Soil, Part 1: Texture

Let's start with Texture

One soil characteristic that will change very slowly and never be radically altered is your soil’s texture. Texture is determined mostly by the size of the soil particles.  Sand particles are large, so sandy soil has a light, loose texture whereas clay particles are very small, so clay soil is comparatively heavy and tight. Intermediate-size particles, such as silt or bits of organic matter, modify extremes in these two soil types.

The Scoop on Sand

Very sandy soil drains fast, which is generally a good thing! At the same time, fast drainage means that dissolved nutrients may drain away before plant roots have a chance to absorb them.  Sand particles are also slippery, so nutrients don’t bind to them. Because sand particles are large, the spaces between them are also quite roomy. For this reason, sandy soil does not need to be cultivated often since it’s air-holding capacity is already excellent.  It does need to be continually enriched with organic matter, which will enhance its ability to hold onto nutrients from fertilizer. If you garden in sand, heavy mulching is should become your best friend (and a fundamental method in your soil care practices).

Working with Clay

Tiny clay particles pack so tightly that they trap water and stay wet, so plant roots may find it difficult to push their way through the soil, and then be dissatisfied with constant wetness.  On the plus side, clay soils hold nutrients well, so rich forms of organic matter added to a clay soil may nurture plants for a long time. Clay soil responds well to cultivation -- which introduces much-needed air -- as long as you dig or till it only when it is lightly moist to dry.  If you add in compost or other soil amendments each time you replant in clay soil, over time you will see a steady lightening of your soils texture.

Acidic or Alkaline Soil (AKA Sweet & Sour)

In some regions, the chemical composition of the soil makes the water in the spaces between the particles acidic - think vinegar or lemon juice.  In other regions, the soil is alkaline, aka sweet or basic.

What’s a pH and why is it important?

The measure of the acidity or alkalinity of your soil is called the pH.  Distilled water, with a pH of 7, is neutral. Acidic soils have a pH less than 7, while alkaline soils are above 7.  Soil pH is important because it determines what nutrients are available to plants. Some nutrients are tied up in unavailable forms at certain pH levels, while others may be overabundant to the point of toxicity.  

Most plants thrive in soil with a pH between 6 and 7.5.  Some plants, such as blueberries require more acidic soil. An inexpensive pH test kit will give you a general idea of your soil’s pH, but a soil test (a handful-size sample sent to your local ag extension office) is more precise and reliable.  If your soil is acidic you can nudge it toward neutral by mixing in lime (ground up, powdered or pelletized limestone). Adding limestone doesn’t give instant results so it’s important to mix it in and allow rain to move it through soil crevices before planting seeds or plants.  Alkaline soils are harder to modify, and the first step is to add sphagnum peat, elemental sulfur, aluminum sulfate, iron sulfate, acidifying nitrogen, and organic mulches.

Whether your soil is acidic or alkaline, sandy or clay, adding organic matter via organic fertilizers and soil amendments regularly will help you achieve amazing soil results season after season.