Developing Management Practices in: “Living Labs” That Result in Healthy Soils for the Future, Contributing to Sustainable Development

Abstract

There is general agreement on the need for sustainable development, but the concept has remained rather vague until seventeen specific goals (SDGs) were approved by the UN Assembly in 2015, including targets and indicators. The EU followed this example by introducing their Green Deal in 2019. Soils play a very important role in realizing these goals by the intended year of 2030 in terms of (amongst other less directly related goals) contributing to food production (SDG2: “zero hunger”), good health and wellbeing (SDG3), water quality (SDG6: “clean water and sanitation”), sustainable production (SDG12: ”sustainable consumption and production”), carbon capture and greenhouse gas emission (SDG13: “climate action”) and soil health and biodiversity preservation (SDG15: “life on land”). Of course, not only soils but many other scientific disciplines contribute to achieving the SDGs, and the EU Mission Board for Soil Health and Food has, therefore, defined soil health in terms of specific soil contributions to interdisciplinary ecosystem services: “soils supporting ecosystem services in line with the SDGs and the Green Deal”. Restricting attention in this paper to soils, the Board has defined six indicators for soil health that allow an integrated assessment of the role of soils, reported in this paper in a slightly modified version: presence of soil pollutants, organic matter content, structure, biodiversity, nutrient content and water regimes. Currently, different indicator systems are being used while soil research is rather fragmented, as future environmental policies are still being discussed. The research and policy arenas face major challenges at this point in time to rise to the occasion by defining clear operational assessment procedures for soil health that will, above all, be accepted and internalized by land users, of which farmers manage the largest land area. Only then can implementation be realized in practice. An effort is needed to test the vast body of existing techniques and expertise and focus new research on gaps that appear. This is discussed in detail for the six indicators distinguished, and particular attention is paid to defining threshold values, separating the “good” from the “not yet good enough”. New ways have to be explored to achieve real and productive interactions between scientists and stakeholders, including farmers. The establishment of Living Labs aimed at realizing successful Lighthouses is, therefore, seen as an effective way for scientists to work with farmers in developing innovative management schemes, including the role of soils, expressed in terms of indicators and thresholds for soil health. Such procedures should be the basis for future rules and regulations, where a “one-out, all-out” principle can be used for the various indicators to avoid the current complex discussions about deriving a single, overall soil health indicator.

1. Introduction

This special issue of Land on “Soils of the Future” focuses on a future where healthy soils can continue to contribute significantly to the successful management of forests, grassland and cropland, a list that can also include city greens and various recreational facilities. There is reason for concern. In Europe, for instance, 60–70% of soils are unhealthy, as they are degraded by various processes, such as pollution by heavy metals and various organic chemicals, compaction, depletion of organic matter, loss of biological activity and erosion [1]. How then to create innovative management procedures that can not only remediate existing but also avoid future soil degradation?

The central concept of soil health was proposed not only to assess actual soil conditions by formulating operational indicators and thresholds but also to form a basis for improved management if actual conditions are considered to be inadequate. Thus far, successful soil health programs have been established in the USA by Cornell University [2], the National Soil Health Institute (www.soilhealthinstitute.org, accessed on 20 November 2022) [3] and the US Department of Agriculture [4]. The 2021–2027 Research and Innovation program of the European Union (“Horizon Europe”) defined five Missions, with one among them on “Soil Health and Food”, (recently renamed as “A Soil Deal for Europe”) that receives substantial funding [1,5,6]. Soil health is, therefore, now also on the European policy and research agenda, but effective, operational measurement and research procedures, all to be realized in ecosystem and social contexts, still need to be largely developed, as explored in the next section. Environmental issues are becoming ever more alarming, and the objective of this opinion paper is to explore contributions that the soil science discipline can make in the near future by embracing the soil health concept, thereby contributing to the development of innovative management practices that can alleviate problems encountered. Our conclusions and recommendations are partly based on a case study discussing operational methodology based on available research data and the need for innovative technology [7].

2. The Soil Health Concept

Recent reviews of the soil health concept have concluded that there is, as yet, no broadly accepted standard protocol with clear indicators and thresholds to determine soil health [8,9]. The Cornell protocol [2] has four physical, four chemical and four biological indicators and defines a graphical procedure to obtain an average value for overall soil health. Initially, it started with, respectively, 17, 15 and 11 indicators, and field research resulted in the reduction. The National Soil Health Institute initially had 19 physical and chemical indicators but recently decided to reduce the number to three: % carbon, C-mineralization and aggregate stability. The Dutch “openbodemindex” (www.openbodemindex.nl (accessed on 15 November 2022)) uses nine, eight and three indicators, respectively. The Mission Board advised three, two and one indicator, respectively (see Section 5.1). The Global Soil Partnership (FAO, Rome, Italy) uses seven, five and one indicator, respectively, for the three categories [8]. A focus on soil functions is suggested, and rather than develop a single universal indicator dataset for biodiversity, different sets for different soil functions are suggested [8] (see Section 5.5). Therefore, even though some indicators appear in various systems [10], there is still much variety, and it is not clear if, how, when and where a common practice will be defined, if at all, let alone be agreed upon.

Lack of an agreed procedure to measure soil health after decades of study is problematic as it, obviously, does not allow a systematic, universally valid assessment of soil health. Without this possibility, the entire soil health operation lacks focus. How then to proceed?

An important basic question has been raised [11,12]: “what do we want to achieve when proposing the application of the soil health concept?” We suggest two key goals:

• The demonstration of the contribution of soils expressed in terms of soil health to achieve the UN Sustainable Development Goals by supporting key ecosystem services. The SDGs, which have not been mentioned in recent soil health reviews, allow connection with the international science and policy arenas and provide a much needed “point-at-the-horizon”. Exclusive focus on soil functions restricts attention to the soil bubble.
• The co-creation of operational methods to measure soil health and be actively and genuinely involved with land users in Living Labs to develop and achieve adoption of successful management procedures resulting in ecosystem services that meet their thresholds while showing that healthy soils make crucial contributions.

Both issues are discussed in more detail in the following section.

3. Key Issues When Implementing the Soil Health Concept

Considering the above two key goals, we discuss seven aspects:

• Actions should be seen in the overall context of sustainable development since 2015 and should be defined in terms of the goals, targets and indicators of the seventeen United Nations Sustainable Development Goals (SDGs) (https://sdgs.un.org (accessed on 10 November 2022). This allows a structural connection between the research and policy arenas. For agriculture, this implies multifunctional land use, where soils contribute to food production (SDG2: “zero hunger”), good health and wellbeing (SDG3), water quality (SDG6: “clean water and sanitation”), energy conservation (SDG7: “affordable and clean energy”), sustainable production (SDG12: “sustainable consumption and production”), carbon capture and restricting greenhouse gas emission (SDG13: “climate action”) and soil health and biodiversity preservation (SDG15: “life on land”). These six items represent environmental elements of the SDGs, which represent only part of the SDG story, as economic and social aspects need attention as well. Even though economic and social issues are beyond the direct scope of the soil science discipline, they should not be ignored when dealing with environmental issues, as they are essential for the current agricultural transition process. In the overall SDG context, soil functions contribute to ecosystem services that, in turn, contribute to the SDGs [13,14]. Attention in the following is restricted to agriculture, where farmers manage the largest land area, but the soil health concept is, of course, also highly relevant for other forms of land use, as mentioned in the introduction.
• If farmers qualify, they can receive subsidies for their entire production systems, where not only environmental goals are considered in the SDG context (defined in terms of “ecosystem services” provided by the ecosystem), but also economic and social requirements that are of prime importance in real life. Subsidies within the European common market are provided by common agricultural policies, and current plans already partly focus on the provision of ecosystem services. These subsidies are needed because market prices do not reflect the contributions of agriculture to general prosperity that are now well-articulated by the SDGs. When the thresholds for various ecosystem services are met, a positive environmental contribution is made toward reaching the SDGs involved. Then, a Living Lab can become a Lighthouse (Figure 1). A case study [7] assessed ecosystem services for a farm on light, calcareous clay soil in the Netherlands. Attention in this paper is focused on the health of this particular soil.

3.

Even though all farmers acknowledge the importance of soils in their operations, soils are not the only game in town, a message that soil scientists should internalize. Ecosystem services are defined by interdisciplinary research, whereby soils are an important part of the soil–water–atmosphere–plant system. Demonstrating this clearly is the best form of soil promotion [16]. Some current definitions of soil health (e.g., “the ability of soil to sustain the productivity, diversity and environmental services of terrestrial ecosystems” [17]) suggest separate and single roles of soils, implicitly ignoring the contributions of other disciplines. The definition proposed by the Mission Board of Soil Health and Food avoids this, stating “the continued capacity of soil to support ecosystem services in line with the SDGs and the Green Deal” [1,6]. Of course, soils contribute to all the SDGs considered, and soil contributions are, therefore, particularly important, also reflecting the fact that soils make major contributions to the other four EU missions: adapting to climate change, combatting cancer, restoring oceans and waters and establishing climate-neutral and smart cities. All goals, including those of the soil mission, are to be reached by 2030. Overall, we should realize that the SDG initiative represents, therefore, only one step of what should be continuing development. Still, it provides a focus for the next eight years. This paper also intends to present a contribution to an ongoing, as yet unfinished process that is partly based on a specific case study [7].

4.

Improving soil health, as required by the Soil Deal for Europe, is the result of the implementation of appropriate management measures. Even when developed on government-funded experimental farms, there is no guarantee that farmers will adopt such measures if they do not fit their particular farming styles. The active participation and commitment of farmers when developing innovative management procedures is, therefore, crucial to obtain success, and this requires open-minded attitudes of researchers and other stakeholders in the context of joint learning. At stake is the transformation of traditional farming culture into the vital element of a sustainable world. The European Commission requires, therefore, that research on innovative management measures should be performed in so-called “Living Labs”, where researchers and farmers work closely together. The Soil Deal for Europe requires the establishment of at least 100 Living Labs in various EU countries by 2030 [6]. As this will probably require international cooperation, a 2030 timeframe is realistic, though still quite ambitious. When the indicators for various ecosystem services are met on a given farm (see Figure 1), a Living Lab can become a Lighthouse, an example for others to follow, as its management is well-described. The “Living Lab–Lighthouse” model can also be applied to soil health, and there are cases where a farm being discussed does meet thresholds for the various soil health indicators but not those for the ecosystem as a whole (the case study in [7]). Then, the farm can still act as a soil Lighthouse.

5.

Again, ecosystem services can only be assessed by interdisciplinary efforts, where disciplines other than soil science often play dominant roles. For instance, plant breeders are now capable of genetically modifying crops, making them less susceptible to drought and diseases. If, for example, they succeed in the future to increase the efficiency of chlorophyl from the current 3% to 6%, the effect on crop production would be spectacular (SDG2). Water quality can be improved by precision agriculture, requiring innovative technical equipment and software that play crucial roles in reducing the leaching of agrochemicals. Without such technical developments, precision agriculture will remain a theoretical concept (SDG6). Solar energy and energy generated by windmills are more attractive as sources for sustainable energy than biomass production, which has other, more attractive destinations (SDG7). Carbon capture in soils can, to a certain and often limited extent, be increased by manuring and growing cover crops, but establishing an innovative, circular composting system based on large volumes of organic city waste could especially have a major impact (SDG13). Biodiversity is highly affected by climate change, and ecologists have a function in defining new temporary equilibria for plant communities in the future to allow meaningful relations with soil conditions (SDG15). The latter introduces the important element of continuous change that should guide the overall debate. Simply trying to maintain what is and basing indicators on the research of decades ago is inadequate for facing the rapidly changing environmental and societal conditions of the years to come.

6.

A problem when discussing soil health is the rather separate activities of the various subdisciplines of soil, e.g., chemistry, physics, biology and pedology. Only a unified approach can result in a meaningful contribution to ecosystem services (Figure 2). The modeling of the soil–water–plant–atmosphere system is helpful in realizing the necessary interactions among these subdisciplines. Many well-tested models are available for this form of system analysis [18,19,20,21,22,23,24]. Models are particularly valuable to characterize the physical–chemical soil conditions that are important for particular groups of soil organisms, offering the possibility to define a proxy for soil biodiversity [25], as discussed in Section 5.5. Ecosystem services contribute directly to environmental aspects of the SDGs, but they are indirectly also relevant for social and economic considerations that have to be considered before final conclusions can be reached regarding whether or not SDGs have been reached (Figure 2). If a given soil is unhealthy, its contribution to ecosystem services should be improved, and economic considerations are likely to play a role in exploring new, innovative forms of management. The “one-out, all-out” principle followed here when defining soil health (see Section 5.1) implies that an unhealthy verdict is associated with a statement as to which indicator (or indicators) did not meet the threshold. Attention and research can then be focused on that particular indicator (or indicators), including economic considerations. However, various scientific disciplines, including soil science, should be prepared for situations in the real world where economic considerations may prevail, even if their indicators do not meet the thresholds.

7.

Soil Health has been studied for many years, and some excellent reviews of the concept have been published [8,9,10]. Thus far, however, there is no unified procedure to assess soil health with indicators and thresholds that can be determined by operational methods under practical conditions considering critical cost and required time aspects. The availability of such data is a crucial success factor for any soil health program. Considering the importance of assessing soil health both now and in future as it contributes to ecosystem services, attention in this paper is focused on a discussion of operational indicators and thresholds for soil health. The focus is on what can already be implemented at this point in time, assessing the roles of existing data and methodologies with reference to a published exploratory case study [7].

4. Soil Health versus Soil Quality

The use of both soil quality and soil health to characterize soil behavior is confusing for outsiders. Suggestions that both terms have the same meaning imply that only one of them should be used. Why have two terms for the same concept? Both terms are important as communication tools [26], and soil health registers well with people, as there is an analogy with human health. A medical doctor uses health indicators that determine whether or not a given patient is healthy at a given moment. This compares directly with the soil health indicators applied at a particular moment to an individual soil, a “pedon”, a living body. Even one negative indicator leads to a non-healthy diagnosis in the “one-out, all-out” system. However, human health also has a broader meaning when distinguishing health statistics for groups of people (“cohorts”), for example, 18–25 or 60+ age groups, immigrants, levels of education, etc. Such cohorts can be compared with soil types, or the genoform, defined by soil classification based on soil genesis. Within a given soil type presented as spatial patterns on soil maps, soil health variation is likely to occur as a result of different forms of management. This has been demonstrated for different Italian soil types in terms of the negative effects of compaction and erosion and the positive effects when increasing organic matter content [21,22,23,27]. Such results of management are called phenoforms and occur within a given genoform [28,29]. The effects of climate change have also been explored and, again, show characteristic differences in the reactions of different soil types. The importance of this is shown by the fact that each soil type has a characteristic range of indicator values as a function of management and climate change, as expressed by characteristic phenoforms of that soil type. As we do not support one particular overall value for soil health that somehow integrates the five indicators (a soil is healthy or it is not), we define soil quality by the ranges of the separate indicators found within a certain soil type (genoform). This can be compared with the characteristic variations in health statistics within a certain cohort of people and between cohorts. We feel that both soil health and soil quality can, in the above context, be effectively used for communication purposes.

5. Soil Health Indicators

5.1. Proposed Indicators and Procedures

A list of indicators was proposed by the Soil Mission [1]: soil pollutants, % carbon, soil structure, soil biodiversity, soil nutrients and soil water regimes. They reflect important key conditions for the rooting of plants, which provides a clear focus. The last item was added to the original list, while vegetative cover, landscape heterogeneity and forest cover were omitted, as they describe land use and would not allow the “one-out, all-out” approach to be discussed later. Operational methods are discussed in the following sections, emphasizing the need for rapid, relatively inexpensive methods that can be used in the field. A key element is the definition of threshold values, separating the “good” from the “not yet good enough”. This differs regionally and also by soil type and requires additional field research. When an indicator is “not yet good enough”, alternative forms of management have to be explored, either derived from Living Labs on similar soils, site research or the literature. Research can then be focused specifically on a particular indicator. When discussing the various indicators and thresholds, reference is made to an exploratory case study on a Living Lab, an arable farm on light, calcareous clay soil in the Netherlands. Data are shown in

Table 1. Soil health indicators for the Living Lab described in the text. Conclusion: this soil was healthy and offered a positive entry point for SDG15 in terms of the lack of soil degradation.

Soil Health Indicator	Actual Value	Threshold	Result
Soil pollution: EU and local reg.	below thresholds	in env. laws	positive
Soil structure: bulk density	1.35 g/cm3, sd 0.08	1.55 g/cm3
Penetrometer res.	0.67 MPa, sd 0.31	5 MPa	positive
Organic matter content	2.9%, sd 0.32	2.0%	positive
Soil biodiversity	% org matter as proxy	not yet defined	positive
Soil fertility	regime based on soil testing		positive
Soil moisture regime	well-drained	mod. well-drained	positive

[7].

Efforts to define a single value for soil health at a given time by somehow combining and balancing separate indicators have been questioned [8,9]. We agree that, because various indicators have quite different backgrounds, mixing them by an arbitrary procedure leads to a loss of focus on what can and should be implemented to improve overall soil health.

These problems do not occur when the “one-out, all-out” principle is followed. A soil is not healthy when one or more of the indicator thresholds is not met. A soil is healthy or it is not (note that the same procedure is followed for ecosystem services [7]). Making formal distinctions when only a few indicators are not met (“the soil is not quite healthy, but…”) is not recommended, as it clouds discussions. It is interesting to note, finally, that proposals to have a single indicator have only been made for soils and not for ecosystem services where this would, of course, also be meaningless.

5.2. Soil Pollution

The occurrence of soil pollutants in terms of heavy metals and various organic compounds has been well-documented and is the object of current environmental legislation in many countries. Reference is made to easily accessible national and EU websites with further details. The field is highly dynamic, as new pollutants are frequently identified (e.g., PFAS). The soil pollution issue is paramount in industrial sites and on some forms of reclaimed land. Of particular concern for agriculture are biocides and their remnants in soil. Alarming environmental and human health risks were recently discussed [30]. When assessing soil pollution in the context of soil health determination, lists for every Living Lab and all possible pollutants, as well as demanding confirmation of whether or not thresholds for each are exceeded, are not realistic, as the large majority of soils are not polluted. When, however, there is reasonable doubt about conditions at a given Living Lab, a standard analysis package should be applied by a certified agency, and the results of that analysis determine whether or not the soils being studied pass soil pollution thresholds. The soil in the case study was not polluted (Table 1).

5.3. Soil Carbon Content

An up-to-date and well-documented review was published on methods for measuring soil carbon contents and assessing the potential of soil carbon sequestration for atmospheric greenhouse gas removal [31] (related to SDG13). However, soil carbon is also important for the moisture supply capacity of soils, as well as for physical aspects of soil management, such as trafficability and workability (all related to SDG2). These three soil functions (moisture supply capacity, trafficability and workability) can be improved as water-holding capacity and soil strength increase with increasing organic matter content [32]. Carbon content is traditionally measured in a laboratory, but new sensing techniques are now available that allow instant data collection at a large number of locations. This is very attractive, and application of these modern techniques is highly recommended [33,34,35,36,37].

Defining appropriate thresholds presents a particular challenge, as they are different for different soils and climate zones. In this context, the organic matter contents of fields at 40 farms on majorly clay and sandy soils in the Netherlands have been determined [38,39]. Organic matter contents of the surface soils could be related to actual and past land use with a surprisingly high correlation coefficient of 0.75. Contents varied between 1.7 and 5% for the clay soils and between 4.0 and 6.8% for the sandy soils, reflecting traditional arable management and permanent grassland, respectively. Intermediate values of 3.3% were obtained for organic arable farming on clay soil and 5.5% for reseeded grassland on sandy soil. These values could act as thresholds for these two particular major soil types. Different soil types have characteristically different ranges of organic matter contents as a function of management, and thresholds should, therefore, be defined by (major) soil type. These 40 farms acted as Living Labs, even though that name had not yet been coined. Organic matter contents of different soils as a function of management were also reported in a large Swiss field study [40]. This type of project is needed, contributing to broad, management-related and process-oriented field studies on soil organic matter. The soil in the case study had an average organic matter content of 2.9% with a threshold of 2.0%, resulting in a positive judgement (Table 1). The threshold was estimated by judging the organic matter content as a function of management in arable land on the same soil type and is still empirical.

5.4. Soil Structure

Soil structure descriptions are part of soil survey reports [41]. They note the spatial distributions of soil particles and aggregates, as well as voids. Such qualitative assessments are an important start for soil structure evaluation but need quantitative support. Three methods stand out at this time: (1). Bulk density is widely determined by sampling small cores, followed by measurement in a laboratory. Aside from being quite time consuming, variability may be very high in structured soils when larger, undisturbed samples are needed to be representative. High standard deviation among multiple small samples makes it difficult to assess whether or not thresholds are met. (2) Penetrometer resistance can be measured in the field, allowing rapid measurements at many locations in a short time. (3) Aggregate stability is an indirect measure for soil structure but involves field sampling, is time consuming in a laboratory setting and has highly variable results, partly due to sample pre-treatment. For details on all these methods, see [42]. Thresholds for bulk density and penetrometer resistance were met in the soil in the case study (Table 1) and were derived by observing rooting patterns in the field in this particular type of soil as a function of different forms of management. New techniques are currently being developed, allowing the direct measurement of soil densities in the field with sensing methods [42,43]. Such techniques are most welcome because they can cover a larger volume of soils and, once equipment is available, are rapid and relatively inexpensive.

5.5. Soil Biodiversity

Currently, the National Soil Health Institute in the US uses two biological indicators: carbon content and carbon mineralization. The Cornell scheme applies organic matter, the ACE soil protein index, soil respiration and active carbon. The Dutch openbodemindex (translated) includes pest resistance, biological activity and earthworm density. In our exploratory Living Lab case study, we concluded that, so far, no clear indicators, let alone corresponding thresholds, were available for soil biodiversity [7]. The organic matter content was, therefore, used as a proxy value, with a threshold corresponding with that for carbon content. The judgement was positive (Table 1). Better procedures are needed.

When developing new approaches to assess soil biodiversity, an important proposal was made to use different sets of “actors” for four soil functions [8] (thus deviating from the seven soil functions defined by the EU [44]). The proposed BIOSIS system to assess soil biodiversity [45] contained 191 biological-actor-level methods and 98 process-level methods. Time will tell if this complex system can provide operational data to assess soil health. Soil biodiversity must be assessed at a Living Lab level (context 3 of [8]: “soil quality monitoring over time”). Comparing results for different Living Labs on the same type of soil is next aimed at defining optimal sustainable land management by satisfying various ecosystem service thresholds (not only the one for biodiversity). If this is achieved, a Lighthouse can be established. In line with this, the correct recommendation was made that “assessment of soil properties and recommended management actions will likely need to be site specific” [25]. Context 2 of [8] (“optimizing sustainable land management”) appears to be rather focused on soil biology but relates to comparing results of different Living Labs, as mentioned above, where other ecosystem services are also important. Context 1 [8] (“mechanistic understanding of multifunctionality”) is a plea for yet more research.

In contrast to the other soil health indicators, the conclusion must be that the verdict is still undecided for soil biodiversity. Following [25], which conclude that an “abundance of soil biota may simply be the consequence of improved conditions for microbial activity such as rewetting of soil or inputs of organic matter”, perhaps it is possible to define soil physical–chemical conditions that are favorable for certain groups of micro-organisms, thus allowing those conditions to act as a valid soil biodiversity proxy.

5.6. Soil Nutrients

In most countries, soil fertilization practices have been guided for many years by recommendations made by specialized laboratories, including sampling procedures. Such recommendations vary for different types of soil and crops to be grown, and indicators and thresholds differ in different countries. Defining a long general indicator set for soil nutrients listing all the macro- and microelements involved in plant production to be determined at a specified moment during the growing cycle would not be meaningful as part of what should be an internationally acceptable soil health indicator set. We pragmatically suggest following the national schemes now in use. Why repeat a soil nutrient analysis as part of soil health assessment when this has already been conducted by national experts? Soil fertility testing is part of modern farm management. When a professional fertilization recommendation has been provided for a given Living Lab and followed (as in [7] and shown Table 1), we assume that the soil nutrient indicator is positive. The modern development of precision fertilization departs, however, from traditional recommendations for one fertilization rate, transforming this into fine-tuned applications during the growing season as a function of plant demand. This saves fertilizer and its associated costs and avoids leaching of excessive fertilizer to groundwater [46]. We see this as an important future development that is focused on particular locations, considering specific demands by different crops by applying modern information technology (see also point 5 in Section 3).

5.7. Soil Water Regimes

A well-aerated soil with adequate amounts of moisture and nutrients where all parts can be reached by plant roots is ideal not only for plant growth, but also for biological activity. Soil survey procedures [41] define soil moisture regimes in descriptive terms, such as well-drained, poorly drained, etc., observing morphological soil features, such as mottling patterns of iron. More quantitative expressions can be obtained by modeling, as mentioned in point 6 of Section 3. This also allows the exploration of effects of climate change. When soils are either too wet or too dry, the indicator for soil water regimes must be negative. Soils in the case study were well-drained, allowing a positive judgement (Table 1). A moderately well-drained soil does not qualify because this indicates significant periods of wetness, inhibiting root development. Thresholds vary by soil type and climate region and can, as a follow-up of soil survey classification, be based on calculated moisture supply capacities. The often used “available water” concept, defining water held between field capacity and wilting point, is a static value that cannot express varying conditions in the field, which are needed to define a valid indicator for the soil water regime. Only modeling (or monitoring of actual conditions) can produce relevant results. Basic data for modeling can be derived from measurements or pedotransfer functions relating elementary soil data (e.g., texture, bulk density and % C) to parameters needed for simulation, such as moisture retention and hydraulic conductivity [47,48].

5.8. Overall Soil Health

All indicator thresholds were met in the Living Lab study, indicating that soil degradation, which is part of SDG15, did not occur. Soil management, as documented in the case study [7], can now be communicated to other farmers operating on the same type of soil as inspirational information. This also applies to the citizen and policy arenas as an example of favorable soil management.

6. Discussion

The effects of climate change are becoming ever more evident all over the world. Less directly visible but just as important are declines in water quality and soil health. Looking toward the future, the focus of this special issue is also more relevant than ever for soil science. Soil research during the last decades has produced large amounts of data and insights for soil processes that are crucial to facing future challenges. Available data can be used to assess current soil conditions, but important data are still missing. However, proxies can often be found. Research should, therefore, certainly be focused on knowledge gaps, but researchers should resist the common tendency to not act now and wait: “the better is the enemy of the good” [49]. In this context, an exploratory attempt using available knowledge to define ecosystem services and soil health was conducted on a Dutch farm [7]. Much current research still has, however, subdisciplinary characteristics, focusing on soil chemistry, physics, biology and pedology (see Figure 2). More integration emphasizing soil contributions to a system analyses of the soil–water–atmosphere–plant system is needed as part of an effort to support a number of crucial ecosystem services. Considering the SDGs, as well as their targets and indicators, can, as an inviting “point-at-the-horizon”, focus activities of the soil science profession, connecting them with the global research and policy arenas. In addition, climate change has a major effect on sustainable development when facing the future, and assessing the effects of climate change has become ever more important when characterizing soil processes [21,22,23].

The soil health concept fits into this scheme, as it can be defined as “the continued capacity of soils to support ecosystem services in line with the SDGs and the EU Green Deal”. Thus far, there is no agreement on the required set of indicators for soil health. Perhaps PEDOMETRICS, the most active working group of the International Union of Soil Sciences, can address this issue, the more so since they defined “ten challenges for the future of PEDOMETRICS” [50], of which challenge 10 (quantify soil contributions to ecosystem services with a framework enabling local and regional soil management) addresses the indicator issue directly. Additionally, challenge 4 (can we measure soil properties more efficiently?) is quite relevant because operational measurement methods are needed that are relatively inexpensive and can produce a large number of, preferably, instantly available data. When discussing indicators, we therefore emphasize the importance of introducing various types of sensing techniques.

Contributions to ecosystem services can, no doubt, be well-defined by scientific analyses, but if they are not implemented in practice, they remain an isolated bubble in the academic domain. The establishment of Living Labs, as proposed by the European Commission, can help to close the current gap between society and the science and policy arenas by creating awareness of the various dimensions and challenges of sustainable development that, in the end, affect all individual citizens. The Mission Board of Soil Health and Food [1] published a manifest in their report that articulated this broad, society-oriented context.

Land users, of which farmers use the largest area of land, have practical experience and considerations that should be reflected in whatever is incorporated into environmental rules and regulations. For example, a top-down theoretical concept of multifunctional land use may not appeal to farmers, as many practical aspects of running a farm seem to be ignored [51]. Good examples of “harvesting knowledge” as a basis for continuing research were presented [52], and this type of study is very much needed. This does not imply that input from farmers should be uncritically embraced. They and other land users are open to debate, but only when their input is taken seriously, and above all, they want clarity. At this point in time, there is much criticism about unclear and often mutually conflicting environmental regulations that do not reflect practical expertise and limitations. The proposed procedure that defines indicators and thresholds for ecosystem services could provide this type of clarity. It should be noted that the common agricultural policy of the European Union intends to pay part of their support subsidies on the basis of provided ecosystem services. This refers to an entire farm operation. The soil science profession can demonstrate soil contributions to these ecosystem services, and healthy soil defined by specific indicators and thresholds can make the highest contributions. Showing this is the best form of soil promotion.

Finally, when looking at the future, soil health is a valuable concept, but it is limited in its contributions to the overall environment. Sustainable development also has important economic and social dimensions that are reflected in the broader soil security concept, as proposed by Australian scientists [53]. This is defined by the five Cs: soil condition (soil health), soil capability (the range of soil health values for a given soil as a function of management equal to the proposed definition of soil quality), soil capital (the ecosystem services contribution by a given soil type compared with other soils), connectivity (with other scientific disciplines and with the citizen arena) and codification (representation in environmental laws and regulations). Soil security, or “how to secure our soils” is a most suitable phrase for the soil science profession to face the future in a societal context.

In fact, the Soil Health program in the US (www.soilhealthinsitute.org (accessed on 20 November 2022)) already provides an example of a broader approach reaching beyond soil science and other environmental disciplines. On-farm research at many arable farms focused on soil health, as well as including a strong economic component, has shown that reduced tillage and the incorporation of cover crops, representing the so-called regenerative form of agriculture, not only increase the yields, but also the net incomes of farmers as costs decrease. Cynics may say that the beneficial effects of these two management measures have been known for decades, but this would be unfair because now the unique contribution of soil health has been well-documented for the first time. Because of these results, major industrial partners and interest groups have joined the soil health effort of the Soil Health Institute, a convincing and inspiring sign of success that needs to be followed elsewhere. Still, researchers report that, despite convincing environmental and economic evidence, many farmers are still reluctant to adopt regenerative management systems. This indicates that the social dimension of sustainable development still needs more attention and is yet another indication that soil health is only one factor in a highly complex societal system.

7. Conclusions

• “Soils for the future” should be considered in the context of sustainable development, for which seventeen goals were articulated by the United Nations in 2015. Healthy soils make the highest soil contributions to ecosystem services in line with these goals, and a number of indicators with threshold values for soil health were discussed in this paper, emphasizing the need for the application of relatively simple operational methodology at the field level. Much can already be achieved with currently available data and expertise.
• Healthy soils can be created and maintained by appropriate land management. The European Commission advocates the joint work of land users and scientists in so-called “Living Labs” that, when successful in terms of satisfying a number of required ecosystem services, can act as inspiring “Lighthouses” for other land users and stakeholders, as well as in the policy arena. We strongly support this because success can only be obtained when the bottom-up expertise and interests of land users, of which farmers occupy the largest area of land, are mobilized and applied in a truly transdisciplinary approach. Creating international sets of Living Labs is time consuming, and the SDG deadline of 2030 also provides a realistic deadline for the Living Lab experiment.
• Satisfying the requirements of ecosystem services requires an interdisciplinary approach in which separate scientific disciplines work together. Soil science cannot complete the job by itself. In this context, modeling of the soil–water–atmosphere–plant system can provide important information, as well as exploring effects of climate change.
• Climate change is already strongly changing environmental conditions, and when defining future soil management methods, indicators and thresholds for ecosystem services and soil health, a dynamic, forward-looking approach is needed. Simply trying to conserve what is there right now and applying data obtained decades ago are likely to fall short of what is now urgently needed right now.