Gardening 101: Soil Amendments

In the last Gardening 101 post, you learned about the different types of soil [clay, sand, silt, and loam], along with the pro’s and con’s of each. I also mentioned that in today’s post I would share with you what you can add to your soil to improve its ability to support and sustain plant life.

There are two categories of soil amendments – organic and inorganic. I’m going to focus on the soil additives I believe are most common and frequently used by gardeners.

(When solutions are given for clay soil, they can also be applied to silty soil.)

Organic Soil Amendments


What is compost? I found a good definition on University of Illinois extension, Composting in The Home Garden. “Compost is decomposed organic material. Compost is made with material such as leaves, shredded twigs, and kitchen scraps from plants… The composting process involves four main components: organic matter, moisture, oxygen, and bacteria.”

In a future post, I’ll walk you through how to make your own compost. One type of compost is cow manure, which is the next topic.

Cow Manure

Yip, that’s right – cow pooh-pooh. If you’ve gardened for any length of time, this is probably old news. If, however, you’re new to gardening, then the idea of adding cow manure to your plant soil may seem a bit… archaic, rudimentary, antiquated, and just plain GROSS!! But take heart. The experience of working with cow manure is not at all what you’ve probably conjured up in your mind.

It’s not an unpleasant experience for a couple reasons. The cow manure you purchase (in bags at your local garden store) is usually mixed in with other composted matter, and, more importantly, it’s been “aged”. Fresh cow manure will burn a plant because of the unusable (in its current state) and high levels of nitrogen. So you should never use it unless it has aged at least 6 months. (And by that time, there’s no smell at all.)

“Fresh manure (and any fresh organic matter such as fruit rinds or eggshells) contain a lot of plant nutrients but they are bound up in the organic matter and therefore unusable by a plant until the organic matter is composted or rotted, releasing the bound up nutrients. This is the process by which bacteria break down the organic matter releasing the bound-up nutrients.” [Source: Hydroponics At Home]

It’s important to mention that not all animal manure should be used in gardening. Just because you live on a farm or have domesticated pets, doesn’t mean you have your own little factory and assembly line of plant-fertilizer-producing creatures. Horse, cow, and chicken manure are good to use in gardens. Dog, cat, and pig manure are not good for gardens, especially vegetable gardens. “They can carry disease organisms and parasites that can be transmitted to humans.” [Source: Farmer Fred]

Farmer Fred gives another important benefit of manure:

“The most important benefit of manure is as a soil conditioner. Mixing manure into a sandy soil is like introducing thousands of tiny sponges that help retain moisture. Manure also helps loosen and aerify a compacted clay soil.

Manures also transport useful microbial hitchhikers. These living components of organic matter manufacture glues that cement soil particles into crumbs. Crumbly soil is ideal as far as most plants are concerned because its structure allows it to hold both air and water.”

So, as you’ve just learned, manure is excellent for sandy and clay soil. Be sure to check out the rest of what Farmer Fred has to say on the subject of manure.

Peat Moss

“Peat Moss is the decomposing, dead parts of sphagnum moss that usually are found deep in a bog. It is rich in organic matter, and typically can hold up to 20 times its weight in water. For this reason, peat moss mulch can be used in dry areas to help retain water. It also is acidic and can be used to lower the pH in soil.” [Source: Wise Geek]

Peat Moss consistency is somewhere between sawdust and fine mulch.

Sphagnum Peat Moss (2.2 cu ft ~$8.48)

Sphagnum Peat Moss


Since it can hold up to 20 times its weight in water, it helps keep soil from drying out during hotter, dryer times of the year. If you have sandy soil (which does not hold water), this will help your soil retain needed moisture.

Inorganic Soil Amendments


I think you all know what sand is. Sand is good to add to clay soil to help loosen it up. I recently learned that not just any ‘ole sand will do though. Apparently, you should NEVER mix play sand with clay. It will make a bad situation worse, like concrete… the opposite of what you’re trying to accomplish. You want to use coarse sand. Play sand is very fine. [Source: iVillage Garden Web]


You’ve probably seen Perlite and didn’t know that’s what you were looking at. Perlite is a mineral, a by-product of volcanic activity. It’s white in color and super light. It makes me think of bee-bee pellet-sized Styrofoam.

Perlite (20 lbs. ~$14.70)



This is also good to add to clay soil because it provides aeration, drainage, and allows better root growth.


It’s less likely that you’ve seen Vermiculite. Like Perlite, it’s a mineral, but it has a shiny appearance.

Vermiculite is good to add to sandy soil because it helps hold water.


Since both Perlite and Vermiculite are minerals, they’re probably a good nutrient source for plants, in addition to the benefits already mentioned.

I hope this was helpful.  :)

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