Doubling Olive Yields Possible — Research

New Zealand olive yields can be more than doubled by using fruit tree management techniques instead of more traditional methods.

That’s the findings of a three-year research project commissioned by Olives New Zealand.

The project aimed to increase yield – typically less than 10kg per tree – to 15kg.

But it exceeded expectations, achieving yields of 20-35kg per tree.

The project, supported by the Ministry for Primary Industries (MPI) through its Sustainable Farming Fund, brought together Dr Stuart Tustin, a Plant & Food Research fruit tree physiologist, and Andrew Taylor, an olive industry consultant – both of whom have extensive knowledge in stone, apple and pear culture.

They suggested applying the methods that work for stone fruit crops, including more aggressive pruning, a proactive spraying programme every 21 days, and thinning crops after the fruit has set to mitigate biennial bearing (in which light and heavy crops tend to alternate year on year).

Olives New Zealand executive officer Gayle Sheridan says that, contrary to some misconceptions, olive trees thrive in New Zealand. She says they grow more vigorously than in traditional olive growing regions, which often have more arid growing conditions.

“The trees were getting out of control – they grow too well in New Zealand, making harvesting a challenge,” Sheridan said.

“NZ’s olive trees don’t have problems with pests. Our biggest issue is the trees getting diseases – such as peacock spot, cercospora and anthracnose – due to our often rainy climate, which requires a different approach.”

New Zealand has about 300 productive olive groves, encompassing more than 2000 ha. The main growing regions are on the east coast from Northland to Canterbury, as well as Kapiti and Central Otago.

The project trialled Tustin and Taylor’s recommended techniques on five olive groves, one in each major growing region. The results, even after the first year, were so dramatic that the growers hosting the trials insisted on extending the methods to their entire groves.

“We had to compare our results to the typical regional averages as we couldn’t persuade our trial growers to keep their control sites,” Sheridan told Hort News.

“Once diseases began to be controlled, we found we were able to grow large clusters of olives for the first time – like bunches of grapes. In addition, feedback from international visitors has been outstanding, with visitors commenting that they’ve never seen such healthy olive trees,” she added. More