Skip to main content
  1. Home
  2. Gardening

Want to know what organic matter does in gardening soil? Here’s the scoop

Stacey Nguyen
By

Fortifying your soil with organic matter is a planting basic for growing crops, no matter if you’re working on an agricultural scale or tending to a modest garden. From dead leaves to chicken manure, there’s a wide range of materials that can break down into soil-nourishing organic matter. Ahead, we’ll go over all you need to know about organic matter and its purpose in your garden soil.

Person tending seedlings in soil
Image used with permission by copyright holder

What is organic matter in soil?

In a nutshell, soil consists of minerals, organic matter, air, and water. About half of soil is air and water, while the other half is minerals, such as sand, clay, and silt. Then, anywhere between 2 to 10% of soil is organic matter. Organic matter is composed of many things; however, it generally comprises dead and living things in various states of decomposition — this includes plants, animals, and microorganisms.

Gloved hands holding soil with different colored balls of fertilizer in it
Image used with permission by copyright holder

What are the three types of organic matter?

The three types of organic matter are active organic matter, passive organic matter, and slow organic matter. Here’s what to know about each type.

  • Active organic matter: Active organic matter can take anywhere from months to years to decompose. It includes plant and animal residue that’s rich with microorganisms. This organic matter contributes to soil fertility by releasing nutrients, such as nitrogen. 
  • Passive organic matter: Passive organic matter, also known as “humus,” has already been decomposed. While it provides little food for soil organisms, it gives soil its dark color and contributes to soil structure.
  • Slow organic matter: Slow organic matter refers to matter that can take decades to break down — this includes materials like bones.
Person putting mulch around a plant with yellow flowers
ronstik / Shutterstock

Why organic matter is necessary for soil

Although it’s usually only a small percentage of soil, organic matter delivers many critical benefits to plants. Here are just a few of its top contributions to soil:

  • It provides nutrients for plants as microbes break down and release nutrients, such as nitrogen and phosphorus. 
  • It stores nutrients in soil and increases soil’s cation exchange capacity, or CEC. Organic matter has a negative charge, so it attracts positively charged cation particles, such as calcium and magnesium. 
  • It helps sandy soil retain water and clay soil drain excess water. As a result, organic matter allows plants to properly access water and nutrients as it improves soil structure.
  • It keeps plants healthy so they can resist pests and diseases. Organic matter is food for beneficial microorganisms that help fight microbes that cause soil diseases and improve plant growth.
Recommended Videos

Can soil have too much organic matter?

Of course, you can have too much of a good thing. Excess nutrients can damage plant roots and pollute waterways with toxic algae blooms. When tending to your garden, avoid overfertilizing your plants.

Related

Hands holding compost

How can I make my soil more fertile?

In a garden landscape, aim for at least 2% organic matter. In a garden landscape with fruits and vegetables, you want to get that number even higher, around 5 to 10%. You can usually take a soil sample and test it for organic matter by sending it to a soil testing lab.

So what kind of garden activities decrease your soil’s organic matter composition? Picking crops depletes organic matter as you take out soil nutrients. Tilling also tends to break down organic matter faster by introducing oxygen. Soil erosion caused by harsh winds and rainfalls can also impact your soil’s reserve of organic matter as it displaces soil and the organic materials in it. These activities are just the tip of the iceberg, so regularly fortify your soil with organic materials to keep it rich and fertile.

Replenishing your soil with organic matter only takes a little bit of legwork. At the beginning of the growing season, you can increase the organic matter in your growing medium with soil amendments, such as compost, manure, and worm castings. Additionally, it helps to top-dress your crops with mulch and fertilizer, which can break down into organic matter. You can likewise grow cover crops and perennial grasses — the foliage and roots of these plants can also eventually break down into organic matter.

Although just a sliver of your soil composition, organic matter can make or break your garden crops. From holding onto nutrients to improving soil structure, it provides a wide range of benefits to your garden bed’s growing medium. You can boost your soil’s organic material by adding a bit of compost or manure. Many different organic materials can break down into organic matter, providing you with rich, fertile soil to nourish your plants before you know it. 

Editors' Recommendations

Topics
Stacey Nguyen
Stacey Nguyen
Contributor
Stacey's work has appeared on sites such as POPSUGAR, HelloGiggles, Buzzfeed, The Balance, TripSavvy, and more. When she's…
Choosing the best grass seed for your lawn – what you need to know
Factor in these tips when deciding on grass seed
Manicured Bermuda lawn

Growing grass from seed is an affordable way to start a lush, healthy lawn. But you need to start with the right seed. What is the best grass seed? It depends on where you live, the conditions in your yard, and how you ultimately want the yard to look. Cool-season grasses give a soft, deep green appearance, while warm-season grasses are known for dense green growth and uniform tan coverage in winter. There are several kinds of each to choose from. Read on to learn how to choose grass seed for your unique situation.

1. Choose cool-season or warm-season grass
Cool-season lawn grasses grow best when daytime temperatures are in the 60s and 70s, and night temperatures are in the 50s. They are primary choices for northern landscapes, where they look great from right after the snow melts in spring until the first hard freeze of fall. In the lower Midwest and upper South, these grasses offer an evergreen alternative to the warm-season grasses that go brown in winter. Cool-season grasses suffer damage during extended and extreme heat and drought and must be reseeded periodically to repair damage.

Read more
Do tomatoes need full sun to thrive? What you need to know
How different levels of light impact your tomato growth
A cluster of ripened tomatoes

Do tomatoes need full sun? How many hours of sun do tomatoes need? Well, tomatoes are one of many edible crops that have a wide range of varieties. Each one can vary in size and color, from the familiar cherry tomatoes on salads to the larger ones used for slices on burgers and sandwiches.

Some varieties, like Roma tomatoes, are much better for homemade sauces than for fresh consumption — but every tomato needs diligent care. The best thing you can do to ensure you get a flavorful, fruitful harvest is to provide your tomatoes with the proper care. Sunlight is especially important for this warmth-loving crop.

Read more
Make sure your hydrangeas have the best blooms by pruning them properly
The right way to prune hydrangeas
Purple and blue hydrangeas

Hydrangeas are beautiful and interesting flowers. They change color based on the pH of the soil, making them a unique and fascinating addition to most gardens. They’re easy to grow and propagate, make wonderful cut flowers, and can even be grown in containers. If you want to add them to your garden, then you'll need to know how to prune hydrangeas. Although cutting a plant can be intimidating, it's surprisingly simple once you know what to do. This comprehensive guide will help you get started.

Why would you want to prune hydrangeas?
To keep your garden space looking beautiful, it's a good idea to stay on top of pruning your hydrangeas. Hydrangeas can grow fairly quickly, averaging a growth rate of 2 feet per year. Pruning your hydrangeas helps you shape your bush and remove dead or crossing stems.

Read more