Soil Restoration and Monitoring Guidelines

Soil texture is also an important physical measure, yet as it is not variable under management it proxies more the soil’s capacity than its condition. Therefore, soil texture is discussed in the section “how to monitor”.

Bulk density, expressed in mg/cm³, is a key indicator of soil compaction and overall soil health, influencing water infiltration, root development, and carbon stock estimates (Lee et al., 2009; Panagos et al., 2024; Vogt et al., 2015). It measures the dry mass of soil per unit volume and varies with management practices (Al-Shammary et al., 2018). Sampling methods include direct (core, clod, excavation) and indirect (radiation, regression) approaches; while indirect methods are more accurate, they are also costlier and require specialized skills (Vogt et al., 2015). Consistent fixed-depth sampling - ideally five samples per stand - is recommended to account for variability with depth (Cools & De Vos, 2010). In the SUPERB project, bulk density was measured using the core method at 0-5 cm (100 cm³ Kopecky ring), and an 18 mm auger for 5-15, 15-40, and 40-80 cm layers (FunDivEUROPE, 2011). Samples were oven-dried at 105 °C, weighed, and bulk density was calculated as dry mass divided by sample volume. 

Additionally, aggregate stability is an important indicator for soil health because it is related to erodibility and soil-water dynamics (Rieke et al., 2022). Rieke et al., 2022 evaluated four methods for aggregate stability and concluded that all four methods were viable options. Considering cost-effectiveness, method accessibility, and time efficiency, the slaking test, adapted from the SLAKES smartphone image recognition software, offers a practical and scientifically robust approach for assessing aggregate stability in the field. This method is also preferred by the Soil Health Institute.