Caliche - Hard Desert Gardening
Don't Give Up Hope. There Are Solutions.
Caliche is also known as hardpan, calcrete, duricrust or in India, kankar. It is actually a form of calcium carbonate. The word is Spanish, but comes from the Latin word calx, which means limestone.
Caliche may be found a few centimeters under the surface or it may be buried in sand, and dust up to two meters below.
It can be a few centimeters thick or many meters thick. It occurs all over the world in deserts and semi-arid areas. The Kalihari and Sahara Deserts have large deposits of caliche, as does the Arabian Peninsula, western and central Australia, and the southwestern deserts and high-plains regions of the U.S.
The problem with caliche is that it acts as a barrier, stopping precipitation from percolating down into the soil. Now, if you've got eight inches to a foot of topsoil, however poor it may be, and you want to plant some small shrubs, perennials and annuals that need no more than that to grow their roots, then you're okay.
But, if you're going to plant a tree, or any deep-rooting vegetation, then you've got a problem.
Many gardeners use a pick axe to break through the caliche layers, but, if the caliche is two to three meters thick, that can be a back-breaking job. Some gardeners use a caliche pole, which is simply a long, solid steel pole, sometimes pointed at the business end. They pound the pole into the ground to break through the caliche layers, and then dig and pick axe around the hole.
As one who has dug holes in caliche, it is a long, tiring task that I would much rather leave to a backhoe, or some other mechanical device.
But exactly what is caliche? It's not rock, although I have come across some rather large rock specimens bound in it. It's not really dirt either. It's sort of something in between. Known to scientists as calcium carbonate, it is mined in several parts of the world and is used in the manufacturing process of plastics, rubber, coatings, paper, pharmaceuticals, agricultural products, feeds, and...who woulda guessed...concrete.
Caliche is formed when ground water charged with calcium carbonate, rises through the soil and evaporates, leaving behind the calcium carbonate. Then wind-blown particles of calcareous dust accumulate on the top of the soils. Finally, hard, fast rains drive the particles into the soil. Precipitation water mixes again with the calcium carbonates, cementing gravel, dust particles, into a dense, almost impenetrable layer.
Now, any water from precipitation is prevented from percolating down past the caliche formation. And any groundwater is prevented from percolating up. Any water from rainfall now produces short-lived, but incredibly disastrous flooding, washing any remaining topsoil away.
To desert gardeners who like a challenge, caliche certainly provides it.
Caliche also generally adds alkaloids to the soil, resulting in high pH. This, combined with calcium carbonates present, can keep plant roots from obtaining the minerals and nutrients necessary for them to survive.
If you're a new desert gardener, or are just now getting down to caliche, then you'll want to make sure if you plant anything which requires a large and deep root system, that you dig a hole through the caliche layer in which to plant.
If you've got really thick caliche, then instead you might want to dig a hole in the caliche large enough to accommodate a mature root system of the tree. Then punch or dig one or several smaller holes through the caliche to insure drainage.
Before you plant, however, test the drainage of the hole. Fill it with water, and keep an eye on it. A water-level drop of one inch per hour is adequate for drainage.
As I said before, digging caliche is hard work. But if you persist, your efforts will be paid back handsomely by healthy, happy plants.
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