Temperature and Precipitation Synergistically Affect Yield, Harvesting Time and Post-Processing Quality of Tropical Macadamia Nuts

In response to climate change challenges and to ensure stable macadamia nut production, this study analyzed empirical data on macadamia nut yield, climate factors, harvesting time, and post-processing quality from 2020 to 2022. Key findings include: (1) During the flowering to fruit growth stage, 2020 had the highest average temperature, followed by 2021, and then 2022. Conversely, 2022 had the highest precipitation, followed by 2021, and then 2020. (2) Lower temperatures and higher precipitation during the flowering to fruit growth stage contributed to a significant increase in macadamia nut yield, which indirectly extended the harvesting time. In 2022, the average yield of the eight macadamia growers was 8.04 t ha⁻¹, significantly higher than the yields of 6.60 t ha⁻¹ and 6.16 t ha⁻¹ in 2021 and 2020, respectively. Furthermore, the average harvesting time for the eight macadamia growers in 2022 was 8.88 days longer than that in 2021, and 12.50 days longer than that in 2020. (3) Temperature and precipitation had a significant impact on the post-processing quality of macadamia nuts. Lower temperature and higher precipitation during the flowering to fruit growth stage significantly increased the proportion of first-grade fruit, as well as the incidence of mildewed and insect-infested fruits. In conclusion, although a lower temperature and higher precipitation can improve macadamia nut yield, they also lead to delayed harvesting and decreased post-processing quality. Given the observed yield sensitivity to temperature and precipitation, targeted water supplementation strategies during peak heat periods emerge as vital. This approach should be integrated with broader climate resilience planning, including the timing of pest control and disease management, to safeguard macadamia nut production against the multifaceted challenges posed by climate change.