Nutrient uptake in a challenging environment

Claire Scofield is a recipient of a NZ Fruitgrowers’ Charitable Trust postgraduate scholarship 2024. Her research investigates the effects of environmental conditions under rain covers on calcium uptake in cherries. She aims to deepen the understanding of xylem dynamics and the impact of rain covers on these processes, exploring mitigation strategies through vegetative management, nutrient applications, or plant growth regulators. Funded by Hort Innovation and supervised by the University of Tasmania with half of the field research conducted in Central Otago and supported by Plant & Food Research, this study benefits both Australian and New Zealand growers dealing with similar fruit quality issues.

How well are calcium dynamics understood in stonefruit compared to pipfruit?

Calcium dynamics are much better understood in apples than in cherries, largely due to the significant impact calcium deficiency can have on apples, especially through disorders like bitter pit, which severely affects pack-outs. In cherries, the role of calcium is less clear. While calcium is believed to contribute to fruit firmness and post-harvest quality, many other factors also play a role. Research in cherries is limited since there is no direct consequence of low calcium levels beyond potential quality issues. A key difference between apples and cherries is the duration of xylem functionality – which is 30 to 40 days in cherries compared to 60 to 80 days in apples – making the timing in cherries even more critical. While calcium is a central focus in my project, there is room to explore other factors as the research evolves.

What key findings can you already share about cultural practices?

The first year was primarily about testing methods, but one of the most intriguing findings was related to increasing calcium movement into the fruit through the removal of new vegetative growth. By removing all actively growing shoots over a season, we saw an average increase of around 30 percent in fruit calcium levels. While this increase is significant, the treatment was quite extreme, and it’s not something we would be recommending for growers to implement. However, this year, we're exploring a much milder approach by introducing a very early summer prune (before 40 days after full bloom (DAFB)) to see if it produces a similar effect – this might be something growers could realistically adopt. It's a starting point to understand more about timing, and when are the most critical time points for ensuring uptake.

Are more growers moving to rain covers and protected cropping?

Yes and no. Most growers would agree that rain covers can make the difference between harvesting a crop or losing it during a high-rainfall season. However, the cost of installing these covers, especially over large blocks, can be prohibitive. The uptake of rain covers in both New Zealand and Tasmania seems to be at a similar level. In Tasmania, growers tend to put out their rain covers during flowering to encourage better fruit set. Thanks to the warmer temperatures and dryer conditions after rain, bees are still able to pollinate.

How have you split your research on both sides of the Tasman?

I've been fortunate that growers in both New Zealand and Australia have been really open and willing to engage. In Australia, I've been working with a grower to carry out field trials, and they have been very accommodating, even with some of the unconventional practices we have introduced into their orchards. In Central Otago, I have a few growers who are always happy to chat, share ideas, and offer feedback, which has been invaluable. With support from both sides of the Tasman, I believe there's a shared understanding that this type of research will benefit growers facing the challenges of changing environments and how to adapt. I was also fortunate to attend and present at the Australian National Cherry Industry Conference, where a number of New Zealand growers were also in attendance.