Success with Blueberries

Gordon Johnson, Extension Fruit & Vegetable Specialist;

There has been an increase in interest with blueberry production in Delaware over the past 5 years. Blueberries can be a very profitable crop, especially for growers that direct market. As a perennial shrub-like crop, blueberries will take 5 or more years to come into full production but can be productive for decades. It is critical therefore to make sure that plants get off to the right start. Blueberries have exacting soil modification requirements that must be addressed. They are native to areas with acid soils that have high organic matter in the surface but with sand below and with water relatively close to the surface. However, they do not tolerate waterlogged soils.

There are 5 key factors critical to establishing blueberries.

1) Acidify the soil. Blueberries require acid soils with a pH in the 4.5-5.2 range (target 4.8). Most of our cultivated soils have pHs much higher than this. Therefore soils must be acidified. The material commonly used to acidify soils is elemental sulfur. However, sulfur must be converted by microorganisms to release the acidity so it acidifies only when soils are warm. Plan one year ahead of time to acidify the soils. On a sandy loam soil, about 1000 lbs of sulfur per acre are required to lower the pH to the desired level. You should not plant until the soil has been acidified.

2) Provide good drainage. Make sure that water drains away from the planting site and does not collect. It may be necessary to make low, wide ridges to improve drainage and move excess water away from plants. Avoid planting in sites that are poorly drained or that have high water tables in the winter.

3) Increase organic matter in the area that is to be planted prior to planting. This is commonly done through the addition of materials such as peat moss mixed directly into the planting hole (mix at one gallon of peat with backfill soil for each plant during planting). You may also use other materials such as composted saw dust, bark fines, or other partially rotted materials as long as they are acid (have low pHs). You can use up to half by volume of these materials mixed with soil in the hole. Do not use manures, high pH composts, or spent mushroom soil. You may also choose to modify the entire planting strip before planting. Apply 2-4 inches of these organic materials (such as composted sawdust or bark fines) and work them into the soil in a 3-6 foot strip where the blueberries are to be planted.

4) Mulch immediately after planting with a 4 inch layer of organic material. Common materials are aged sawdust or bark mulch. This mulch is critical to protect the shallow roots and provides additional organic matter as it decomposes (reapply as necessary).

5) Install drip irrigation and provide irrigation water through the drip as needed. Blueberries do best in moist (not wet) soil conditions. Drip tubing should be thick walled for long term use and should be placed under the mulch.

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