December 17 2014
soil

UNDERSTANDING SOIL TYPES

soilFor gardeners and property owners, there are up to five different soil types that you can utilize for lawn, garden and landscaping.  Each of the five is made up of a combination of three types of weathered rock particles: sand, silt, and clay.  The balance of how these three particles are combined defines the soil’s type—how it feels to the touch and how it retains water and nutrients. And so – how it helps plants and trees to grow.

1. Sandy soil, of all the types, has the largest particles.  It is dry and gritty to the touch and because the particles have huge spaces between them, it doesn’t retain water well.  Instead, water drains rapidly and falls straight through to the places where the roots, particularly those of seedlings, cannot reach.  The nutrients in sandy soil are not utilized by the plants because they are quickly carried away with the runoff.  The benefit of sandy soil is that it is lightweight and warms up quickly with the spring sun.  To determine how sandy the soil is that you are working with, you simply moisten it and roll it into a ball to check the predominant particle type.  If it is sandy soil, your effort to form a ball will fail and it will crumble through your fingers.

2. Silty soil has smaller particles than sandy soil, which makes it smooth to the touch.  When wet it is sort of soapy, slick, and when you roll it between your fingers there will be a coat of dirt left on your skin.  Silty soil retains water well but it doesn’t hold on to as much volume of nutrients making it just fairly fertile.  Due to its moisture-retentive quality, silty soil is cold and drains poorly.  Silty soil can also easily compact, so it is best to avoid trampling on it when working in the garden.  It can become poorly aerated, too.

3. Clay soil has the smallest particles among the three, so it offers good water storage qualities.  It is also sticky to the touch when wet and smooth when dry.  Because of the tiny size of the particles and its tendency to settle together, little air passes through its spaces.  It is also slower to drain and has a tighter hold on plant nutrients.  Thus, clay soil is rich in plant food, which is better for growth.  It takes longer to warm up in response to the sun because the water trapped within it also needs to be warmed up.  The downside to clay soil is it can be very heavy to work with, wet or dry.  In summer months, it turns hard and compact which makes it difficult to turn. To determine if you have clay, wet it and try rolling it up into a ball.  If it forms a ball or sausage-like shape, then you have clay.

4. Peaty soil is dark brown or black in color, soft, easily compressed due to its high water content, and rich in organic matter.  When peat is drained it turns into a good growing medium.  In the summer sun and heat, peat can become very dry and create a fire hazard.  The best benefits of peat soil are its ability to hold water during the dry months and protect the roots from damage during the very wet months.  It is also helpful to regulate the soil chemistry or pH levels as well as acting like an agent of disease control for the soil.  You can tell if you have peat in your hands by wetting it and trying to form a ball.  It won’t take shape, as it is a spongy material and when squeezed, water will be released.

5. Saline soil is usually found in extremely dry regions and is usually briny because of its high salt content.  It can cause damage by stalling plant growth and germination.  It can cause problems with irrigation too.  The salty content is due to the collection of soluble salts in the rhizosphere* – high salt contents prevent water uptake by plants, leading to drought and stress to the plant.  As with the other soils, it is easy to find if you have saline soil.  You will probably see a white layer coating on the surface, your plants aren’t doing well, and you will see leaf tip burn on the younger leaves.

Loam is the ideal soil type for gardening.  It contains a balance of sand, silt and clay that creates higher pH and calcium levels due to its previous organic matter content. The key characteristics of loam are its dark color and mealy texture, which is soft, dry and crumbly.  It holds nutrients well and yet drains well.  The touch test for loam is a smooth, partly gritty, partly sticky ball that crumbles easily.  Although loamy soil is the ideal material to work with, don’t despair if you don’t have it in our garden.  You can condition your soil by adding beneficial soil inoculents, cover your soil with compost or simply spray the area with compost tea. Don’t hesitate to ask your landscaping and gardening professional here at our center about how to improve your soil and growing power!

*The rhizosphere is a certain section of the soil in the ground and will be the subject of an upcoming article.