Impact of Different Macadamia Husk Compost (MHC) Application Rates on Leaf Nutrient Content, Tree Yield, and Nut Quality in a Macadamia Nut Orchard

Compost derived from macadamia husks provides a sustainable alternative for improving soil fertility, nutrient uptake, and crop productivity. This study evaluated the effects of different macadamia husk compost (MHC) application rates on nut yield, nut quality, and leaf nutrient concentration in macadamia trees. Compost application significantly (p < 0.05) increased leaf potassium (K), magnesium (Mg), and zinc (Zn) concentrations, with the highest values recorded at 12 t ha−1. Other nutrients (N, P, Ca, Cu, Mn, Fe, and B) were not significantly affected. Nut yield increased with compost application, with the highest yield observed at 12 t ha−1 (63.10 kg tree−1), followed by 8 t ha−1, 4 t ha−1, and the control. Similarly, nut-in-shell yield improved with increasing compost rates. Compost application enhanced key nut quality parameters, including sound kernel recovery, total kernel recovery, and first grade nuts, while maintaining insect damage and immature nuts within acceptable industry standards. Overall, nut quality improved in 2022 compared to 2021. These findings demonstrate that macadamia husk compost is an effective organic amendment for improving yield, nut quality, and selected leaf nutrient concentrations, contributing to sustainable macadamia production.