Soils perform a multitude of functions, and soil quality assessment is most useful when explicitly targeting specific soil functions or soil threats . There is no universal indicator of soil quality, rather soil quality is best assessed by a combination of indicators tackling soil physical, chemical and biological properties. Importantly, soil quality assessment needs to provide a clear interpretation of indicator values, and optimum values are site-specific, depending on pedo-climatic conditions as well as land use.

In iSQAPER, the most commonly used soil quality indicators were identified (Gongiorno et al 2019). To support better assessment of soil quality, both laboratory and visual indicators were tested in long-term field experiments as well as on-farm (Alaoui et al. 2020).  In addition to well-established indicators, the iSQAPER project assessed the relevance of novel indicators including labile carbon and soil biological indicators with particular attention to responsiveness to changes (Bongiorno 2020).

Developing more responsive indicators – Understanding Change in Soil Quality and Soil Carbon Associated with Land Management - Some of these novel indicators can help to monitor soil quality in a more responsive way than has been possible until present, with indicators that can reliably demonstrate changes over shorter time periods than has been possible until now. An important outcome was that labile carbon is not only sensitive to soil management, but also closely related to various soil processes and ecosystem functions, such as nutrient cycling via microbial activity, erosion control via soil aggregation, disease regulation via soil suppressiveness, and climate regulation via carbon sequestration (Bongiorno et al. 2019a, Bongiorno et al 2019b). The determination of labile C as permanganate oxidizable carbon (POXC) is relatively cheap, fast and easy, and a much more informative alternative over the short term when compared to the traditional total organic carbon (TOC) indicator. When defined by standardized protocols, the novel indicator permanganate oxidizable carbon (POXC) can therefore be recommended to be included in soil quality assessment schemes (Bongiorno 2020).

Soil Assessment can start relatively simply “in field”, offering valuable real-time insights. Visual Soil Assessment (VSA) combined with simple in-field assessment techniques have been demonstrated under iSQAPER to provide a reliable basis for the on-going evaluation of key soil quality parameters at the farm level (Alaoui et al. 2020). On-farm soil assessments are a useful first step in understanding soil quality in situ helping to review impacts of management changes, and critically can provide useful information to a farmer. This can be used to support the selection of the most promising agricultural management practices for enhancing soil quality across European farms.

Under iSQAPER a manual has been developed (Bongiorno et al. 2019) to determine how to robustly assess the impact of agricultural management practices on soil quality using VSA. The manual can be used as a consistent tool to evaluate soil quality in a standardised and accessible way. It can be used in future to assess soil quality across a wide range of soils and climatic conditions.

One of the central initiatives of iSQAPER has been the development of the mobile phone app, SQAPP (the soil quality assessment app). The SQAPP provides a context-specific score for soil quality and soil threats for a specific locality, enabling users to compare the quality of their soil to the quality in other locations. Most importantly it provides recommendations for the user about the best location-specific management practices to improve the quality of the soil.

This app represents an important breakthrough, providing the user with free access to the best available global soil information, anywhere in the world. The SQAPP provides free and easy access to global soil and landscape data. It provides site-specific interpretation of widely used soil quality indicators, assesses the local threats to soil quality and gives recommendations for management practices that would improve it (»SQAPP guide for policy makers). App users can either use embedded data or add their own data (ideally based on the indicator set and ‘in field’ assessment methods set out in elements 1 and 2) to the database to receive tailored recommendations.

SQAPP is a useful tool for a wide variety of user groups including farmers, agri-advisors, researchers and policy makers, all of whom have been involved in its development and evaluation. It can already be used as a decision support tool for land managers and for research purposes. It could be used to help inform local policy and decision makers about relevant initiatives. The app is very easy to use, and gives the user instant data to benchmark the soil quality in their field of interest to other locations having similar combinations of soil and climate conditions.

Moreover, with further development, SQAPP could evolve into a tool for self-reporting of soil quality data and land management data, filling the earlier-mentioned data gap on management in relation to soil data. This could potentially be a useful monitoring tool applicable in a number of policy areas at Member State and European level.

A great deal of soil quality monitoring is done, but there is a need for this data to be more systematically linked to Agricultural Management Practices (AMPs). Continuous information on AMPs is needed as well as widely available baseline information on soil quality for best monitoring across the EU. An urgent effort is needed to provide more systematic data and monitoring on the link between AMPs and soil quality. Such monitoring should be integrated into standard on-farm reporting requirements.

Results from long-term experiments and farm surveys revealed that AMPs such as minimum soil disturbance, organic agriculture and crop rotation positively affect soil quality, but with trade-offs between different ecosystem services. For example, reduced tillage and organic agriculture typically improve soil organic matter content, soil physical stability and soil as a habitat, but with some yield penalties (Bai et al. 2018). Not only the quantity, but also the quality of soil organic matter (SOM) is central to the multi-functionality of soils. Diverse crops and green manures, organic amendments of different recalcitrance (manure, compost, crop residues, plant mulches) impact quality of soil organic matter. It is important to continually assess the effects of different combinations of AMPs in research and farm settings through field trials.

iSQAPER has identified the most promising AMPs and their combinations that improve soil quality (Alaoui et al. 2020). Combinations of two or three AMPs showed greater positive impacts on soil quality than using single applications of AMPs. More specifically, AMP – soil organic matter relationships show the potential benefit of using combinations of cover crop treatments and no-till or minimum-till to preserve or even enhance organic matter in surface soil layers. Cluster analysis showed that the most promising combinations of AMPs having a positive impact on soil quality are composed of crop rotation, mulching and minimum-till. Organic-matter amendments and organic farming were also identified as important tools to fight threats to soil quality (Bai et al. 2018)

Regional modelling of future land use scenarios shows that the expected (‘business as usual’) scenario is not enough to make significant contributions towards improving the soil environmental footprint. However, a scenario modelling a situation in which policy efforts are focused on improving AMPs in areas where soil threats are more active and soil quality indicators are poorer delivers important benefits in key challenging areas, where the effects greatly improve the soil environmental footprint (Garrote et al. 2019). Thus, in a situation of insufficient resources, targeting efforts on these areas could make significant overall improvements in soil environmental footprint. However, the effects of an intensification of the rate of implementation of beneficial AMPs as a result of public policies yield substantially higher benefits, due to the combined effect of the improvements to ecosystem services modelled, which reinforce each other. The region that shows the greatest improvement of soil environmental footprint in Europe is Mediterranean-South, while the region that shows the least improvement is the Alpine region.

The impacts of AMPs were more notable when implemented in naturally less fertile soils, such as Podzols and Calcisols. In these soils, AMPs presented higher percentages of positive impacts (90-100%), whereas in other soils with intrinsic high fertility, such as Luvisols and Fluvisols, the positive impacts of AMPs were lower (50-60%). This shows that the site-specific context should be taken into account for efficient implementation of the management strategies, and an urgent approach to “hot-spots” of poor soil quality and deterioration would be justified, although a generalised approach would yield better results.