Advice on Garden Soils - Clay |
Sandy | Loam |
Garden soils can be silt, sandy or clay based. (There
are other types of garden soil as well, but these are a
good starting point)
great 'diarist' - John Evelyn - wrote in
1675...That in his opinion, there were no less
than 179,001,060 different types of
earth........! Time is short, so forgive me if
I only mention a few!
normally referred to as being one of three basic
'soil structure' groups; Sandy soil, Clay soil and
Loam.. This is just the start, but it is a good
starting point, for each of these groups tell us
much about the garden soil, and what - if anything
- needs to be done to improve it.
The one thing
above all I have personally found, is that encouraging a good
earthworm population in your soil will
improve all your other efforts hugely.
easiest way to find which structure group your
garden soil is in, is by testing it in an old
coffee jar - take the label off as you will need
to see through it. (I'm sure that there are many
other jars suited to this job; I happen to drink a
lot of coffee!)
This is a great way to get the kids involved -
they can even do it for you!
What You Do!
assume that you
the same in all parts of the garden, and the soil
be roughly the same sort of texture to the full
depth of a garden spade.
Take a couple of
typical (!) spoonfuls; break it up as much as you
can, then place it in the jar - just under half a
jar full is ideal. Fill the jar with water to
within a cm of the top and give it a really good
shake (Make sure that the lid is on!) Keep shaking
until all of the soil has 'dissolved' and you just
have a murky-looking liquid. Leave the jar
somewhere to let the contents settle; this will
take a few hours.
What Soil Have
now have several layers of 'soil' types in your
jar. At the bottom will be the stone/sand layer,
then a 'silt/clay layer, followed by an organic
layer. Right at the top the will be a settling of
clay. (The cloudy water is in fact a solution of
clay particles.) From largest to smallest, the
particles are... stones, sand, silt, clay. The one
we have missed (organic) can come in all sizes!
From the finest humus particles, right up to dead
sand, silt and clay elements are all mineral
(in-organic). The organic content is made up of
the 'remnants' of things that once lived. If it
lived (Animal or Vegetable), and it is now dead,
then for the purpose of this article, it is now
the 'organic' content of your soil. (There are
-should be - living things in your soil. These are
not part of your soil's organic matter! Another
section for this).
mineral bits that you can actually see
individually, are sand particles. You will need a
microscope to see the individual particles of
silt, and the smaller individual clay particles
can only be seen with an electron microscope!
Whatever your soil group, it will have all three
mineral particle sizes in it. The ratio of these
particles, determines your soil group.
a clay -
or silt - soil if you have more of those particles
in it than sandy particles. If you rub it between
finger and thumb when wet, a 'silt soil' will have
a light smooth feel, but won't shine. The finer
'clay soil' will shine and feel sticky. If the
soil feels rough to varying degrees, then you have
a sand soil. Maybe a coarse sand with larger,
rougher particles or a smooth sand, with smaller,
'test' reveals more or less equal portions of
sand, silt and clay, then you are blessed with the
ultimate (generally speaking) A 'loam soil'.
organic content of the soil is also very
important. You can also change the organic content
of the soil quite easily. You cannot change the
soil structure group very easily. If is is 'clay'
it will remain clay - unless you take some very,
very drastic measures.
improve a clay soil: You can improve a sandy soil:
But it will still remain clay or sandy!
Heavy Clay Soil in Dry
possibly the most difficult to improve, but do
have a real advantage over sandy soils - so don't
start feeling sorry for yourself just yet.
sticky when wet, and form hard lumps, which are
impossible to break down when dry. In hot weather
they form large, deep, cracks. These cracks
can rupture roots, and cause moisture loss - which
makes the problem even worse. Regular hoeing helps
to fill the cracks and forms a surface mulch,
which will help retain the soil moisture.
doubt, all clay soils can be improved quite
substantially, with the addition of
mulches of organic
matter, by way of straw stable manure, or a good
grade of peat. Composted bark - not bark chippings
- is also good. A few years of such applications
can provide you with a workable soil. Clay still -
clay soil is seriously waterlogged, then you will
need to think (do something) about land drainage.
Plants will not grow in waterlogged conditions
the advantage. Clay soils are usually rich in
plant nutrients. They also retain much of the
fertilizers that you apply. This is because the
soil moisture - which holds the nutrients to a
degree - does not soak away, taking the nutrients
with it. It may evaporate, but the nutrients stay
are usually warmer than clay soils. This makes
them better for the earlier crops of vegetables -
but not so good for the moisture-loving fruit
crops. They do not hold soil moisture. The soil
moisture usually drains away; taking much of the
nutrient away with it. These soils need
fertilizing often - but sparingly. The only way to
improve the basic moisture-loss problem, is to
incorporate substantial amounts of organic
material (which holds moisture).
Fertilizers and organic material should be
incorporated in just the top few inches of these
soils. The nutrients then take longer to leach
away. Organic fertilizers are probably best in
such soil; they don't wander off with the first
soils are usually acid (see below) and require
frequent - but small - applications of garden
the advantages of both the above soils, with none
of the disadvantages. Simple as that!
plants grow well in them, they are easy to 'work'
in most weather conditions, and they hold soil
moisture and therefore the nutrients quite well.
As with both the above soil types, Added organic
matter can only improve it more!
has to be
present in the soil for plants to grow. That's why desserts are simply
'desserts' - not sandy soils!
rich in organic matter (Humus) will both hold
moisture, and allow surplus moisture to drain
away! How? Organic matter acts as a sponge in
collecting and holding onto soil moisture, but it
also helps the soil to form a good 'crumb
structure'. That is to say, that it assists the
individual soil particles to group together into
larger groupings - or crumbs. This then allows the
soil to become more workable or friable; instead
of being one solid mass.
soil has an open structure, which allows air into
the small spaces between the individual crumbs.
Roots need oxygen. It also allows soil moisture to
percolate into these spaces. Soil moisture holds
nutrients. It also allows the roots to 'travel'
and seek out this air and ready supply of
matter/humus also breaks down (rots away) and
releases nitrogen into the soil, which is
absolutely vital to plant growth. The ultimate in recycling! You put
all of your dead plant/vegetable matter into the
soil; it breaks down into Nitrogen which is the
main ingredient needed for new plant growth.
that any organic matter you add to the soil is
already on the way to rotting! All plant
and vegetable waste should be 'composted' first,
before being added to the soil. Peat, composted
bark, rotted stable manure and the like are all
ready to use.
ACID OR LIME
you should now know whether you have a sandy, loam or clay soil. You
should also be aware of any organic content in your soil. All of this
will have shown up in our simple 'coffee-jar' test.
will need to know if your soil is acid or alkaline
(or neutral). An Acid Soil does not have much - if
any - lime in the soil. An Alkaline Soil does have
lime in it - to varying degrees. A Neutral Soil;
well, it has lime in it, but not enough to class
it as an alkaline soil.
get a cheap basic testing kit at most garden
centres to tell if your soil is acid or alkaline -
and to what degree. (You can also do a basic test
by drying a teaspoonful of soil, and then sprinkle
some vinegar on it. If it bubbles, it will
probably have lime in it. If is doesn't it will
probably be acid or neutral!)
need lime in the soil to live and thrive.
Rhododendrons, Camellias, Ericas and a few others
do not. In fact the presence of lime in the soil
will make them quite ill - probably terminal!
encourages soil life, for the bacteria that sorts
out your organic matter into Nitrogen, are quite
lethargic in acid soils.
improves the 'tilth' (crumb structure' of heavy
soils such as clay soils. A really sticky
clay soil can be put right quite dramatically with
a dressing of lime. The lime coaxes the individual
clay particles to form 'groupings, allowing
moisture to drain, and plant roots the freedom to
act as a deterrent for some pests - slugs and
leather-jackets are not keen on lime. It will also
act as a preventative for club-root in brassicas.
the soil is good for earthworms. Most soils will
benefit with a high earthworm population. As well
as helping to break down raw organic matter, they
make a network of drainage channels in the soil -
great for heavy clay soils.
'garden' lime - Always read the instructions.
Garden Lime - NPK
Problems with Garden Soils |
By David Hughes -