Blueberry Facts that Affect Crop Management

Blueberries are adapted to low pH and nutrient-poor soils. They grow reasonably well at soil pH 4.0 - 5.2, but the optimum pH is 4.3 - 4.8 . Soils should be amended with sulphur before planting blueberries to reduce pH (see publication #360, Fruit Production Recommendations, page 100). Elemental sulphur reacts with the soil to form sulphuric acid, thus reducing soil pH. This is a slow reaction, taking a year or more. Iron sulphate is faster acting, but more expensive.

Blueberries are susceptible to iron deficiency (Figure 1). This nutrient becomes less available for uptake when soil pH increases. In fact, iron deficiency symptoms on blueberries are a good indication that pH is too high. Iron deficiency symptoms will disappear with foliar application of iron chelate sprays. However, soil pH should be reduced to correct the problem in the long term.

Figure 1: Iron chlorosis on highbush blueberry leaves. Reducing soil pH will prevent this problem. Foliar sprays of iron chelates provide short-term control. Source: Michigan State University Extension

Blueberry roots do not have root hairs. They have a small surface area for nutrient absorption, and are relatively inefficient. They are very sensitive to waterlogging and to drying out. However, blueberry roots are associated with naturally occurring, very specialized fungi, called mycorhizae, which improve nutrient uptake.

There is little lateral translocation of water and nutrients within the plant. This means that irrigation should moisten entire root zone, not just a portion. Spread fertilizer evenly on both sides of the bush.

Blueberries are picky eaters. Roots are sensitive to nitrate fertilizers and chlorides. Ammonium sources of N, such as ammonium sulphate or urea are preferred over nitrate forms. Avoid using muriate of potash (KCl) on blueberries. Choose sul-po-mag or potassium sulphate instead.

Blueberries respond to organic matter and mulch. These improve soil structure and buffer against drought stress. Research by Dale and Ricketson (Figure 2) confirms this in Ontario.

Figure 2: Blueberry yield (6 year total) increased when peat was incorporated at planting and when the planting was mulched with sawdust.

Blueberries do not take up nitrogen until leaf tissue is present. Early spring applications of nitrogen are not used by the plant. Nitrogen applications should be split 3 ways, coinciding with bud break, bloom and early July. Very little nitrogen is required in the early years of the planting. See Publication #360 for recommended N rates. Use leaf analysis and plant growth to adjust N rates. Increased rates will be required if the planting is mulched

References on blueberry crop management:

• Managing the Nutrition of Highbush Blueberries, Extension Bulletin E-2011 Eric Hanson and Jim Hancock
• A Year in the Life of a Blueberry Bush, Mark Longstroth, District Horticultural and Marketing Agent, Michigan State University Extension

Source: Soil Management and Irrigation studies with Highbush Blueberries, Dale, Cline and Ricketson, Acta Horticulture 241, 1989

Related Links

• Managing the Nutrition of Highbush Blueberries, Michigan State University Extension
• A Year in the Live of a Blueberry Bush, Michigan State University Extension
• OMAFRA Berry Index Page

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