Australian Macadamia Orchards Predominantly Function as Carbon Sinks.

The need to develop practices enabling deep and continued reductions in greenhouse gases (GHG) is arguably the greatest challenge facing humanity in the 21st century. Here, we quantify GHG emissions of macadamia enterprises in Australia and then contrast potential abatement realized by practice change. We show that nitrogenous (N) fertilizer accounted for more than half of net farm emissions, followed by fuel and electricity. Soil organic carbon accrual dictated carbon removals and GHG emissions intensity. Many enterprises applied N fertilizer at rates higher than recommended best practices, suggesting that reduced fertilizer quantities may sustainably reduce GHG emissions without impacting yields. We conclude that many macadamia farms are net carbon sinks, which contrasts with other agricultural sectors that are often sources of GHGs. We illustrate how the adoption of bespoke interventions, such as optimization of N fertilizer use, improvement of intrarow ground cover, and avoidance of tillage, can abate enterprise emissions while also improving food security, enterprise prosperity, and environmental stewardship.