Case studies

Optimising irrigation

Chris Smallwood has a 4Ha avocado orchard in Katikati. He has owned the orchard since 2017 and it has 244 trees, 180 producing Hass trees and 64 non-producing (16 months old).

When Chris took over the orchard, approximately 60% of the trees were in ‘poor’ condition. He was concerned that the volume of water being ‘pumped’ into the orchard for frost protection was impacting tree health. In addition, the amount of water the system was using meant that the orchard was exceeding the consented volume of water allowed to be taken from the bore.

The original irrigation system was used for frost protection and irrigation and drew water from the bore at 29oC. The frost protection system ran off one thermostat with the pump running continuously through the night as it cycled through three zones. In total the system would pump 80,000-90,000L of water per night into the orchard.

Chris monitored and optimised the orchard irrigation and frost protection system by:

  • measuring the temperature difference in the orchard. He identified a 4oC difference between the ‘bottom’ block and the ‘top’ block.
  • changed the irrigation nozzles from 115L/min to 75L/min and 30L/min depending on requirement.
  • installation of a PLC (programmable logic controller) and additional thermostats resulting in the irrigation now having five separate zones that can be independently controlled.

The new system is totally automatic and identifies problems in the system easily (e.g. nozzles not working).

Overall the orchard is now using approximately 60% less water with additional power savings. The frost protection system has seen more drastic savings; a comparison of frost protection usage over similar climatic conditions from the 29-31 May 2018 and 16-18 April 2019 showed 150 cubic metres over 12 hours and 15 cubic metres over 7.5 hours respectively – an 84% reduction in water use under the same frost conditions. The capital cost for optimizing the system was minimal compared to the benefits Chris is now seeing on orchard. The reduction in water being pumped into the orchard has had a significant impact on tree health and fruit quality as only four trees are now considered to be in ‘poor’ health.

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Fruit staining

In October 2019, Jerome Hardy along with Sarah Sorensen from NZ Avocado revisited an orchard on Otaika Valley Road following the implementation of an annual orchard management recovery plan to mitigate the effects of what is termed fruit staining – a disorder largely observed in the Whangarei area. The visit was to gain an understanding of the details and scope of the orchard management plan and observe and report the effects of the programme on reducing fruit staining on fruit. To read the full case study of how the grower turned their orchard around click here .

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