Soil Amendments

Some people think that fertilizers are lumped into the subject of soil amendments and some say they are different subjects. I separated Organic Fertilizers from “Amendments” just for your ease of learning. I think the more differentiation the better when everything seems confusing. But you can group it however you would like. Plus some of these things fit in both categories. 

Amendments usually have to do with drainage/water retention. Fertilizers are food.

I should add that a lot of the information you will get when studying this subject is just the opinion of someone. That means that sometimes information between two growers can conflict. That's why I want to equip you with the definitions of what things are so you can understand what each is saying and be able to form your own opinions instead of getting annoyed and confused and maybe quitting before you start.

Peat Moss vs. Sphagnum moss

Words you will run into regarding this are as follows:

Peat Moss looks like dirt with clumps of some stringy root looking material and remnants of bark and other unidentifiable clumps. If you look it up most references will tell you it is simply Sphagnum moss. And some will go on to say how you shouldn't use it because it is not sustainable and takes 1000 years to make. Well if it is just a moss, why does it take 1000 years to make? 

Here's what I found. Sphagnum moss is a green moss when it is sold alive. It can be used to decorate baskets, terrariums and other decorative things.

It is tawny colored when it is dead and dried, much lighter in color than peat moss. It can be used as a soil additive and/or mulch on its own and is good when growing seeds because it protects and retains moisture, and it is not acidic like peat moss. It is not commonly used. If you ask for it, you are likely to get Peat Moss. Peat moss is not an actual moss like Sphagnum is.

Sphagnum moss is a component of Peat Moss. Peat Moss gets made from plant remnants that sink to the bottom of cold wetlands of which Sphagnum is a large component. Then on the cold bottom it decays, but the decay is slow because there is no oxygen to support any microbes. Layers and layers of this pile up over the centuries and that's why it takes 1000 years to make Peat Moss.

More on Peat Moss

But Peat Moss is very versatile. And it is very light to ship. It became extremely popular in the 1950’s as a soil amendment because if you mix it with a clay soil it aerates it and increases water drainage, but if you use it in a sandy soil it binds it and helps with water retention. And in silt it adds needed nutrients and keeps it from compressing. 

Peat Moss is also used to remedy the pH of soil if it is too alkaline or adjust soil to plants that like acid. It itself is acidic. Some plants that like peat moss are strawberries, blueberries, herbs like mint, oregano, basil, rosemary, thyme, lettuce, leeks and asparagus and flowering plants like azaleas, hydrangeas (Snowballs) and camellias.

Some say Peat Moss is considered very sterile because no microbes formed it so it can protect plants from diseases. 

It is a popular mulch in the north but in hotter climates it could be problematic. The problem is that although it holds 25 - 75% of its weight in water, on top of the soil on very hot days it can still get all dried out and when that happens it turns hard and repels water and it is hard to get it wet again. 

Prepare Your Garden for Success

Some things that can be used instead of Peat Moss are defined below.

Top Soil is just plain soil that you find on the earth's surface up to 12 inches down. Basic soil is made of the basic soil ingredients of sand, silt and clay. It is heavier than garden soil or potting mix or planting mix and is much less expensive. When you want to bring in soil to a construction site it is usually top soil that is trucked in. Top soil is used in landscaping and gardening. It, depending on its mixture, can be used to improve existing soil.

Garden Soil, Potting Mix or Planting soil is the above mixed with more organic material and soil amendments which tailor it to the plants it is going to have growing in it.

Lime makes the soil alkaline. It is added to the soil as crushed limestone. Its main components are calcium and magnesium carbonate. Some plants that like limestone are asparagus and cabbage as well as many decorative flowering plants like Lilacs and Lavender. Hydrangea in alkaline soil will make red or pink flowers instead of the blue they make in acidic soil. In neutral soil it can make purple or a combination of blue and pink. Lime and peat moss can be used to adjust the pH of the soil up or down.

Regulating Your Soil’s Moisture

Gypsum is calcium sulfate with 2 water molecules attached. It is a fascinating substance. Depending on how many waters are attached to its basic structure it makes totally different substances from alabaster and selenite to plaster of Paris!  

It is mined and when put in garden soil it provides calcium and sulfur which can increase the growth of many plants such as grapes, peanuts, potatoes, alfalfa, strawberries, corn, wheat, watermelon, citrus and other fruit trees. Also many landscape plants and beautiful showy flowers.

Gypsum is also used to treat blossom end rot in tomatoes and peppers which is caused by calcium deficiency.

Gypsum is a way to add calcium without changing the pH. It keeps the surface dirt from caking so new seed plants can break through the surface sooner and it makes water more able to penetrate the soil.

Coconut Coir is a fiber gotten from the outer surface of coconut shells.When added to soil it breaks down clumps and loosens up clay so it can drain. On looser soils it binds and helps with water retention. Its drawbacks are cost, high salt content, dustiness and it might harbor weed seeds.

Perlite - Volcanic glass like rock that is mined and then super heated till it pops, kind of like popcorn. It looks like little squishy white balls. They are added to soil for water retention and to aerate the soil. 

When I was a kid there were two sizes: the large was called perlite and the small was called vermiculite. Either this has changed or someone was mistaken. 

Cactus or succulent mixes usually contain perlite. Perlite provides water, but also keeps the soil dry preventing root rot.

Other Amendments

Vermiculite - Volcanic mica-like mineral also subjected to the popping process, but this makes a sort of accordion shape that absorbs some water, but not as much as perlite. It is used to make the soil looser and more aerated. Vermiculite is a light brown powder that looks like it has shiny mica looking particles sprinkled in it.

Although it doesn't retain as much water as perlite it keeps the soil wetter longer. It doesn't hold the water away from the soil like perlite does.

Water loving plants like ferns, spider plants, and even certain herbs, like basil or parsley do well with vermiculite.

Pumice is a porous volcanic stone. It does not require industrial processes. It is harder and heavier than perlite, but it is also more expensive and not as easily available. It makes for a more stable pot which is better for tall plants and although it behaves pretty much the same as perlite it doesn't decompose and it doesn't gradually rise to the top of the soil needing redistribution after a while like perlite does. It stays put.

LECA - Stands for Lightweight Expanded Clay Aggregate. It is basically porous clay balls. It was developed as a semi hydroponic medium but can be used at the bottom of a soil filled pot or container to retain water instead of stones. It is rather expensive but can be helpful to people who can't figure out how much to water their plants. The balls contact water from a dish under the pot and provide a steady water supply so the roots can drink whenever they want without risking root rot.

New Sustainable Solutions for Healthy Soil

Rice Hulls are a more recent material used to improve aeration and water retention. They weren't available before the invention of modern rice hullers. Rice hulls contain silica, lignin and other nutrients so as a natural material it should become more and more available and popular. This is something that acts as a fertilizer as well as a soil amendment.

Biochar - relatively new. This is basically charcoal made without oxygen being present which means very high temperatures were used. In the presence of oxygen flames would be prohibitive. This soil amendment is alkaline. 

It does pretty much the same thing as coconut coir or perlite but it can trap nutrients away from the plant as well. It can be soaked in nutrients ahead of time and then will provide a slow release of nutrients.

Also it provides a haven for microbes which is a very good plus point in the soil.

This additive is an attempt to not just burn up fossil fuel but to reduce the waste back to charcoal and return it to the soil instead, reducing greenhouse gases.

I hope this information clarifies what can be used to tailor your soil to what you want to grow and will allow you to converse intelligently and read up on things you want to grow without feeling overwhelmed. 

*This article is intended for informational purposes. The statements above have not been evaluated by the Food and Drug Administration (FDA). This product is not intended to diagnose, treat, cure or prevent any disease.