Fine-tuning blueberry nutrition for optimal yield and quality

Blueberries are a challenging crop to cultivate, as the plants don't readily absorb key nutrients, and the berries can therefore vary in flavour, quality and size. With an increasingly picky market, farmers need to optimise plant nutrition to obtain a consistent crop that commands high prices. Lindi Botha spoke to Dr David Marks.

- Dr David Marks

FAST FACTS 

• Blueberries have no hair roots and therefore struggle to take up nutrients.
• Calcium can only be applied for a limited period.
• Nitrogen must be applied in the right form in order to maximise production of fruit.

Blueberries are a relatively new crop to South Africa, and with the frequent arrival of new varieties, finding the right recipe for optimal production is no easy matter. At the same time, the price of blueberries is decreasing after hitting a peak two years ago, which means that farmers now need to make the most from every input and hectare to ensure their sustainability.

Unfortunately, their task is made far harder by the blueberry plant’s notorious inefficiency at absorbing calcium (Ca) and nitrogen (N), both of which are key elements required for a good fruit crop. Simply adding more of either nutrient doesn’t solve the problem. Instead, growers are advised to relook at application rates and methods, and the different forms of the elements.

CALCIUM

An adequate level of Ca improves both the quality and shelf life of blueberries. Low Ca levels, however, have far more to do with the crop than with fertiliser.

Dr David Marks, a founder of UK-based Levity Crop Science, says that to understand why Ca applications are inefficient, farmers need to understand three basic rules on plant Ca metabolism: capacity, transport, and absorption. “Plants cannot store excess Ca as they can other nutrients, such as potassium. When the holding sites for Ca in cell walls are full, plants precipitate any extra Ca being absorbed. Often, plants that are deficient in fruit still precipitate Ca from their leaves.