Skip to main content
  1. Home
  2. Gardening

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

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
Singkham / Shutterstock

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…
Your complete sago palm maintenance guide
Grow a sago palm to add a tropical flair to your home
A small sago palm in a pot designed to resemble a wicker basket. It sits on a table of light wood, next to a bookshelf of the same wood. The wall behind it has a dacorative pink, blue, and white triangular pattern.

Sago palms may not be true palms, but they are just as gorgeous. However, with these subtropical houseplants, you won’t have the same kind of look offered by those tall trees. Instead, the green fronds grow directly from the trunk without branching out. Sago palm maintenance is fairly simple, relying mostly on proper growing conditions. Adding this lovely houseplant to your collection is an excellent way to bring the tropics to your home. If you want to grow your own today, this guide will explain everything you need to know to help it thrive!
Care requirements for your sago palm

Because they’re native to tropical regions, sago palms prefer to be in warm, humid environments. This is why, for the most part, they’re grown as houseplants outside of these areas. Sago palms grown indoors should be protected from any drafts or air flowing from heating and AC units as the extreme shift in temperature can cause damage.
Light
Sago palms prefer bright, indirect lighting and shouldn’t be placed in direct sunlight. Direct lighting, especially on hot summer days, can cause sunburn damage and result in wilting leaves. As a houseplant, sago palms will favor east-, west-, and south-facing windows so long as they receive a lot of lighting throughout the day. Keep in mind that too much shade will also cause adverse effects, most noticeably spare foliage.
Soil
Like most houseplants, sago palms need only well-draining soil (and of course, a pot with a drainage hole for excess water to escape through)! There are potting mixes made specifically for palms grown in containers, and although the sago palm isn’t a true palm, this should do the trick.
Water
As a tropical plant, sago palms prefer moderately moist soils. They can tolerate some drought, but not very well. Proper sago palm maintenance requires watering the plant whenever the soil is dry to touch; however, be mindful of how much you’re watering to avoid soggy soil and leaving your plant susceptible to root rot.
Diseases and pests to be aware of

Read more
What does NPK mean when it comes to fertilizing plants?
Your guide to the main nutrients in the NPK ratio for robust plant growth
A gardener fertilizing a young plant

Just like humans, plants need food to stay healthy and strong. Fertilizers give plants full-sized leaves, healthy roots, and vibrant flowers. Without sufficient soil nutrients, plants will grow very slowly, developing weak stems and pale leaves. Fertilizer helps make up for what the soil may be lacking, so that your garden has a balanced diet to grow and thrive.

When choosing your fertilizer, you might have noticed something on the label called an NPK ratio. If you're wondering what that means and how to use it to choose the best fertilizer for your plants, we have the answers.
What is NPK's meaning in plant fertilizing?

Read more
What you need to know about growing the delicate bleeding heart flower
A care guide for the bleeding heart flower
A branch of pink bleeding heart flowers

Bleeding heart flowers are uniquely stunning, but growing them can be tricky. They get their name from their unique flowers, which dangle off each branch. The flower has a heart-shaped top, with a smaller droplet shape beneath that, giving the plant the appearance of a row of bleeding hearts. If you want to try growing these gorgeous pink flowers in your garden, we’ll show you how. Here’s everything you need to know about growing and caring for bleeding heart flowers.
Planting bleeding heart flowers

Start by choosing a planting site in partial shade and well-draining soil. Direct sunlight can burn delicate bleeding heart flowers, especially in hot climates or during the hottest part of the day. In cooler climates, bleeding heart flowers can withstand more sun, but getting the balance right can take some trial and error. In general, aim for morning sun and afternoon shade. Well-draining soil is important as well, since bleeding heart flowers have sensitive roots. They can develop root rot or crown rot if left in standing water.

Read more