SOIL PH
Soil pH, or potential of hydrogen, is the garden fundamental that refers to the amount of acidity or alkalinity present in a given soil. Garden plants almost all range from 4.5 (extremely acidic - think blueberries, azaleas, hydrangeas) to 8.5 (extremely alkaline - think cacti, yuccas). Acid conditions are created by layers of decomposed organic material such as fallen logs and dense leaf drop in forests. Since the Mojave has the exact opposite conditions, we find ourselves at the other end of the pH spectrum at 8 to 8.5. Our desert plants love alkaline soil and we don’t need to change it by amending it, except for modifying soil that is unworkable, hard or coarse. Using too much amendment in a planting hole can actually make roots want to stay inside a pocket of yum instead of properly expanding outward in search of nutrients.
Aged compost or worm castings are ideal organic materials. Worm castings are compost that’s been processed through the digestive system of worms making it very broken down, ultra high in organic material, and quickly plant soluble. Good quality castings are NPK neutral (for you plant feeders out there) so they’re not too nutrient rich for desert plants like most plant foods. When combined with water they create humic acid which benefits soil structure.
Soil pH, or potential of hydrogen, is the garden fundamental that refers to the amount of acidity or alkalinity present in a given soil. Garden plants almost all range from 4.5 (extremely acidic - think blueberries, azaleas, hydrangeas) to 8.5 (extremely alkaline - think cacti, yuccas). Acid conditions are created by layers of decomposed organic material such as fallen logs and dense leaf drop in forests. Since the Mojave has the exact opposite conditions, we find ourselves at the other end of the pH spectrum at 8 to 8.5. Our desert plants love alkaline soil and we don’t need to change it by amending it, except for modifying soil that is unworkable, hard or coarse. Using too much amendment in a planting hole can actually make roots want to stay inside a pocket of yum instead of properly expanding outward in search of nutrients.
Edible plants are a different beast and most require heavy amending in the desert. They prefer acidic or neutral conditions. Layering native soil with leaves, twigs, broken down compost, coffee grounds, and alfalfa pellets are good ways of adding nitrogen and acidity. For those who want to learn more, this lasagna layering technique comes from a permaculture concept called Hugelkultur.
DEALING WITH SOIL STRUCTURE
The ideal soil for desert plants is one that holds moisture and still drains nicely. But sometimes we run into the two most extreme soil textures: jack-hammer hard or sandy as a sieve. With compacted soils, water runs off and roots can’t expand. In very sandy soils, water passes through too quickly and roots dry out. The way to alter either of these conditions is by sprinkling organic material into planting holes and back-filling with dirt. By doing so, a compacted soil opens up and absorbent material is introduced into overly porous soil.
The ideal soil for desert plants is one that holds moisture and still drains nicely. But sometimes we run into the two most extreme soil textures: jack-hammer hard or sandy as a sieve. With compacted soils, water runs off and roots can’t expand. In very sandy soils, water passes through too quickly and roots dry out. The way to alter either of these conditions is by sprinkling organic material into planting holes and back-filling with dirt. By doing so, a compacted soil opens up and absorbent material is introduced into overly porous soil.
Before putting your plant in the ground, fill the hole with water and observe how quickly it drains. It should drain in a few minutes on the first fill but start holding water by a second fill.
- If it doesn’t drain at all then your soil is clay, caliche, or compacted. Plant roots will sit in a bathtub of water and suffocate with normal watering. To prevent this, make an extra deep and wide hole and really loosen up the back-fill soil.
- If water drains instantly, your soil is too coarse and won’t retain enough moisture to sustain plants.
- In both cases, mix in roughly 30% organic material to your back-fill soil and moisten. The organic material will interrupt the blockiness of hard soil. In coarse sand, it introduces an absorbent element to help hold moisture. Amending in this way gives microbes something to grab onto and a way to start improving soil structure around roots.
Aged compost or worm castings are ideal organic materials. Worm castings are compost that’s been processed through the digestive system of worms making it very broken down, ultra high in organic material, and quickly plant soluble. Good quality castings are NPK neutral (for you plant feeders out there) so they’re not too nutrient rich for desert plants like most plant foods. When combined with water they create humic acid which benefits soil structure.
Weed-free yard clippings and twigs also qualify as organic material but be careful not to go overboard using yard waste since an overabundance of fresh compost can rob plants of nutrients while breaking down. Clippings and twigs offer a fast way to start changing the texture of problem soils. When using yard debris avoid material from plants that are allelopathic, meaning they produce biochemicals that discourage other types of plant life. Examples of allelopathic plants are eucalyptus, tamarisk, oleander, tree-of-heaven, and creosote.
Showing 1 reaction
Sign in with
Facebook