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The Definitive Guide to Soil Amendments – A Complete List

When you first get into gardening you think it will be as easy as planting a plant, and harvesting a huge bounty of food. Then you realize that soil quality plays a huge role in what your plants and garden will turn out to be.

Anyone that has gardened for any length of time will inevitably run into issues related to soil health. If you are growing tomatoes, blossom end rot is a typical issue you may run into. Most people don't realize that blossom end rot is from lack of calcium in the soil. Once you figure this out you then start your soil balancing quest.

Keeping your soil “healthy” is a multi-faceted issue. It's not just nutrients that make a soil healthy, it is organic matter, drainage, aeration, etc.. This can be overwhelming to most people when they first learn what it may take to have a healthy soil. It shouldn't be though. With a simple soil test, you can take most of the guess work out of balancing your soils nutrients.

Local extension offices usually offer free or reduced cost soil tests. Depending on the size of your garden or yard, you may want to adjust how you take your soil samples, and where you take your soil samples. For a small backyard garden taking a single sample makes sense. No need to spend the money on 10 samples for a 10' x 10' garden.

If you are sampling your entire yard, or a larger garden or farm, then more samples should be considered. Taking different samples from different areas needs to be purposeful. If you have a depression in your yard or garden, that should be it's own sample. If part of your yard or garden is shaded heavily by trees that may need to be it's own sample. If you notice different rates of growth in different areas, then multiple samples to show you the difference in nutrient make up of the soil would be a good idea.

Once you have your sample send them in, and wait for the results. Something to keep in mind is that pretty much 10 different labs will give you 10 different results. They should be close, but they seem to never be exactly the same. It's best to pick a well known lab for the best results.

You may choose to get a basic soil test with NPK and organic matter. This would be fine for a lawn, but may lack valuable information for a garden or farm. The more information you receive from the lab the better informed you can be when picking the right soil amendments to balance your soil.

You can opt to receive a soil balancing suggestion from the soil lab for a few extra dollars. For most people this will be money well spent. For the few that know how and what to apply you can skip this step.

Once you get your results in, with suggestions, you will then need to plot out what soil amendments you will use to adjust any issue you may be seeing in your soil.

Macro-nutrients, or the big guys n-p-k, etc.. are not the only nutrients you will need to pay attention to when balancing your soil. Micro-nutrients can play just as big of a roll in plant health even though there only needs to be a minuscule amount in the soil. Again, if you get a soil test that covers everything, it will make it easier for your garden to thrive.

We have compiled this ultimate list of soil amendments to help you in choosing what amendments you can use to help balance out your soil, and increase the health of your plants. This list will cover most well known soil amendments as well as some lesser known amendments that you may not be aware of.

This is the definitive guide to soil amendments 

Alfalfa Meal - is a natural source of readily available nitrogen for plants. It can be used in compost teas as a microbe catalyst to improve the growth of microbes in your teas. This amendment can be spread on soil, or made into a tea and watered in.


Aragonite - Aragonite is a sea calcium that is exceptionally high in calcium and low in magnesium. It is made from mollusk shells, and can be used on soils that need calcium, but no magnesium. This is a great soil amendment to use on soils that have had dolomite lime added to it for many years. The aragonite can help to balance back out the soil nutrients so that there are no problems with tied up nutrients.

Azomite - AZOMITE is a natural mineral substance which is mined directly from its Utah desert source. OMRI-Listed for organic production, AZOMITE can be used as an agricultural fertilizer and/or soil amendment product, It is easy and safe to use and good for the environment. It contains over 60 minerals that are good for plant growth.

Basalt Rock Dust – Basalt is a naturally mined mineral that contains trace elements. Silica is an important nutrient needed for plant growth, and basalt is a great choice for that.

Bat Guano – Bat guano comes in many different NPK values. You can get guano's high in nitrogen, or guano's high in phosphorous. They are more readily available with their nutrients than most other amendments, and most of the nutrients contained in them will be used up within 3 to 4 weeks. They are a good choice fro a quick boost, and can be added to teas. Keep in mind that the harvesting of bat guano may kill the bats environment which can displace, or even kill the bats in some cases.

Bentonite Clay – Bentonite clay is an all natural way to retain moisture in your soil. It can be used as an alternative to the chemical based gel beads you see in commercial potting soils.

Biochar – Biochar is a specialty product that is similar to charcoal. Because of its precise manufacturing procedures it will survive for thousands of years in the soil. It is known to be a habitat for microbes, and larger pieces can aid in soil aeration helping to resist compaction long term.

Biosolids (treated sewage sludge) – This use to be a widely used amendment, but not in many years. For obvious reasons stay away from it.

Blood Meal - is a byproduct that is extremely high in readily available nitrogen. A little goes a long way, and if you apply to much you can easily burn your plants.

Bone Char - is a burned bone product that is like charcoal that provides phosphorus to the soil

Bone Meal  - is another byproduct that contains high levels of phosphorous and also provides calcium. It to can burn your plants so caution should be taken when applying large amount to your soil.

Calphos (Colloidal Phosphate) - Calphos is a natural, untreated soft phosphate with colloidal clay containing valuable minor minerals in addition to phosphorus. It is not acid forming, will not cake or harden and spreads easily through any type of lime, phosphate or fertilizer spreader. This is a great choice to use for replenishment of calcium and phosphorous.

Comfrey - Comfrey has the three major nutrients Nitrogen, Phosphorous, and potassium plus high levels of calcium, which can be very beneficial if harvested and made into comfrey tea for plants. Making the tea can be as easy as soaking the leaves, or you can bubble like a compost tea. Fully fermenting the comfrey may preserve its nutrients that can be used season long.

Compost – Adding compost is the tried and true organic way to increase soil health. It can help retain moisture in soils, can help to loosen clay soils, and also add much needed microbial life to all soils. If you are using compost bought from a store, it is always a best practice to mix and match the types of compost you apply. This will ensure you have a diverse coalition of microbes in your soil. Compost can be applied to the soil directly, or made into a compost tea and sprayed or watered on. Stay away from municipal yard waste compost. It s can contain chemical residue from products used on lawns like Roundup.

Corn Gluten Meal - Can aid in the prevention of weed growth when used as a per-emergent on lawns early in the season.

Cottonseed Hulls – This byproduct of the cotton industry can be used to aerate clay soils, and bring organic matter in. Often used as a mulch product.

Cottonseed Meal – Good choice for a slow release nitrogen amendment that will also lower soil ph. Good choice for acid loving plants like blueberries.

Crushed Oyster Shells – Crushed oyster shells can aid in aeration of soils, and also bring a very long term slow release calcium source.

Crustacean Meal – Crustacean Meal is a blend of different meals. It may contain crab, shrimp, or lobster meals. It can act as along term nitrogen source, and help with microbial activity in the soil.

Diatomaceous Earth - Diatomaceous earth made form fossilized skeletal remains of diatoms which are minuscule aquatic organisms. It is a great source of silica for your plants.

Dolomite Limestone - raises pH in acidic soils and is a quality source of calcium and magnesium.

Dried Molasses – Dried Molasses is usually a molasses type product that is sprayed on to a carrier. It is very reasonably priced, and is great for spreading on lawns and gardens to increase microbial activity.

Feather Meal – Feather meal is a byproduct of the poultry industry. It is cooked and sterilized under extreme heat using steam pressure cookers. It is a solid source of nitrogen that will release slowly over time. It is best to source an organic feather meal so that your meal doesn't contain trace amounts of arsenic which is used in non-organic poultry feed.

Fish Bone Meal – Fish bone meal is a super high phosphorous amendment that is a waste product from the fishing industry. It is a better alternative to standard bone meal as it will not come from farm animals that are injected with antibiotics and hormones.

Fish Meal - is an excellent source of nitrogen and is a byproduct of the fish industry. Most fish meal in America comes form the catfish industry in the Southern US.

Forest Waste – AKA wood chips, work great at bringing in organic matter for your soil to digest. It will also help to bring a fungal component to your soil. Be careful not to add to much as it can draw nitrogen form the soil and rob your plants.

Granite Meal - is a rock powder that provides a roughly 5% slow release potassium and trace minerals without changing the pH of your soil.

Greensand - fertilizer is a rich source of glauconite, which is high in iron, potassium and magnesium. It also helps loosen soil, improve moisture retention, soften hard water, and increase root growth.

Gypsum - other wise known as (calcium sulfate)gets deep in the soil layers very quickly and provides the needed calcium and sulfur.  It will also improve the soil structure and drainage or if you want to eliminate the toxic effect of aluminum. Its calcium component does not alter the PH of the soil, and it is, therefore, the best for soils with high PH level but with calcium deficiency.

High Calcium Lime - raises the pH of the soil to increase the release of phosphorous and potassium from their insoluble compounds, making them plant available.

Horsetail Grass - is rich in silicon and helps plants to resist fungal diseases via increasing their light absorbing capabilities. It can be brewed into a tea, or fermented in to an extract.

Humic Acid – Humic acid is mined from ancient remains of decomposed organic plant materials. It can help to retain moisture in the soil and aid microbial life.

Humus – is the organic component of soil, formed by the decomposition of leaves and other plant material by soil microorganisms. Humus can help to retain moisture in soils, aerate soils, and add much needed life to soils.

Hydrated Lime – Hydrated lime can be used to raise the soils PH, and may improve soil health via Ph adjustment. This form of lime is more readily available than others.

Kelp Meal - is a dried seaweed product. There are different sources from a round the world that tout different micro-nutrients and amino acids. Its enzymes can  stimulate plant and root growth. It is known to contain a plant growth hormone that made aid plants in growing more robust. Kelp meal can be used in compost teas as an additive to feed microbes.

Limestone – Limestone is a natural mineral that helps neutralize soil acidity, improves soil structure, and increases the availability of elements in soil.

Magnesium Sulfate – AKA as Epsom Salts is a fast acting source of magnesium and sulfur. It can be hand broadcast on lawns, or made into a liquid and sprayed.

Manure – Manure has been added to field crops for thousands of years. For safeties sake, use aged manure as fresh manure can burn plants.

Neem Seed Meal – Neem seed meal is a waste product of the neem industry. It is high in nitrogen, and is known to help battle pest issues in soil.

Nettles – Using nettles in a tea can help to boost a plants immunity, and ward off pests. Chlorophyll, nitrogen, iron, potassium, copper, zinc, magnesium, calcium, Vitamins A, B1, B5, C, D, E, and K, combine together to create a tonic and immune builder

Oyster Shell Flour – Oyster shell flour is an all natural ph adjuster for soils. It can provide large amounts of calcium, and is a better alternative to limestone, except for the cost.

Peanut Meal – is a high nitrogen by-product of the peanut industry. GMO and pesticide issues could be of concern unless your peanut source is certified organic.

Rice Hulls – rice hulls contain silica, and also can help to aerate your soil. They can be used as a mulch, or added into the soil for extra organic matter. You can alternatively compost the rice hulls and kill two birds with one stone by adding the benefits of rice hulls with the benefits of compost.

Sawdust – Is very high in carbon and best used as a component of a well made compost.

Seabird Guano – Seabird guano is like bat guano, but typically only comes in a high phosphorous blend. Not like the harvesting of bat guano, seabird guano doesn't usually pose any issues with the habitats of the birds.

Shrimp Meal - is ground up shrimp parts that are waste from the shrimp industry. It contains high levels of nitrogen and phosphorous, and will act as a slower release all season fertilizer.

Soybean Meal - contains a high amount of slow release nitrogen with lesser amounts of potassium. Most soybeans grown are GMO crops, so sourcing a non-gmo product is important.

Sphagnum Peat – Peat moss can be mixed into soil to add texture, and help aid in moisture retention. It is also good for raising the ph of most any soil. This can be important when growing crops like blueberries.

Straw – Straw can be used to help aerate soils, and add organic matter. It can take a long time to break down so applying in the fall is a best practice.

Sul-Po-Mag - AKA langbeinite, is good when you need magnesium and potassium but not calcium. Sul-Po-mag will not raise the soils ph.

Sulfate of Potash - contains roughly 50% potassium and 18% sulfur. It also contains trace minerals, and is mined in Ogden  Utah.

Wood Ash – can help to raise the soils alkalinity and also provide nitrogen

Worm Castings – worm casting are nothing more than worm poop. They offer similar benefits as adding compost. They are perfect for adding microbial life to the soil, and may best be used as a tea for cost reasons.

Yard Waste – Contains some nitrogen and trace amounts of potassium and phosphorus. Fresh grass clippings are nitrogen rich, but dried out grass clippings are carbon rich. Where as dried leaves are carbon rich. Grass clippings can take a while to break down so applying the season before is advised. Using yard waste as mulch is a great idea, and can cut down on weeds in your flower beds. The preferable way to use yard waste is to compost it before application.

Yarrow – Can be used as compost accelerator, or for the micro-nutrients is contains. It may best be used as a tea or fermented plant extract as supplying large amounts may be cost prohibitive.

Willow Bark – contains a growth hormone that may be beneficial to plants. Willow water has long been used to root cuttings of plants. Making a nutrient rich tea with it and applying to yards and gardens can be beneficial. If you have a good source incorporating it into the soil would add organic matter along with all of the of the other benefits.

Zeolites - are made from volcanic stones. Zeolite is capable of holding up to 60% of its weight in water. Tests have shown Zeolite can increase water infiltration by 7%-30% on gently sloped land and up to 50% on steeply sloped land, and can improve water and mineral retention in sandy soils. Zeolite amended soils show both increased water retention and nutrient utilization.

Now that you have the tools needed to balance your soil, use this complete list of soil amendments to increase the health of your garden soil. Remember that increasing soil health won't happen over night. It may take multiple years to perfectly balance the nutrients in your soil. As long as you are addressing the issues, over time your soil health will improve. This will eventually lead to healthier crops, which in turn can lead to higher yields, and plants that are resistant to disease and pests. Enjoy the soil balancing journey.

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