|Many southern Arizona soils have layers of caliche either
on or under the surface. Caliche is a layer of soil in which the
soil particles have been cemented together by lime (calcium
Caliche is usually found as a light-colored layer in the soil or as white
or cream-colored concretions (lumps) mixed with the soil. Layers
will vary in thickness from a few inches to several feet, and
there may be more than one caliche layer in the soil.
What Does Caliche do to plants?
Caliche causes three problems in the yard or garden.
- The caliche layer can be so tight that roots cannot
penetrate through it. The result is that plants have only
the soil above the caliche to use as a source of nutrients
and water and normal root development is restricted.
- The same conditions that restrict root penetration also
reduce water movement. Water applied to the soil cannot move
through the profile if a restrictive caliche layer is
present. The restricted water penetration can contribute to
problems arising from inadequate root aeration and can lead
to accumulations of salt in the soil surface. Both problems,
lack of aeration and salt accumulation, reduce the vigor of
- The pH (acidity or basicity) and free calcium carbonate
in a caliche soil are often high enough to cause iron to
become unavailable for plants. The symptoms of iron
deficiency are a yellowing of the youngest plant leaves
while the veins in the leaves remain green. The resulting
striping appearance is slightly different from that of
nitrogen deficiency symptoms, which are a general yellowing
including the veins of older leaves. Iron deficiencies are
additionally aggravated by the water saturation of the soil.
Check with country Extension agents for more information
about how to correct iron deficiency in the yard or garden.
How can Caliche Be Managed?
Try to keep plant roots out of the caliche zone. Successful home and
horticultural plantings can be made by first removing the
caliche and replacing it with a soil mix. The hole for planting
should be large enough to accommodate the root zone system of
the mature plant. It should be dug completely through the
caliche layer so that water will drain from the planting hole.
If it is not practical to dig completely through the caliche zone, then
dig a chimney drainage hole through the remaining portion of the
caliche layer. This will provide a water drainage passage.
Check the planting hole for drainage before adding the plant and soil
mixture. Partially fill the hole with water. If the water level
drops four inches or more in four hours, the drainage should be
The planting hole can then be filled with a mixture of 1/3 wood residue
product, peat moss, or compost and 2/3 good soil (do not use
uncomposted manure). Discard the caliche that has been removed.
Keep the consistency of the soil mix the same throughout the
planting hole and drainage chimney.
If a lawn is to be grown over caliche, provide at least eight inches of
good top soil above the caliche.
- Caliche can cause plant growth problems by:
- Restricting root penetration and rootment.
- Restricting water penetration, resulting in poor root
aeration and potential salt accumulations.
- Causing iron to become unavailable to the plants.
- If possible, remove the caliche before planting. Make
planting holes large enough for a mature root system.
- Before planting, make certain water drains from the
- Replace the caliche with good top soil or a soil mix.
Discard the caliche.
- Lawns should be grown only where there are at least eight
inches of good top soil above the caliche.
Typical Hole Sizes Should Be:
Size of Hole
6' deep 6' diameter
5' deep 5' diameter
3' deep 3' diameter
2' deep 2' diameter
1 1/2' deep 1 1/2' wide