Note that the instructions in this section are generalized — you should use the instructions included with your specific pH testing kit.
Try to gather enough dirt in each sample that you have about a pint (0. 94 liters) or more in total. For most methods of testing, this is plenty.
It’s important to make sure your soil is completely dry before proceeding — moisture can cause an inaccurate pH reading.
Other types of kits exist as well, so be sure to use the instructions provided with your kit. For instance, some modern electronic testing kits determine a soil pH almost instantaneously via a metal probe. You can also collect a sample and take it into your county extension office for a free soil test.
Organic matter can also give your soil other benefits — most noticeably, improving its drainage and aeration. [3] X Research source
Depending on the starting pH of your soil, the amount of aluminum sulfate you should use can vary significantly. In very general terms, you should expect to use about 1. 2 pounds of aluminum sulfate to lower the pH of a 10-square foot patch of soil by one on the pH scale (e. g. , from 7. 0 to 6. 0, from 6. 0 to 5. 0, etc. ). [5] X Research source However, using too much additive can be harmful to your plant, so consult an online resource (like the one here) for more precise usage information. Do not use aluminum sulfate for large applications because it can lead to aluminum accumulation and aluminum toxicity in soil.
As noted above, compared to aluminum sulfate, you will generally need a relatively small amount of pure, sublimed sulfur to produce an equivalent pH change. In general, you’ll need about 0. 2 pounds of sulfur to lower the pH of a 10-square foot patch of soil by one whole number on the pH scale. [7] X Research source Consult an online resource (like the one here) for more precise usage information.
Sulfur-coated urea content will vary from fertilizer to fertilizer, so consult the instructions that come with your fertilizer to determine the right amount to use for your gardening needs. Sulfur-coated urea is a slow-release fertilizer that doses nutrients out slowly as your plants need them, rather than distributing them all at once.
Diammonium phosphate Ferric sulfate Peat Ammonium nitrate
Certain evergreen shrubs (e. g. , boxwoods, California lilacs) Certain deciduous shrubs (e. g. , lilacs, mock oranges, Forsythia species) Certain perennials (e. g. , pinks, hellebores)
The blue color of low-pH hydrangeas comes from the chemical aluminum. When the pH of the soil is low, it’s easier for the hydrangea to absorb aluminum from the soil, which shows in the flower petals. [14] X Research source
