coffee grounds, green leaves, and grass clippings.
Pro Tip: A simple rule of thumb is to keep the compost pile approximately 2/3 “brown” and 1/3 “green” materials.
Where Can You Spread Compost?
One of the great things about compost is that you can use it in many ways in your yard. You can spread it anywhere you have soil or are growing plants.
- Gardens: Cover the bare soil with 2 to 4 inches of compost to improve water retention, promote healthy plant growth, and minimize soil loss from erosion.
- Lawns: You can topdress existing lawns by spreading a thin layer of compost over it or mix it into your soil before seeding or laying sod.
- Around trees and shrubs: Spread a few inches of compost on the bare soil at the base of your trees and shrubs to improve water retention.
- Pastures: Topdress pastures similar to lawns to improve soil health, structure, and water retention. It can also cut down on weed seed germination.
- Hillsides: Add a layer of compost to sloped areas prone to erosion. The compost improves water infiltration (reducing runoff that causes erosion) and stabilizes soil.
- Houseplants: Mix compost with your potting soil to create a rich, fertile growing medium. After planting, add a thin layer of compost to the top of the potting soil.
My Tip: I’ve found over the last 20-some years of gardening and planting flowerbeds, that if you are limited on what you can do — whether because of budget constraints or time — and want to improve your soil, the best thing to do is add compost.
Some people often choose manure because the bags are cheaper, but it has drawbacks. First and foremost is you can’t guarantee it has been aged properly. Manure that is still fairly fresh may contain harmful bacteria and pathogens, may be full of weed seeds, and depending upon the animal source, it may be high in nitrogen and potentially burn your plants.
High-quality, “finished” compost has been properly aged, offering the most benefits to your soil and plants. After it goes through the entire process, a cycle including high temperatures that naturally occur within the pile, the compost will be free of harmful pathogens/bacteria and weed seeds. It also has a lower nitrogen content, so it won’t damage your plants.
FAQs About Compost
Yes, applying too much compost can have adverse effects and harm your plants. An abundance of compost can cause high levels of nitrogen and phosphorus, disrupting growth. You’ll see vigorous foliage growth versus fruiting — which is problematic in tomatoes, peppers, etc. — and the high phosphorus can impede the uptake of calcium, magnesium, and iron.
While compost is helpful, you want to mix it with another growing medium (soil, potting soil, peat, etc.) for growing plants. Straight compost may be high in nitrogen and phosphorus but lacking in other essential nutrients. It also can create waterlogged conditions as it retains water too well. Plus, since it doesn’t have the same structure as soil, it can become compacted when wet.
No, compost and manure are different, although they both can improve soil health. Compost results from the decomposition of organic material by microbes, earthworms, and other microorganisms. Manure is animal waste that has not been decomposed yet. It can help soil fertility and plant growth but must be carefully applied as it can be too intense or “hot” if not appropriately aged.
Compost Can Help Your Yard, and So Can We
Compost is an excellent addition to your lawn, garden, flowerbeds, and landscaping, but it isn’t a miracle cure. You still need to keep up with other proper maintenance. Reach out to LawnStarter, and we’ll put you in touch with a lawn care professional to help with your grass, trees, or landscaping. A local pro can take care of the maintenance needed to keep everything looking its best.
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