What Are Loamy Soils?

By definition, loamy soils are friable, possessing a mixture of clay, sand, and humus (and/or silt) that is ideal for growing plants. While those new to gardening and landscaping are probably familiar with terms such as clay and sand, they might be unfamiliar with the term humus, so let's gain a better understanding of the meaning of that word before proceeding.

Humus is organic matter partly or wholly decomposed. When the decomposition is hastened by human intervention in order to use it as a soil amendment, it is virtually synonymous with compost. A generous addition of humus or compost will help make soil more friable.

What's the Big Deal About Loam?

Why are gardeners and landscapers so in love with loam? The answer is easy to understand if you consider the alternatives. For example, a soil with too much sand is too porous; water runs through it as if running through a sieve. What is the result of this porosity? Water percolates right past the plant's root systems and does not hang around long enough for them to drink it up.

On the other hand, soil with too much clay does not drain well. So you have the opposite problem: Excess water hangs around too long and rots the roots of your plants. Another problem with overly clay soils is often compaction, one solution to which is working in some loam. 

The Problem of Compacted Soil

Compacted soil is a big enough and common enough problem to warrant a closer look. Compacted is a term applied to soil which, deprived of proper aeration (perhaps due to heavy foot traffic, among other factors), suffers from excessive water runoff and poor conditions for plants to develop roots.

How do you solve the problem of compacted soil? In a lawn, you can correct the problem mechanically through core aeration. When creating a new garden bed, some people use  garden tillers to break up compacted soil in conjunction with introducing loam and other organic soil amendments. The tunneling systems created by a healthy earthworm population can help correct compacted soil conditions.

Another use for the word compaction in a horticultural context is associated with making compost, where compaction occurs under anaerobic conditions. Turning a compost pile frequently is one way to avoid such compaction.

Having Loam Delivered to Your Property

People who are not lucky enough to have a property rich in loam often have to buy it, ordering it by the truckload (priced in cubic yards). But you have to be careful that the load does not contain the rhizomes of an invasive weed such as Japanese knotweed. One suspects that loam deliveries have been largely responsible for the spread of this terrible weed over the years.

Acquiring loamy soil in this manner can become quite expensive if you are attempting to cover large areas. One compromise is to grow plants in raised beds. These structures come in many shapes and sizes. A great virtue of a raised bed is that you control the quality of the soil because you fill the empty beds with loamy and fertile soil from the onset.