Basic principles of blueberry nutrition

Blueberry agronomic principles

Blueberry plants are known to be in the soft fruit market, but actually, they are not exactly soft fruits. Blueberries are more bush fruits, sharing many of their characteristics with Currants and Gooseberries.

The blueberry plant is more acid-loving than most of the soft fruits, enjoying pH as low as 4.5 to 5.5. This optimum is a far cry from normal UK soils at average pH of 7.8 and for this reason, most UK blueberries are pot grown, in a peaty coir substrate mixture.

Blueberry has a fine and fibrous rooting system and no tap root, it is better to think of its rooting system as a carpet or mat. The mat is located approximately 4 cm below the soil surface and 80% of the root mass is within the top 16 cm of the soil. For this reason in field-grown blueberry crops are normally tended to with flotation tyres or low-pressure transport systems, so as not to damage the roots.

In a potted growing system as we have in the UK the matt root comes to encompass the whole of the pot. The size of the pot increasing with the age of the plant helps both nutrient uptake and allows the blueberry to better stand. Old blueberry plants in medium pots have a tendency to roll over if not supported, be it high winds or mechanical interference.

Blueberry nutrition

Blueberry nutrition and fertigation is very much a consequence of the rooting system and pH range. Ammonium nitrate is the preferred nitrogen source since this lowers the soil pH through nitrification, to the benefit of the blueberry. The blueberry plant prefers ammonium as it binds to the soil and does not leach through as nitrate would.

Blueberry roots remember are fine and fibrous, meaning uptake is slower, compared to more vigorous rooting systems like strawberry and raspberry. The blueberry plant can take up as much N as other plants as they have a much larger root mass overall. Blueberry struggles to take on immoveable nutrients like Calcium, due to the pH range.

Calcium is detrimental to blueberry as it raises the pH range and causes problems with the brittleness of the peduncle. This leads to blueberries dropping fruits early if disturbed, where normally a less brittle peduncle, can retain the berry in high winds or other disturbing situations.

Basic blueberry fertigation

For young and small plants the focus should be to push vegetative growth forwards with a balance of ammonium and nitrate N complimented with P&K plus micronutrients to nurture the plants and develop robust root systems.  Typically YaraTera Kristalon Lilac (20-8-8 + micronutrients ) would be recommended for young plants often using a single tank system. Newer plants may stay on the single tank system for 3-4 years before moving to the two-tank system, although some newer specialist varieties may make the switch in 1-2 years.

For more mature plants the focus is on a heavier feed programme to support fruit production and flowering habit. This requires a more balanced nutrition so typically a two-tank system with YaraTera Amnita L (18-0-0) in Tank A and  YaraTera Kristalon Brown (3-11-38 + micronutrients ) or YaraTera Kristalon Scarlet (7.5-12-36+ micronutrients ) for medium flower situations.