An AHDB-funded project investigated nitrogen application for pot-grown blueberries to ascertain optimum application timing for maximising yields while reducing the risk of frost or cold injury to bushes and flowers.
The varieties Duke and Aurora were included in the investigations. In the first year of the project, three different levels of nitrogen feed (60mg/l, 120mg/l or 180mg/l) were applied throughout the season from March until October. In the final three years, the use of high-nitrogen (180mg/l) and low-nitrogen feeding (60mg/l) applied in the autumn, spring or summer growth periods was compared. During the periods when high/low feeding was not applied, an intermediate level of 120mg/l was used.
Little effect was seen from varying nitrogen levels throughout the season or for periods within the season. There were no adverse effects on plant growth or yield at the highest nitrogen concentration of 180mg/l and it would appear that levels of 60mg/l would be adequate for blueberries because nitrogen is not a limiting factor at this low regime. However, there were indications that there was also some consistency in maintenance of improved Brix, percentage of marketable fruit out of store and class-one yields over the seasons for the following regimes:
- Aurora: autumn low/spring high.
- Duke: autumn low.
Results show that, in general, lower levels of nitrogen are sufficient for pot-grown blueberries that could give rise to cost savings across the season.
The full report for project SF137 is available online at horticulture.ahdb.org.uk.
For details on all AHDB Horticulture activity, see horticulture.ahdb.org.uk.