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Ch. 2, pp. 13 - 14
[Soils: soils | properties | classes | caliche | depth | components | pH ]

Conquering Home Yard Caliche
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 carbonate, CaCO3).

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.
  1. 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.
  2. 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 growing plants.
  3. 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 adequate.

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.

  1. 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.
  2. If possible, remove the caliche before planting. Make planting holes large enough for a mature root system.
  3. Before planting, make certain water drains from the planting hole.
  4. Replace the caliche with good top soil or a soil mix. Discard the caliche.
  5. Lawns should be grown only where there are at least eight inches of good top soil above the caliche.
Typical Hole Sizes Should Be:

Large trees

Small trees

Large shrubs

Small shrubs

Flower beds
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

Diag 1

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