Soil Amendments: How They're Defined, How They're Used

Verb Form, to "Amend" the Soil Means to Improve It

Tumbler compost bins (image) are cleaner than other types. This makes them good against rats.
David Beaulieu

Soil "amendments" (noun) are elements added to the soil, such as natural fertilizer (for example, compost), peat moss, manure, or chemical fertilizer, to improve its capacity to support plant life. 

While chemical fertilizer improves soil by adding nutrients only, soil amendments such as peat moss improve soil by making its texture or drainage more conducive to plant health. Peat moss adds no nutrients to soil.

Meanwhile, compost enhances the ground in which you plant both through adding nutrients and through improving texture and drainage. Compost, peat moss, and landscape mulch all help your soil to retain water better.

Soil amendments can also change soil pH. For example, peat moss is acidic, which makes it suitable for use around acid-loving plants.

For Pete's Sake, What Exactly Is Peat Moss?

Now that we have defined what amending the soil is, let's take a closer look at some of these individual soil amendments (and how they are used), beginning with peat moss.

The moss in the name, "peat moss" refers to a type of moss known as sphagnum moss. Sphagnum moss is a spongy material that was also traditionally used to chink log cabins. I, myself used it in building my log cabin during the youthful, back-to-the-land period of my life. This spongy character gives you a clue as to one of the virtues of peat moss as a soil amendment: it retains water well, yet it does not become compacted.

Amend your soil with peat moss to achieve "Goldilocks" drainage: not too dry, not too wet.

This soil amendment is harvested, or "mined" from peat bogs (Canada is a major producer). A bog is a type of wetland. In fact, if you are familiar with water gardens, you may know that there is a whole class of water-garden plants known as "bog" plants.

The sphagnum moss decomposed in these peat bogs over very long periods of time, meaning that, for practical purposes, peat moss is not a renewable resource. This is one reason why some people are against the continued use of peat moss.

But used it is in the green industry-- and widely. Peat moss is one of the typical ingredients used in potting soil, along with compost and, to improve drainage, perlite.

The "Black Gold" of Soil Amendments: Compost

If you will be starting a new garden from scratch for the first time in your life, one of your first steps should be to learn how to make compost. And one of the first tasks in making compost is usually to set up some type of compost bin (picture). There are many kinds of bins. The one in my photo is the type with cylinders that you can spin around, so that you do not have to turn the contents with a pitchfork (that is, the old-fashioned way). Another advantage of this so-called "tumbler" style is that it is cleaner -- an important consideration for those worried about keeping rats out of their compost bins

Composting is not just for table scraps, the leaves that you rake up in autumn, etc. You can also compost manure (from cows, horses, chickens, etc.).

In fact, it is often better to use composted, or "aged" manure than the fresh product. The latter is sometimes so hot that it burns plants.

Amending the soil with compost and other forms of organic matter can be viewed as both a problem-solving activity and as part of your regular landscape maintenance:

  1. Adding soil amendments can solve the problem of, for example, an overly sandy soil that does not retain enough water, or an overly clayey soil that, on the contrary, retains too much moisture.
  2. But you should also be amending the soil right along as part of a garden's preventive care regimen, even in the absence of known problems. Most gardeners who tend compost piles distribute mature compost to at least some of their plants annually.

If you profited from this information, you may also wish to read: How Do I Find Out My Soil Type?