Know your soil

The soil in our gardens is a mixture of
mineral particles derived from rock
weathering over millennia, air, water,
decomposed organic matter and living
organisms. Though all soils are based on the
same basic ingredients, they vary widely
because of differences in the way the
ingredients are combined.

Soils may vary in the size of their particles
(texture), the way the particles stick together
(structure), and the amount of space between
the particles (porosity). They can be roughly
grouped into three main types: sand, clay and
loam. All soils are a mixture of characteristics
and even within your garden you will have
differing mixtures in various places.
Soil texture can range from coarse sand or
even gravel at one extreme to pottery-quality
clay on the other, with silt coming in the
middle. Soils can be waterlogged or freedraining,
have a hard crust or clay pan, have
too few or too many of some minerals, be rich
in organic matter and nutrients or deficient,
be alkaline or acidic, and even be saline.
To ensure our plants thrive and our
gardening practices constantly nurture and
replenish the soil instead of slowly degrading
it, every gardener needs to know some simple
soil science.

Texture
Soil texture refers to the size of the soil
particles and is determined by the type of
parent rock from which it originated.
Sandy soils are made up of coarse particles
with a lot of air between them. Both wet and
dry sand feels gritty between the fingers. Such
soils allow water and nutrients to dissipate
very quickly.
Clay soils are made up of very fine particles
with not much air between them. The
particles cling together and can retain water
too well, resulting in waterlogging. Nutrients
can be tightly bound to the fine particles, to
the extent that they might be unavailable to
FABULOUS 56 FOOD FROM EVERY SMALL GARDEN
plants. Clay is hard when dry, and greasy,
rubbery or sticky when wet.
Silt is finer than sand and coarser than clay
and may feel powdery when dry. Wet silt may
feel slightly sticky or plastic; this is because of
a film of clay adhering to the silt particles.
Loamy soil has a good balance of sand, silt
and clay and adequate humus content from
decomposed organic matter. Loam is usually
considered to be the best type of soil for
gardening, but there are myriad gradations
and varying amounts of organic matter, air
and water. Clay loam might have too many
fine particles and still become waterlogged,
whereas sandy loam could have enough of the
larger particles to remain too porous.