Which indicators are most effective at detecting rapid shifts in soil health?

Soil management induced shifts in nematode food webs within a Mediterranean vineyard in the Central Coast of California (USA)

Soil health and sustainability: managing the biotic component of soil quality

A critique of the soil health framework is that biological indicators currently lag behind chemical and physical indicators of soil health. Incorporating nematode communities into the soil health framework could help to better reflect key aspects of soil food web structure and function and significantly contribute to ecosystem processes. However, little is understood regarding how nematode communities relate to soil biological health indicators such as permanganate oxidizable carbon (POXC), soil protein, mineralizable C, and enzyme activities in agroecosystems. Here, we use an exploratory factor analysis (EFA) to quantitatively explore which set of soil health indicators best explain a given factor (i.e. soil health trait) using data from two long term experimental trials and 44 farm fields across Ohio. Specifically, this paper aims to 1) integrate our understanding of nematode structure and function with other soil biological health indicators to describe soil health traits; and 2) determine how management practices alter soil health traits. We found that soil biological health indicators represented four underlying soil health traits: fungal organic matter processing pathway, the rate of nutrient cycling, trophic complexity, and cumulative disturbance. Results indicated that soil biological health indicators, such as enzyme activities, POXC, mineralizable C and soil protein were more integrated with nematode feeding groups than with nematode indices. Additionally, tillage intensity had a significant effect on the fungal organic matter processing pathway and the rate of nutrient cycling. This study indicates that nematode feeding groups can be readily incorporated into the soil health framework and future soil health assessments.

Soil health is a matter of growing concern because of its degradation due to unsustainable anthropogenic activities over the last few decades. It is maintained by interactions among the components of the soil food web commonly concentrated in the vicinity of the plant roots, called the rhizosphere. The soil food web is dominated by nematodes. They occupy various trophic positions because of their diverse feeding habits. The free-living forms are mainly dependent on soil bacteria and fungi for their nutrition, while the parasitic forms feed on plant roots. The population of these two groups is regulated by the activities of predatory nematodes which can be carnivorous or omnivorous. The soil nematodes thereby partake responsibilities in nutrient cycling, mineralization and decomposition pathways which, in turn, affects the aboveground productivity. This intricately connected food web structure is vulnerable to disturbances like increased soil salinity, acidity, nitrogen enrichment, tillage, crop rotations, fertilizers, pesticides, soil amendment techniques and heavy metal pollution. The effects are reflected by alterations in the abundance and diversity of soil nematodes belonging to various trophic groups. These alterations have been formulated into measurable indices like maturity index (MI), structure index (SI), enrichment index (EI) and channel index (CI). The faunal profile and metabolic footprints of soil nematodes are latest developments in the field of nematode community analyses. Though these indices cannot replace the conventional soil ecotoxicological assays, they can give added information about soil biology which can be utilized to design sustainable land use practices.

We conducted a laboratory study using soil cores to determine whether anecic earthworm (Lumbricus terrestris) burrow linings (the drilosphere) are sites for enhanced carbon and nitrogen mineralization and increased microbial biomass and nematode abundance. We compared microbial biomass C, C mineralization rates, metabolic quotient, levels of inorganic N (NO3/- and NH4/+), and nematode abundance over the course of 11 weeks in soil from earthworm burrows, bulk soil away from burrows, and a control soil in cores to which no earthworms were added. Significant differences were observed in microbial biomass carbon, which was 38 to 84% lower, and carbon mineralization and metabolic quotient, which were 2.3 to 7.5 and 5.6 to 17.4 times, respectively, higher in burrow than in control soil. No significant differences were observed in these variables between bulk and control soil. In addition, nematodes were 3.7 to 6.5 times more abundant, and inorganic N levels 21 to 78% higher in burrow than in control soil, with no significant differences observed between bulk and control soil. Dynamics of microbial biomass carbon and inorganic N followed the same general pattern in burrow, bulk, and control soil. By contrast, dynamics of nematode abundance, carbon mineralization, and metabolic quotient differed between burrow and both bulk and control soil, with peak values observed at 5, 7, and 11 weeks for nematode abundance, C mineralization, and metabolic quotient, respectively. Our results suggest that earthworms may have an indirect effect on soil C and N dynamics by stimulating the activities of nematodes and their interaction with microbial biomass in the drilosphere to a greater degree than is observed in soil that has not come in direct contact with earthworms.

Intergovernmental Panel on Climate Change (IPCC) Tier 1 methodologies commonly underpin project‐scale carbon accounting for changes in land use and management and are used in frameworks for Life Cycle Assessment and carbon footprinting of food and energy crops. These methodologies were intended for use at large spatial scales. This can introduce error in predictions at finer spatial scales. There is an urgent need for development and implementation of higher tier methodologies that can be applied at fine spatial scales (e.g. farm/project/plantation) for food and bioenergy crop greenhouse gas (GHG) accounting to facilitate decision making in the land‐based sectors. Higher tier methods have been defined by IPCC and must be well evaluated and operate across a range of domains (e.g. climate region, soil type, crop type, topography), and must account for land use transitions and management changes being implemented. Furthermore, the data required to calibrate and drive the models used at higher tiers need to be available and applicable at fine spatial resolution, covering the meteorological, soil, cropping system and management domains, with quantified uncertainties. Testing the reliability of the models will require data either from sites with repeated measurements or from chronosequences. We review current global capability for estimating changes in soil carbon at fine spatial scales and present a vision for a framework capable of quantifying land use change and management impacts on soil carbon, which could be used for addressing issues such as bioenergy and biofuel sustainability, food security, forest protection, and direct/indirect impacts of land use change. The aim of this framework is to provide a globally accepted standard of carbon measurement and modelling appropriate for GHG accounting that could be applied at project to national scales (allowing outputs to be scaled up to a country level), to address the impacts of land use and land management change on soil carbon.

Changes in diversity patterns and assembly processes of soil nematode communities during forest secondary succession on the Loess Plateau

Solar parks are a rapidly expanding novel land use primarily to produce renewable energy. However, the aim is to make them multifunctional, and limit negative impacts on soils or even improve soil quality. Solar panels change the microclimate and cause shading below the panels, influencing plant growth and carbon and water inputs to the soil, with potential cascading effects on the soil biota. This research aimed to test the effect of solar panels on earthworm and nematode communities in 12 solar parks with contrasting designs across the Netherlands. Earthworm abundance and diversity, plant biomass and nematode abundance were measured between (gap) and below the solar panels. Nematode abundance was also measured at the highest and lowest edges of the panels. Plant biomass, nematode abundance and earthworm abundance were all significantly lower below the solar panels compared to in the gap between the panels. Nematode abundance at the highest and lowest edges showed intermediate numbers compared to the gap and below the panels. These results show that solar parks have a large impact on the soil biota and stress the need for guidelines for ecologically sound solar park designs to prevent soil damage.

Changes in the composition of the plant-feeding nematode community in grasslands after cessation of fertiliser application

ABSTRACTAs the reality of a carbon-neutral market and future takes form, all available resources will need to be focused upon removing carbon dioxide from the atmosphere. In this regard, no alternative is more promising today than nature-based solutions. Restoration of native ecosystems and the use of management concepts such as adaptive multi-paddock (AMP) grazing for ranchland have the potential to reliably store vast amounts of carbon in near-surface soil at very low cost. If only half of the existing US grazing lands is managed differently than now, these healthy soils could store from 10 to 23 percent of US carbon dioxide emissions every year. Moreover, healthy soils will significantly enhance the economic profitability and drought and flood resilience of ranches. To date, no trading system meets the needs and requirements of the private landowners that control the land that has the ability to sequester these immense amounts of carbon dioxide. The Soil Value Exchange (SVX) is designed to support landowners as they manage their property to promote healthy soils and soil carbon storage by (1) implementing a soil-carbon trading system based on robust soil carbon measurements that works for land owners and carbon credit buyers, (2) providing grants for land management consultant support, and (3) providing grants to support soil carbon measurements. SVX has established collaborations with expert land consultancy organizations and has a goal of enabling the storage of 10 million metric tons of carbon dioxide each year in 2024 and 100 million metric tons of carbon dioxide credits each year in 2028.

Fluopyram (Velum® One) is a synthetic nematicide and azadirachtin (Molt-X®) is a biological nematicide. Both have shown promise against plant-parasitic nematodes on several agriculturally important crops. There is a lack of information on integration of pre-plant sunn hemp (Crotalaria juncea) cover crop with these post-plant nematicides, aiming to improve plant-parasitic nematodes management and mitigate any detrimental effects on free-living nematodes. Three field trials were conducted to investigate the effects of fluopyram alone or in combination with pre-plant sunn hemp cover crop, and azadirachtin combined with pre-plant sunn hemp on Rotylenchulus reniformis and Meloidogyne spp., and free-living nematodes. Zucchini (Cucurbita pepo) and tomato (Solanum lycopersicum) were grown in Trials I and II, and sweet potato (Ipomoea batatas) only was grown in Trial III. In all three trials, early applications of fluopyram at crop planting were effective in suppressing the abundance of Meloidogyne spp. (M. incognita and M. javanica) but it was not effective in reducing R. reniformis in the soil. Combining sunn hemp with fluopyram was suppressive to R. reniformis on short-term zucchini crop, but not on longer term tomato and sweet potato crops. In addition, application of fluopyram at transplanting was the key to successful suppression of Meloidogyne spp. as later fluopyram chemigation (at 2 weeks after planting in Trial II or 1 month after planting in Trial III) had no effect against Meloidogyne spp. On the other hand, planting of sunn hemp followed by monthly post-plant azadirachtin application consistently suppressed R. reniformis, but this treatment did not suppress Meloidogyne spp. Integrating sunn hemp with fluopyram increased zucchini yield by >2.3 folds and that with azadirachtin increased the zucchini yield by >1.7 folds. Although no yield improvement was observed on tomato in Trial II, integrating sunn hemp with azadirachtin and fluopyram increased tomato yield by 0.23 and 1.12 folds, respectively, in Trial I. Marketable yield of sweet potato was increased by 4.5–6.4 folds in all the fluopyram treatments but was only increased 61.5% by sunn hemp plus azadirachtin treatment. While fluopyram alone often reduced the abundance of free-living nematodes, integrating with sunn hemp mitigated the negative impacts of fluopyram on soil health.

To achieve efficient and precise classification of nematode community distribution in tea garden soils of the Qinba Mountains, this study integrated a backpropagation neural network (BP-NN) with a convolutional neural network (CNN) to construct a BP-CNN model, which was applied to assess soil health in tea gardens within this region. Multiple gradient sampling points were established in typical tea gardens across the Qinba Mountains. Samples were collected at varying altitudes and soil types to obtain nematode community species composition, abundance, and environmental factor data. Using nematode community characteristics as input and soil health grades as output, the BP-CNN model was constructed. CNN extracted deep features from the data, while BP-NN performed classification predictions. The model was validated against standalone BP-NN and CNN models. Results indicate the BP-CNN model achieved a grading accuracy of [XX%], significantly outperforming single models. Tea garden soil nematode communities in the Qinba Mountains can be classified into [X] grades, each corresponding to specific soil physicochemical properties and elevation ranges. The abundance of dominant groups such as bacteriophagous nematodes and fungivorous nematodes serves as a core indicator for grading. This study demonstrates that the BP-CNN model can effectively classify nematode communities in tea garden soils within this region, providing a tool for intelligent soil health assessment. Its classification results also offer scientific basis for tea garden soil management.

Ecosystem type affects interpretation of soil nematode community measures

In Europe soil health is facing emerging challenges that require innovative solutions and policy interventions. We acknowledge that 62% of the European Union (EU) soils are not in healthy condition, while we face serious challenges such as climate change, food security, biodiversity loss, and socio-economic pressures. The severity of these issues is evident in the fact that soil erosion is unsustainable for around ¼ of the EU territory, carbon stocks in soils are declining, nutrients are depleting, and emerging contaminants can pose a serious threat to soil and human health. The costs of soil degradation in the EU may reach up to €70 billion per year, highlighting the urgent need for action. To address these challenges, the EU has put in place many policies for agro-environmental protection since 2000, including soil protection. The European Green Deal, launched in 2020, has set an ambitious roadmap to make the EU the first carbon-neutral continent with a modern, competitive, and resource-efficient economy. As part of the Green Deal, the European Commission (EC) has put soil protection in a high position on the EU policy agenda, recognizing that healthy soils are essential to achieve climate neutrality, zero pollution, sustainable food provision, and a resilient environment. This increased focus on soil health has led to the development of new policies and initiatives, such as the Soil Monitoring and Resilience Directive, which aims to establish a common framework for monitoring and assessing soil health in the EU. The Soil Monitoring and Resilience Directive, in place since December 2025, lays down measures for monitoring and assessing soil health, managing soils sustainably, and restoring contaminated sites. Furthermore, the Mission Soil, which aims to set up 100 Living Labs to promote sustainable land and soil management in urban and rural areas, will play a crucial role in achieving the objective of healthy soils by 2050. With an estimated investment of nearly €800 million until 2028, funded research projects under the Mission Soil are expected to reverse soil degradation through action on the ground, underpinned by the development and monitoring of a set of indicators. In addition to these initiatives, the Carbon Removals and Carbon Farming (CRCF) regulation is the first EU volunteer framework for certifying carbon removals and carbon farming. This regulation will monitor, report, and verify carbon removals, soil emission reduction, and biodiversity benefits, providing a new opportunity for farmers and other stakeholders to contribute to climate change mitigation. The carbon farming framework can also serve as an interesting business model for additional income to farmers, while involving diverse actors such as certification bodies, auditors, tech industry, and creating new jobs. By promoting sustainable land use practices, the CRCF regulation can help sequester carbon, reduce greenhouse gas emissions, and improve soil health. This presentation will discuss these EU soil policies in detail, with a specific focus on the role and activities of the EU Soil Observatory (EUSO). Overall, the presentation will show how the EU soil policies and the EUSO are advancing the data, knowledge and tools on soils and leading the transition towards healthy soils in the EU.

Land management changes are and will continue to play a substantial role in national and global strategies towards decarbonisation goals. Yet, roles for land managers and their communities to co-create opportunities for just transitions are not well represented or accounted for in policy instruments or markets, including those for carbon offsets. Understanding regional context is critical to identify strategies for land management changes to underpin just transitions. We outline a mixed-methods approach involving an analysis of socio-economic data and a critical review of regional plans to identify the benefit aspirations that communities have articulated, and the drivers of transitions already at play to understand how land sector carbon abatement projects could support regional transitions. This approach is demonstrated using a case study region in Queensland, Australia. The case study region hosts land sector carbon abatement projects under a national policy that incentivises least cost abatement and under a state policy that incentivises land sector carbon abatement with bundled environmental and social co-benefits. The results show that across sectors and locations, communities are seeking economic, cultural, and social outcomes that can be delivered as co-benefits of land management changes for carbon abatement. Our analysis shows that the value of multiple co-benefits is place-specific and dependent on the provenance of land management changes and broader regional conditions. By understanding regional contexts and aspirations, it is possible to identify how and where land sector carbon abatement investments can be negotiated between investors and communities to support just transitions to low-carbon futures.