Background
NZ Cherry Corp are an export cherry grower and packhouse located in Central Otago New Zealand, handled by General Manager Reece van der Velden. NZ Cherry Corp have approximately 70 ha of cherries across 4 orchards – Main Block, Leyser Block, Judare Block and Albany Heights. Three orchards are located adjacent to each other just outside of Cromwell with the fourth, Albany Heights, located 15 km away on the upper terrace at Mount Pisa.
The main cherry varieties grown are Stella, Romance, Kordia, Lapins, Sweetheart and Staccato. Older blocks are under a traditional central leader pruning system but new blocks are under the upright fruiting bush pruning system.
Despite it being an inland basin, the climate in Central Otago during the growing season can be variable. Evapotranspiration (ET) rates at budbreak are typically around 2.5 mm day and build to an average of 5 mm per day at the peak of the season, however prolonged periods >6 mm a day are common. They then drop back down to 2 mm day by leaf fall. Annual rainfall is typically around 375 mm and is evenly distributed over the growing season, with the winter and early spring (July through September) being the three driest months. Bud-break in Central Otago is mid-September through to early October, harvest is from mid-December through to early February, while dormancy is from April onwards.
The soil types range from deep silts of moderate to high water holding capacity through to shallow sandy loams with high stone content that are of low water holding capacity. Irrigation is by micro-sprinklers that are designed to apply 3 mm per hour per hectare. Good irrigation management is critical for cherries year-round but with a particular focus required from fruit set through to harvest.
The goal is to maximise premium export fruit which requires firm cherries of good size (at least 26 mm) and colour. Fruit firmness is key for the Asian market and is New Zealand’s point of difference.
Soil Moisture Monitoring
Primary Insight first started working with NZ Cherry Corp during the 2023-24 season when five 90 cm Drill & Drop Moisture Probes with IoT DTUs were installed.
Challenges were initially encountered regarding placement of the probes in relation to the sprinklers, particularly on the sandy soil types of low water holding, i.e., the probes reacted to rainfall but not irrigation events. It was observed that some micro-sprinkler systems can have a dry spot in their immediate vicinity, and where the irrigation design has limited or no overlap. But these challenges were worked through adjusting sprinkler placement and in a couple of instances reinstalling the probes, so they gave reliable readings.
Subsequently another four 90cm probes with IoT DTUs were installed during the 2024-25 season.
As part of the Summerfruit NZ irrigation trial in 2023-24, Primary Insight undertook an international literature review of best practice irrigation strategies for cherries. From this it was concluded maintaining soil moisture levels around 80% of field capacity from budburst through to harvest was critical. This maximises fruit size and firmness while also minimising the likelihood of cracking (splitting) from rain events. Post harvest reducing soil moisture levels down to the soil’s stress point and irrigating to replace daily ET was the recommended approach. This terminates vegetative growth and instead puts the trees energy into bud development. A small and frequent irrigation strategy is also preferable, particularly in the lead up to harvest.
The irrigation refill points were adjusted for the 2024-25 season to reflect this.
An example of the irrigation practice changes made from the 2023-24 to 2024-25 season can be seen in the soil moisture graphs below alongside the root activity graph for this period.
Figure 1: Soil moisture trace graph on IrriMAX Live
Figure 2: Root activity graph on IrriMAX Live showing 2023-24 versus 2024-25 season
The Benefits
The above change in irrigation practice has resulted in better-quality fruit and an increased export pack out.
The fruit is still of good size and colour, but is firmer and has much greener stems, there is also less fruit being rejected or only being fit for domestic sale.
These observations are reflected by the latest 2024-25 season SummerfruitNZ irrigation trialwork. The two trials have shown following the recommended irrigation practice increased export pack out by approximately 10% from the under and over irrigation sites.
“Primary Insight have been great to work with, they ensured all our Sentek probes are installed correctly and that the soil moisture graphs are correctly set. They also ran an irrigation workshop for our staff. Everyone now has a good understanding of the importance of getting irrigation right, how to read the IrriMAX Live graphs and when we need to irrigate. We are very pleased with our investment in Sentek soil moisture probes, alongside the support we get from Primary Insight, and looking forward to the continuation of this successful partnership.” -Reece van der Velden
Figure 3: 2024-25 season irrigation trials showing pack out percentage for export, domestic and reject fruit under different irrigation practice
Figure 4: 2024-25 season irrigation trials showing pack out percentage for export, domestic and reject fruit under different irrigation practice
