Typical soil pH in the Phoenix area is about 8.5. This is ideal for native plants like mesquite and palo verde but very hard on most everything else. Even for plants that are not pH sensitive this high pH makes the nutrients in the soil unavailable. Lowering the pH to 6.5-7 will enable plants to use the nutrients that are in the soil.

Plants

The root exudates of each plants have a certain pH.

Organic Matter

Adding organic matter to the soil is the best long term solution to neutralizing the pH. Mixing compost into the soil, keeping mulch on top of the soil, and adding beneficial organisms like mycorrhiza and other microbes will increase the organic matter in the soil over time.

Note that earth worms are invasive species. Earthworms are not native to Arizona. It might not be a good idea to add new species of earthworms to compost or soil after all.

Agricultural Sulfur

Also known as Soil Sulfur can be used in addition to increasing organic matter. Recommendations I have heard from people more experienced than my self are:

• 1 table spoon per square foot 3-4 times per year (Shamus O’Leary). This is about 1lb / 27 ft²
• 1lb / 100 ft² (Tony Sarah)
• add 5lb to the back fill when planting trees up to 15 gallon pot size (Tony Sarah)

My front yard is 3,000 ft². I measured Arizona’s Best brand soil sulfur density to be 0.598958333 lbs/cup. Tiger CR90’s label says its density is 76 lb/ft³.

Links

• Mango and Tropical Fruit Tree Care in a High pH Environment
• Tiger CR90 label