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| My simple worm bin |
Although it seems like desert soils would not be suitable
for vegetable gardening, the reality is all they lack is water to be
productive. However, to make these soils more water efficient, and to replenish
nutrients used in growing plants, amendments are necessary for all types of
desert soils. I will only be discussing organic methods in this section.
Sandy soils are
the most challenging and ‘needy’ when it comes to amendments. The addition of organic matter is necessary
to help these soils maintain a moisture level conducive to growing healthy
plants.
Clay soils hold moisture far better than sandy soils, but if
the clay is very heavy it can hold too much water and can cause root rot and
other problems. The addition of organic matter in this case is to provide
better drainage and aeration of the soil, both essential to healthy plant
growth.
The best types of amendments come from animal sources. Although
chicken manure, bat guano, fish emulsions provide nitrogen to feed plants, they
do not contain other essential nutrients (such as potassium, potash, calcium
and carbon to name a few) which is depleted from the soil after every growing
season. The goal is not just to feed the garden soil, but to create a soil
structure which supports healthy plants, reduces the amount of water needed, increases
beneficial soil microbes, attracts beneficial insects and soil building
organisms such as earthworms. The best way to tell if your garden soil is being
tended to properly is the appearance of earthworms. You can’t just add them to
your garden and hope they will multiply. In most areas of the country, “if you
build it, they will come.” However, I’ve been informed by the University
of Arizona this is rarely the case
in the desert as earthworms are not endemic here. So what’s a gardener to do?
Make an earthworm bin and use their castings. It’s much easier to maintain a
stable environment in a bin than it is in your garden.
Adding animal manures such as from steer or horses also
provides organic matter that helps sandy soil hold moisture and improves
drainage in clay soil, providing low levels of nitrogen to feed the plants.
Never add clay soil to sandy soil. This makes cement, which is certainly not
the goal here! Also important is adding straw. Although straw does require
nitrogen to break down, adding it along with the manure several months before
planting will start the decomposition process and also allow the manure to
‘age’ before planting. This is important as some manures contain high levels of
salt (from feed) that needs to be leached out prior to planting to avoid
burning new plants. I purchase both steam sterilized steer manure and straw way
ahead of my needs, and allow it sit for at least 6 months or longer before
using. Horse manure can contain weed seeds and sometimes Bermuda grass (which
you definitely don’t want in your garden), so be careful of using unless you
have the time to sterilize it yourself, by placing heavy weight clear plastic
over a pile and letting it cook in the hot summer sun for a few months. This
will kill off most seeds.
Of course, don’t forget compost. If you aren’t composting
and you want a garden, you need to start. Compost bins can make life easier,
but are not necessary. I’ve always composted directly in my garden, as turning
piles and keeping them moist is just too much work. I bury kitchen scraps
(vegetable and fruit trimmings, egg shells (in moderation), and other plant
matter (no meat, dairy or fish) in between rows. That’s it! Nature will take
its course.
