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| Our native desert willow is adapted to alkaline soil. |
The most significant affect pH (which stands for potential
hydrogen) has on plant growth is the availability of important plant nutrients.
It’s not that these nutrients aren’t there, although is some instances that may
be the case, but it’s that the pH affect the ability of plant roots to absorb
the nutrients they need for adequate growth.
At one time experts thought adding soil amendments such as
elemental sulfur or acids would alter the pH of desert soils. However, these
additions proved to have little effect, if any.
So what’s a gardener to do? The most important thing you can
do for your vegetable garden soil is to add compost. This will alter the soil
by increasing moisture holding capacity, drainage and provide necessary
nutrients for plant growth. However, this is much more difficult to do for
landscape plants, since the amount of organic matter needed for a mature tree’s
root zone would involve excavation of an area at least 5 feet deep and 2 to 3
times the height of a mature plant.
That’s a whole heck of a lot of soil to treat!
In landscape situations, the best solution is to plant
natives. Native plants have developed a tolerance to alkaline soils, and will
thrive without soil additives.
Another challenge of desert soil is caliche clay. You’ll
know you’ve got it if you can’t dig through it. Caliche clay isn’t just
hardpan, and there’s plenty of that around, this impenetrable layer requires a
jackhammer to remove. Not only will roots not grow through this clay, but water
will not permeate either. If you find the layer in the uppermost part of the
soil, abandon the spot and plant elsewhere, or in the case of a vegetable
garden, use raised beds. If you are planting a tree or shrub and find the layer
at the bottom of the hole, as long as you punch through so water can drain,
you’ll be fine. However, if you find caliche in the root zone (1-3 feet down),
or you can’t get through it, don’t plant there.
