What Is the Soil pH Level for a Pistachio Tree?

pH Preference

• Pistachio trees grow best in a neutral to slightly alkaline soil. On the pH scale, this translates to a 7.0 to 8.0 as the pH level to aim for. You can determine the pH level of the area in which you'll plant your tree or trees by using a portable pH meter or a soil testing kit, both available from garden centers and mail-order suppliers. Some local extension services will provide a detailed analysis of your soil, including pH, when you send in a sample.

Significance

• Overly alkaline or acid soils can lock out vital nutrients that plants need. For pistachios, an excessively high pH level prevents the trees from taking in adequate zinc and copper. Zinc and copper both promote healthy foliage, while zinc is additionally responsible for proper flower and nut set. Low zinc, in particular, can be especially problematic in major pistachio-growing areas, which tend to have a high pH. If your soil tends to be acidic, on the other hand, the major risk from low pH is boron deficiency. Of all the nut trees, pistachios are most vulnerable to boron deficiency, which can lead to poor flower and nut set.

Correcting pH

• A soil test will tell you if you are are coping with either an acidic or alkaline soil that falls outside of the trees' preferred comfort range of 7.0 to 8.0. Ground limestone is the common amendment for raising pH, while sulfur can lower it, when needed. Scatter the needed amendment on the soil surface and water the area well, or work it into the top 10 to 12 inches of soil, along with other nutrients you may be adding. It's best to add soil amendments several months before you plant pistachio trees, because pH changes slowly.

Amounts

• If you are preparing a 100-square-foot area -- about the size for one mature tree -- calculate how many points you'll need to raise or lower your soil pH. For every 100 square feet and every 1 point you need to raise pH, work 5 pounds of limestone into the soil. To lower pH, work 1 pound of sulfur into the soil for every 1 point you need to lower it, per 100 square feet.