Stacking soil health practices is necessary to enhance soil ecosystem multifunctionality of semi-arid almond agroecosystems

Identifying strategies to rebuild healthy, living soil ecosystems is critical to alleviate widespread soil degradation and enhance the multitude of soil functions fundamental to sustainability, resilience, and agroecological transitions. This is particularly true in California's almond agroecosystems where a combination of semi-arid climates and historical emphasis on aboveground production components has left soils degraded and the most effective strategies to build healthy soil remain unclear. We used a regionally specific survey of commercial orchards to evaluate relationships between adoption of soil health building practices, soil ecosystem functional outcomes, and soil ecosystem multifunctionality. Orchards with applications of single or few principles without orchard redesigns didn't differentiate from bare soils and had the lowest multifunctionally score across the Alley and Tree management zones. In contrast, orchards with stacked application of multiple soil health building practices, such as diverse vegetative understories with animal grazing had the highest soil organic carbon, total nitrogen, soil protein, available P, soil respiration, and robust and diverse soil nematode communities, which resulted in the highest soil multifunctionality score. Results from this study indicate that a diverse and stacked application of soil health principles is the most effective strategy to enhance multiple soil ecosystem functions in perennial semi-arid agroecosystems. It also demonstrates the potential for this approach to uncover the nuanced outcomes of soil health building principles in growers' orchards. As research continues to show the context-specific nature of management's relationships to soil outcomes, this study offers new insights into regional soil health potential and the efficacy of adopting several practices to promote synergistic soil ecosystem functionality in in irrigated semi-arid agroecosystems. • Stacking soil health practices is necessary to enhance soil ecosystem multifunctionality in semi-arid irrigated almond orchards. • Minimal application of soil health principles didn't impact soil ecosystems. • Animal integration is key to building soil carbon and regulating fertility.