Soil:
The Basis for a
Healthy Garden
Winter - 2004
By Suzzanna Walsh, Master Gardener
Soil Types
Ah, life is a beach, at least here on the
Your garden soil needs to provide your plants with the fundamentals needed for
life: oxygen, nutrients, and water. The
better your soil is at providing these fundamentals, the better your garden
will grow, and you will spend less time and effort working there. A
Soil texture refers to relative proportions of sand, silt, and clay within your
soil. Soil texture determines tilth
(fitness as a medium for growing plants) in addition to nutrient and water
holding capacity. This is paramount to
healthy plant growth. There are 12
recognized soil textural classes that can be lumped into 3 general categories:
coarse texture (sandy soil); medium texture (loamy soil); and fine texture
(clay soils). The coarser the soil
texture, the faster the soil warms in spring.
Soils with finer textures hold water and nutrients better than coarse
textures.
Clay soils retain more water and nutrients than sand, but there is little
percolation of the water and less oxygen for the plant due to smaller pore
sizes than those of coarser textures.
Finally, loam, what gardeners dream about as the vernal equinox draws near, is
the ideal soil, holding water, nutrients, and oxygen in a balance of sand, clay
and organic matter.
What type of soil do you have?
Identification of soil is discussed below.
Soil Identification
What type of soil do you have? Or, more
accurately, what is your soil texture?
In part one I wrote that soil texture is the relative proportion of
sand, silt, and clay within your soil.
Soil texture determines it’s fitness as a medium for growing healthy
plants, and includes nutrient and water holding capacity.
Soil texture can be determined by what is called the ‘feel’ method. This sounds easier than it proves to be. This method takes some experience, so get out
there and give it a try. Start with
moist soil. A handful will do. Remember to screen out the gravels and small
rocks before you start. Add a small
amount of water if the soil is a little dry.
Clay soil forms a hard and sticky lump when squeezed. A handful of damp sandy soil will not hold
together and will crumble. Loam (the
gardeners dream soil) will hold its shape when squeezed, and will crumble only
when squeezed hard.
Another ‘feel’ method is the ribbon method.
Start with damp soil in your hand and rub it between your thumb and
forefinger. Look to see how the soil
pushes out into a thin strip, how it hangs together, and how sticky, smooth, or
gritty it is. A clay ‘ribbon’ will be
strong and will take a lot of handling.
You should be able to make a ribbon of at least one inch.
These two methods will take some experience to ‘get a feel for’. If you’re feeling a little frustrated and,
well, muddy, try this method: get a large glass jar, add a handful of soil to
it, fill it with water, and stir well.
Let it settle for a couple of hours and then check it out. If you have sandy soil most of the sand
particles will sink, forming a layer on the bottom of the jar. The water will look pretty clear. If you have clay soil there will be a thin
layer of particles on the jar bottom but it will take them quite a while to get
there. The water will look cloudy. If you are lucky enough to have loam, the
water in the jar will look fairly clear, and there will be a thin layer of
sediment on the bottom with the smallest soil particles on top.
So get that trowel out. Get those hands
dirty. Put those empty mayonnaise jars
to use, and figure out your soil type.
The third, and final, chapter of this series will discuss how to amend
your newly identified soil so you will have the best ‘dirt’ in your neighborhood,
and I don’t mean gossip!
Soil Amendment
Thus far we/ve reviewed soil types and identification. A
garden soil in good physical condition can hold, and provide to plant roots,
adequate water, nutrients and air. Now that you’ve
learned what type of soil you have, you may proceed forward to get the
type of soil you want. Remember, soil affects
not only how well your plants thrive, but also how much time and effort your
garden requires on your part.
Sometimes our garden soil needs our help. We’ll review
the two most common problem soils for our area: those that have high percentages
of clay and, conversely, those that have high percentages of sand. If you discovered you have loam - rejoice!
Now let’s ‘dig into’ the subject at hand. Should you
have clay soil, you have the potential advantage of having soil that will hold
many nutrients, but unfortunately, may tend to have terrible drainage. Many clay soils are hard when dry, and sticky when wet. The first step to improving clay soil is to improve soil
structure to promote better drainage. Add organic
materials such as compost or aged or rotted manure which improves the structure
of heavy soils as well as enriches poor soils.
Should you have sandy soil you have the benefit of soil that is easily worked
and easily improved. Unfortunately, sandy soils may
lack nutrients, can drain too freely, and may dry out too quickly. These problems can be improved by adding organic materials
as well as fertilizers. Compost and manure amendments
improve both water and nutrient retention.
Organic materials are very effective when garden soils are amended by at least
30 percent by volume. Apply one inch of soil amendment
for every three inches of soil you wish to amend and work it in well.
For our plants to thrive they must have oxygen, water, and nutrients, and
strong, healthy soil. To have strong, healthy soil we
may need to feed it - just as we feed our bodies to achieve strength and health. With strong, healthy soil the nutrients we apply will be
available for efficient use and be less prone to loses from leaching. Applying a thick layer of mulch will help avoid reliance
on chemical weed control. Soon you’ll have the best
dirt in your neighborhood.