What Nutrients Are in Compost?

Compost is a rich blend of organic matter, such as food waste, grass clippings, and coffee grounds. Those ingredients may not sound like much on their own, but together, they can be a nutrient-rich powerhouse that enhances your soil’s structure and composition. Keep reading to discover exactly what nutrients compost contains and how to use it in your garden.

What Is Compost?

While compost is not on the same level as a synthetic fertilizer, it’s still a rich blend of nutrients that enhances the soil and supports beneficial microorganisms and earthworms.

There are two types of materials that make up compost:

• Brown materials: These include dried leaves and wood chips rich in carbon.
• Green materials: These include grass clippings and food scraps rich in nitrogen.

With time, warmth, and a little moisture, the brown and green materials degrade into a brown soil-like substance.

What Nutrients Are in Compost?

Compost is a treasure trove of nutrients for plants. Since no two compost bins have the same contents, the exact amount of nutrients will also vary from one batch to another.

Macronutrients

Macronutrients in compost break down slowly, and plants absorb what they need gradually, reducing the risk of nutrient burn from overfertilization.

Compost will typically be rich in these main fertilizer nutrients:

• Nitrogen: Promotes lush foliage
• Phosphorus: Strengthens roots
• Potassium: Contributes to overall plant health and disease resistance

Micronutrients

Micronutrients play important roles in photosynthesis, enzyme and chlorophyll production, and stress resistance. Compost can have these micronutrients and trace elements not typically found in chemical fertilizers:

• Sulfur
• Carbon
• Magnesium
• Calcium
• Boron
• Copper
• Iron
• Iodine
• Zinc
• Manganese

Humic Substances

Compost contains humic substances, which are formed by the biochemical reactions of microorganisms decomposing plant matter. Humic substances contribute to the brown color of soil and decaying plant materials. They also provide numerous benefits to soil, such as boosting nutrient retention, improving water-holding capacity, and serving as a food source for microbes.

What Should I Compost?

A good compost needs a balance of brown and green materials. Brown materials include dried leaves, hay, cardboard, and non-glossy paper. Green materials include fruit and vegetable scraps, grass clippings, coffee grounds, and manure. Avoid adding meat, dairy products, or oily foods to your compost pile. Those can create foul odors and attract pests.

Once your compost is ready, you may want to send samples of the finished product for compost testing (similar to a soil test) to learn how your compost measures up. Compost testing will tell you the carbon-to-nitrogen ratio, pH, and nutrient analysis, along with particle size and moisture content. You can find information about compost testing at your local agricultural extension office.

What Are the Benefits of Using Compost in Your Garden?

Using compost encourages plant growth, but there are many more reasons why you may want to use it in your garden. These are just a few:

• Improved soil structure: Compost can help loosen compacted soil so roots spread out and breathe easily. It also adds stability to loose soil for better moisture retention.
• Improved soil chemistry: Compost helps regulate soil pH for a healthy growth environment.
• Better nutrient retention: One of compost’s superpowers is its ability to hold onto nutrients such as nitrogen, phosphorus, and potassium. While it may not pack the same punch as chemical fertilizer, it’s slower to release and often applied in larger amounts, so it makes up for the difference over time.
• Natural pest suppression: Compost’s beneficial microorganisms compete with pathogens to create a more balanced soil ecosystem, which can reduce the need for chemical pesticides and fungicides.
• More organic matter: Organic matter attracts earthworms and beneficial insects.

How Can You Use Compost in the Garden?

Compost has several uses in the garden, such as the following:

Planting and Mulching

One of the easiest ways to use compost in your garden is to mix it directly into the soil when you plant new plants. Spread a 3 to 4-inch layer over the soil and work it in as deeply as you can. If you’re planting from seed, add a ½-inch layer of compost around the stem once the plant starts to grow. During the summer, you can also use compost as mulch or top dressing for your beds.

Lawns

For new lawns, apply a 1 to 2-inch layer before seeding or a 1/4 to ½-inch layer after seeding. Once the lawn has grown in, a 1/4-inch top-up can give it a seasonal boost.

Container Gardens

If you have a container garden, use organic potting soil and compost in equal parts to make a nutrient-rich blend. Consider screening your compost to remove sticks, pits, and other large debris. This also makes the compost fluffier and enhances its quality.

Potted Plants and Windowboxes

Create a potting blend for potted plants and windowboxes with equal parts compost, sand, and loam. Top the pots off twice per year by adding another inch of compost.

Flowering Bushes and Fruit Trees

Incorporate compost into the soil when planting flowering bushes and fruit trees. Once established, spread compost around the base.