Organic Garden Soil: The Importance Of Soil For An Organic Garden

A successful organic garden is dependent upon the quality of the soil. Poor soil yields poor crops, while good, rich soil will allow you to grow prize-winning plants and vegetables. Here are a few ideas for adding organic matter to the soil to help provide the nutrients it needs for an abundant harvest.

Organic Soil Amendments

Adding organic matter to the soil for organic gardens is crucial to the health of your plants. Here are some common organic soil amendments for creating healthy garden soil.


It doesn’t matter which article you read or which organic gardener you talk to, they will all tell you the same thing; an organic garden begins with compost. Compost is simply deteriorated, rotten organic matter. It can be made with household cooking scraps, leaves, grass clippings, etc. The longer your compost bin cooks, the better the resulting compost will be. Most gardeners recommend at least a year.

Compost is worked into the existing soil before spring planting and can be added later in the summer if you plan a fall garden. The nutrients from the compost will help ensure strong healthy plants. Healthy plants are less likely to be devastated by bugs or disease.


Manure is another popular fertilizer among gardeners for adding organic matter to the soil. The droppings from cows, horses, goats, rabbits, and chickens are all considered to be viable manure for your garden. Manure can be purchased from garden centers, or if you are lucky enough to live near a rural area it can be purchased directly from the stock owner at a more reasonable price.

Beware of putting fresh manure on your garden space as it can burn the plants. This is best applied in late fall after all plants have been harvested or added to your compost pile to age.

Organic Soil Fertilizers

There are a number of other organic soil fertilizers you can add to the garden. Fish emulsion and seaweed extract, while expensive, can do wonders for your soil. Bone meal is another, somewhat cheaper, alternative.

Comfrey is yet another option, which in addition to manure or compost, can be given to plants in the form of tea. All of these options provide much-needed nutrients, especially if compost or manure is not available.


After your soil has been prepared, you are ready to plant. If you are like most gardeners, you will already have many plants started, like tomatoes and peppers. Once you have them spaced the proper distance in the garden, your next step is to mulch.

Mulching is the practice of using straw, hay, or even shredded newspaper around the plants in order to keep weeds from overtaking your garden. Most gardeners apply a layer of mulch all around the plants and in the walkways to deter the growth of unwanted plants.

For plants you start directly from seed in your garden, you should wait until they have broken the ground before you mulch. This makes it easier to thin the plants to the proper distance apart and can allow you to see which plants appear to be the strongest. Once thinned, apply mulch as you did for the seedlings.

At the end of the growing season and following the harvest, till the mulch directly into your garden plot. Tilling will help the soil retain much-needed moisture and keep the organic garden soil workable.

Healthy Soil for Organic Gardens

The soil in some locations can be so poor that topsoil will need to be purchased in order to even begin a garden. You can have your soil tested by taking a sample to your local county extension office. They can tell you what nutrients your soil is missing and give you further guidance on how to improve the type of soil you have. Generally, there is no charge for this service.

Keeping your soil healthy and nutrient-loaded without the use of chemical fertilizers is a bit more work. Yet, at the same time, you know exactly what is in your garden, and the results will be quality fruits and vegetables that you can eat without worrying about chemical residue. Trust me, nothing tastes better than biting into a red, ripe tomato right off the vine when you finish your morning weeding.

Organic Gardening Soil Amendments

Organic gardening soil amendments are materials added to the soil to enrich the soil fertility and structure.

There are three methods of adding organic gardening soil amendments to your soil.

  1. You can cultivate the amendments directly to your soil. The nutrients are released as the material decomposes which will occur quickly when they are broken down which the tilling will do.
  2. Another method is laying the material on the soil as a mulch where it will rot into humus over time. This is probably the easiest method, but takes the longest to decompose.
  3. You can make your own compost and then add it directly to your garden beds. Making compost can be done quickly over several weeks or it may take longer depending on how well you want to manage it.

All three methods for adding organic gardening soil amendments can be used in your garden or choose any one method that works best for you.

Adding in the organic matter will increase your soil fertility giving you healthier vegetable plants and a more productive harvest.

Where does all of this clay come from?

Just like plants and animals, there’s actually a scientific way to classify soils. Knowing which of the 12 soil orders your soil belongs to can go a long way in helping you know how to plan your garden. Most of Durham County, and more broadly the southeastern part of the United States, has soils referred to as Ultisols. Ultisol soils are produced when heavy rain leaches many nutrients from the soil and warm weather prevents organic matter accumulation. The soils created under these conditions are highly weathered, acidic (low pH), and rich in clay (1).

Clay is the smallest of the three major particles of soil, with silt being slightly larger, and sand having particles large enough to see with your bare eyes. Relatively speaking, if sand particles were as large as basketballs, many clay particles would be roughly the size and shape of grains of rice. This helps explain why clay holds water so well – not only are the particles very small, but they also fit together closely because of their flattened shape (imagine draining water through a barrel of basketballs versus a bucket of rice). The proportion of clay to silt to sand is described as the soil’s texture.

Our clay soils make gardeners work a bit harder than gardeners in other parts of the country. When wet, the clay is slippery muck when dry, it cracks and hardens into concrete. The clay isn’t all bad though: clay holds many plant nutrients extremely well, meaning our plants are well set up if we can just improve our soil structure.

The image on the left shows a close-up of sand particles which appear grainy as seen by the naked eye. The right shows the platelike texture of clay visible only under a microscope. From the North Carolina Extension Gardener Handbook.

Organic Matter

  • Soil organic matter (OM) is made up of living, dead, and decomposing plants, small animals, and microorganisms. Materials we think of as dead, like brown, dried up leaves or banana peels, are teeming with microbial life. There can be a billion microorganisms in a teaspoon of compost or soil!
  • Adding organic matter improves soils high in clay or sand.
  • Soils high in OM retain more moisture, have a crumbly structure that resists soil compaction, and contain a reservoir of nutrients that are slowly released over time.
  • OM improves soil aeration, water drainage, root growth, and biological activity.
  • Compost and pine bark fines are good peat moss substitutes (a mined and non-renewable natural resource).
  • Most garden and landscape plants perform best when the soil organic matter level is at least 2% (the goal for vegetable and flower beds should be 5%-10%). These soils are loose, easy to prepare for planting seeds and plants, and have a large number of earthworms.
  • Organic matter is measured by weight, not volume. Most soil testing labs include organic matter in their basic soil test.

How to Re-Amend Soil for Reuse

If you are emptying small pots and containers, grab a tarp to dump the soil on. Once you have all of the soil you would like to re-amend dumped onto the tarp, it is time to add the missing nutrients back into the soil.

For those re-amending a plot or raised bed, you do not need to move the dirt! Simply spread the missing ingredients on top of the soil. Then, lightly overturn the area to mix the amendments into the top six inches of soil. There is no need to mix deeper than six inches below the surface, as mixing deeper will disturb microbes and organisms living in these soil layers, effectively doing more harm than good.

Now it is time to add the goodies to your soil, be it in a plot or on a tarp!

We are using two example amounts for our explanation. The first column lists amendment measurements for a smaller, single, 15-gallon pot. The second column lists measurements for a larger, three-yard plot of soil. Depending on the amount of soil you are re-amending, the recommended inputs will vary.

To start, gather the following amendments in the appropriate quantities for your application:

Single 15-Gallon PotRoughly 3-Yards of Soil
½ to 1 Cup Neem Cake 30 to 40 Cups Neem Cake
½ to 1 Cup Crustacean Meal 30 to 40 Cups Crustacean Meal
½ to 1 Cup Kelp Meal30 to 40 Cups Kelp Meal

Please note that you may find yourself needing more or less of the above nutrients depending upon your soil and the crops you plan to grow next. Additionally, you may see best results after adding more amendments to the soil, such as the optional ones mentioned below.

Optional Amendments:

½ to 1 Cup Gypsum 30 to 40 Cups Gypsum
⅓ to 1 Cup Bokashi 20 to 25 Cups Bokashi
½ to 1 Cup Alfalfa Meal 30 to 40 Cups Alfalfa Meal

Grower Tip: Pay attention to the plants you had in the soil prior to needing to re-amend. They will clue you in to which nutrients are missing in your soil and what needs to be added.

Vegetable & Herb Specifics:

While the above quantities will work just fine for your vegetable garden, you may find you need to use less than the recommended amounts. This is because vegetables are much less nutrient-demanding than some other crops, like cannabis. Additionally, if you find yourself low on calcium, we highly recommend adding the full amount of gypsum to your soil.

Cannabis Specifics:

The above inputs can be followed exactly for cannabis growers, whether you are growing in pots or in raised beds. Please remember to pay attention to the plants you were growing in the soil previously. This will be key in determining if other amendments need to be added to your soil during the re-amendment process.

Mixing Everything Together

Yup, you guessed it! Once all of the desired amendments are added to your soil, simply grab a shovel or rake to mix everything together.

If your soil is dumped onto a tarp, this should be fairly simple. However, if you are re-amending a bed or plot, remember not to over-till the area. It is important for us to stress that you try to only till within the top six inches of the soil – and never dig below twelve inches – to avoid disturbing the ecosystem just below your feet.

Finally, you want to let the soil “cook” for a few weeks prior to planting. This will ensure the nutrients begin to break down and integrate into the soil, making them available to be absorbed by the plants.

And that’s it…Congratulations! Your soil is officially chock-full of nutrients, and ready to grow vibrant plant babies once again!

List of organic gardening soil amendments:

This is a leguminous plant used for fodder, pasture and cover crop. It comes in crushed or pellet form. Purchase alfalfa meal or pellets at animal feed stores. Some garden nurseries may sell it as well.

  • Adds nitrogen, potassium, some phosphorus to your soil.
  • Use in your compost pile or as a mulch.

This can be purchased in garden centers, shredded in your own garden, or often given away by local tree trimming businesses.

Use finely chipped bark because it covers the soil better not allowing weeds to grow. Try to use hard wood bark if you can get it.

Cedar is best not used in your garden beds as it has oils in it that are not good for your plants. Instead use cedar chips or bark on our pathways to suppress weed growth.

  • Adds organic matter to your soil.
  • Use as a mulch. Shredded is best for blocking out weeds.

This can be purchased at garden centers or at animal feed stores.

  • Adds nitrogen.
  • Use in your compost or add directly to your soil as an organic fertilizer.

This is made from crushed animal bone and can be purchased at any garden center or nursery.

  • Adds phosphorus and some nitrogen.
  • Use in your compost or add directly to your soil. Place in the hole when transplanting.

Keep your daily coffee grounds.

Check with your local coffee shop as they will often give away their coffee grounds rather than put them in the garbage.

  • Adds nitrogen, some phosphorus and potassium to your soil.
  • Put into your compost pile.

This is a compound containing calcium and/or magnesium. It can be purchased at your local garden center or nursery.

  • Adds calcium and magnesium to your soil.
  • Applied directly to the soil and used to raise pH

Add lime to your soil if you need to raise the pH level.

This can be purchased at your local garden center or nursery.

  • Adds nitrogen, phosphorus and trace elements to your soil.
  • Used as a liquid fertilizer. It is usually diluted it in water read the package for instructions.

Collect your grass clippings, make sure they are free of pesticides.

Keep your own clippings or ask neighbors for theirs. Make sure the grass has not been chemically fertilized or it cannot be used as an organic gardening soil amendment.

  • Adds nitrogen to the soil.
  • Use as a mulch or add to the compost pile.

Is also known as glauconite. This is an ancient seabed deposit containing some potassium and has a broad spectrum of micronutrients. This can be purchased at garden centers and nurseries.

  • Adds potassium and trace minerals.
  • Used as a fertilizer add it to the compost or directly to the soil

Straw or hay are great to add to garden beds.

Find a local farmer who grows and cuts from their own fields or can also be purchased at some garden centers or animal feed stores.

  • Adds organic matter to soil.
  • Use as a mulch or can be tilled under in the fall

Collecting your own kitchen waste (not including any meat products) is probably the easiest. Often you can pick up vegetable waste from grocery stores or local restaurants so if you are looking for more than you can produce check these out.

  • Adds nutrients and organic matter to the soil.
  • Use in your compost. Do not add meat or greasy materials to the compost.

Collect leaves, shredding them is best.

Any type of leaves will work well as an organic gardening soil amendment. I collect leaves in the fall from neighbors and areas near where I live.

I then crush them by running them over with my lawn mower or weed eater. I then place them directly on my garden beds or store them to be added to my compost over the winter. Brassicas grow well in beds where composted leaves are added.

  • Adds nutrients and organic matter to the soil.
  • Use as mulch and in your compost. Shred before using.

Animal waste can be purchased at garden centers and nurseries by the bag. It is best to find a local organic animal farmer who is willing to give away or sell his animal waste.

Any animal manure is great to use except for dog or cat feces. Check out what manure is best for your garden.

  • Adds nitrogen and mineral content to your soil.
  • Used as a soil conditioner and fertilizer. Make sure it is aged for 6 months or more before using directly on your garden.

This is partially decomposed plant life taken from bogs and used as a rooting medium or soil conditioner. This organic gardening soil amendment can be purchased at garden centers and nurseries.

  • Adds organic matter to the soil and helps soil retain moisture.
  • Put it directly on the soil and till under.

This is finely ground, natural rock powder. It is one of the three major plant nutrients. It is designated by the letter P.

  • Adds phosphorus and minerals.
  • Use as a fertilizer in your compost or add directly to the soil.

This is crushed rock and another one of the three major plant nutrients. It is designated by the letter K.

  • Adds potassium.
  • Use as a fertilizer in your compost or add directly to the soil.

This is the waste left from cutting wood. It is best to use any sawdust except for cedar in your garden beds. Cedar sawdust has oils that are not good for your veggies, so use it only in your pathways. This can be purchased at garden centers or at sawmills if you have any in your area.

  • Adds organic matter to your soil.
  • Use as a mulch great for pathways.

This is a sea plant that is washed up on beaches usually after big storms. It is most available in the fall and winter months and is a great organic gardening soil amendment.

  • Adds potassium, some nitrogen, phosphorus and trace elements.
  • Use fresh seaweed in your compost pile. It can also be purchased in a dry concentrate which can be diluted in water and used as a fertilizer tea.

  • Adds a variety of nutrients.
  • Use in the compost pile.

These will add green matter to your compost pile. Make sure you only use weeds that have not gone to seed and have no disease. Destroy others so they do not contaminate your compost.

  • Adds varying nutrient content and trace minerals.
  • Add to the compost pile.

This is the grayish powder left after wood has been burned. After cleaning out your wood stove or wood burning fireplace place the ash on your garden beds or in the compost.

  • Adds nutrient content and trace elements.
  • Use in the compost pile or add directly to your soil.

This is bark, just in larger pieces. Check with your local tree trimming companies to see if they are giving it away or it can be purchased at local garden centers and nurseries.

  • Adds organic matter to your soil.
  • Use as a mulch in pathways. If adding to your garden beds you will need to add plenty of nitrogen to your soil first.

Adding organic gardening soil amendments is an important step to creating a healthy garden soil. Check out my 6 steps to a vegetable garden.

I offer online coaching for the beginner gardening wanting some guidance. I offer sessions on Skype, Zoom or by Telephone. Click here for more info .

Organic Soil Amendments

You can improve your soil with a host of Florida-friendly organic amendments, such as compost, manure, or even worm castings. By doing so, you’ll increase the nutrient content of the soil, help soil retain moisture, and also stabilize soil pH. Soil amendments are especially helpful for flower beds and vegetable gardens, since these plants need plenty of nutrients and moisture to perform well.

Organic amendments should be added before you plant an area. First loosen compacted soil with a pitchfork or tiller, then incorporate composted yard waste or composted animal manure into the soil.

Learn more about the types of organic soil amendments and how to incorporate them into your landscape in "Organic Soil Amendments."

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