Fitting soil extracellular enzyme activity into the complex network of abiotic and biotic soil properties often associated with soil health

Megan G Taggart^1*Douglas S Baah²Sophie Allen¹Barry MG O'Hagan³Joerg Arnscheidt²Philip Jordan²Aliyu I Dabai⁴JR Rao⁴Nigel G Ternan¹

• ¹Nutrition Innovation Centre for Food and Health (NICHE), School of Biomedical Sciences, Ulster University, Coleraine, United Kingdom
• ²School of Geography and Environmental Sciences, Ulster University, Coleraine, United Kingdom
• ³Centre for Genomic Research, School of Biomedical Sciences, Ulster University, Coleraine, United Kingdom
• ⁴Soils Health Research Group, Soil Molecular & Environmental Microbiology Unit, Agri-Environment Branch, Environment and Marine Sciences Division, AFBI, Belfast, United Kingdom

In this mini review we examine how soil extracellular enzymes play a key role in nutrient cycling, but stress that their activity alone does not fully represent ecosystem processes. We emphasise the need for more contextual environmental data-such as pH, temperature, moisture and nutrient availability-for accurate interpretation of the significance of enzyme activity in carbon and nutrient (N, P) cycling in soil ecosystems. The importance of enzymes within the soil microbiome determines its inherent capacity to support crop growth and often reflects soil quality and soil health, which are in turn governed by multiple different soil properties. Soil enzymes (e.g., phosphatase, glucosidases, glycosaminidases) activity have been used as key soil health bio indicators for monitoring soil nutrient transformations in overgeneralised statements. Although soil enzymes constitute important attributes that are closely linked to the dynamics of soil nutrient transformation and make nutrients available to plants, we suggest a multi-factor assessment for soil health measurement. We propose that this can give a pulse reading of soil nutrient health at crucial times of soil, land use, and crop management practices but that care is required to incorporate temporal soil and land use properties for correct interpretation.