Development of a soil health index based on the ecological soil functions for organic carbon stabilization with application to alluvial soils of northeastern Italy

There is a need to assess soil health quantitatively to assist with sustainable soil management in agroecosystems. The objective of this research was to develop a farm- level soil health index (SHI) to help identify the most sustainable management practices including C sequestration and agroecosystem resilience to climate change. For all indexing phases we used the Soil Management Assessment Framework. The SHI was created using a minimum data set (MDS) of physical, chemical and biochemical soil indicators chosen via expert opinion (EO-MDS) (24 indicators) and via the results of PCA (PCA-MDS) (16 indicators). Each observed value was converted into a score (0 to 1) by using site-specific non-linear scoring algorithms. Indicator scores were incorporated into a composite SHI which quantified the ecological performance of 5 soil functions: habitat and biodiversity, water movement and availability, filtering and buffering, nutrient cycling, physical stability and support, and long-term C stabilization. For both MDS evaluations, we assessed agroecosystems managed organically (OS) or conventionally (CS). Results from our study showed that OS had significantly higher (P< 0.05) SHI scores compared to the CS. SHI, with EO-MDS, was more efficient (P=0.028) than the PCA-MDS (P=0.039) when determining the effect of soil management practices on soil health. Non-linear transformation was a useful technique and represented soil ecological functionality effectively. Five out of six soil functions had significantly greater (P< 0.05) ecosystem performance in OS compared to CS, except for water movement and availability. The benefit for OS lead to a greater soil health status, allowing the system to be more resilient to climate change, to efficiently provide nutrients to plants, and to sustain an active soil food web for the long-term stabilization of C. The SHI may help optimize and provide extensive insight into all aspects of soil health which are intricately linked to soil-based ecological functions at the farm level.