Agriculture Reference
In-Depth Information
Many lack one or more primary nutrients and any number of
trace minerals.
Soil for agricultural use needs to hold water without
becoming waterlogged. Sandy soils are seldom waterlogged,
but they dry out so quickly that constant watering is required.
They make root growth easy but don't hold on to nutrients
very well and are low in organic content or humus. (There is
some dispute among experts on the exact definition of humus.
For our purposes, it can be defined as organic matter in the
soil that has reached a point of being sufficiently stable that it
won't easily decompose further. Thus, finished compost and
humus are identical for our purposes.) Clay soils will be
waterlogged in the winter and will remain waterlogged as
long as water comes to them. As soon as the water stops, they
bake and crack, putting stress on root systems. Clay soil is
clingy, sticky, and nearly impenetrable to roots. Loam soil is
closest to the ideal, as it consists of a mix of sand and clay
with a good amount of humus that helps it retain water and
nutrients in proportions suitable for agriculture.
Both sandy and clay soils can be improved with vermiculite.
Vermiculite is manufactured by heating mica rock in an oven
until it pops like popcorn. The result is a durable substance
that holds and releases water like a sponge and improves the
water-holding characteristics of practically any kind of soil.
Because it is an insoluble mineral, it will last for decades and
possibly forever. If the soil in your bed isn't loamy to start
with, adding coarse or medium vermiculite at the rate of four
to eight cubic feet per 100 square feet of raised bed will be
very beneficial. (Vermiculite costs $4 per cubic foot in
four-cubic-foot bags at the time of this writing.)
