Answer: An acid soil with a pH between 4.5 and 5.5 is considered ideal for highbush blueberries. For most soils, the pH must be lowered (made more acidic). Test soil pH a year before planting because acidification, if necessary, takes more than 6 months. If the pH is between 5.7 and 6.5, acidify the soil by adding finely ground elemental sulfur (S) to the soil before planting. The amount of S needed depends on how much the soil pH needs to be lowered and the soil type.
To lower the pH from 6.5 to 5.4 in a clay loam soil, apply 3.5 to 4.5 lb S/100 sq ft.
To lower the pH from 6.1 to 5.4 in a clay loam soil, apply 2 to 2.75 lb S/100 sq ft.
Heavier soils may require more S for a similar amount of acidification.
It?s best to use the lower rate initially, check soil pH again in 6 months to a year, and apply more S only if necessary. Do not apply more than 7 lb S per 100 sq ft at one time.
If the pH is between 5.5 and 5.7, mix in Douglas-fir sawdust and ammonium sulfate fertilizer before planting. These materials will acidify the soil. If the pH of an organic soil is higher than 6.5, it?s usually not practical to acidify it enough for growing blueberries.
In some cases, soil pH is too low for blueberry production. If the pH of your soil is below 4.0, incorporate finely ground dolomitic limestone at a rate of about 5 to 10 lb/100 sq ft.
The bottom line is that you'll need to have your soil tested so you know what the current pH is and how much you'll need to change it.
Best wishes with your blueberries!
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