Soil Health Assessment Research Articles

Mapping of the Susceptibility of Colombian Musaceae Lands to a Deadly Disease: Fusarium oxysporum f. sp. cubense Tropical Race 4

Fusarium oxysporum f. sp. cubense Tropical Race 4 (Foc TR4) (Syn. Fusarium odoratissimum) is a devastating soil-borne pathogen that infects the roots of banana plants and causes Fusarium wilt disease. Colombia is one of the world’s leading banana producers; therefore, new uncontrolled outbreaks could have serious consequences. Despite this, little is known about the susceptibility of Musaceae lands in Colombia to Foc TR4. This work presents a pioneering study on the susceptibility of Colombian soils to Foc TR4. For this, a study was carried out to characterize climatic, edaphic, and density factors of Musaceae productive systems at the Colombian level, articulated with expert criteria to map and define areas with different levels of susceptibility to Foc R4T. These criteria are typically selected based on the existing scientific literature, consultation with domain experts, and consideration of established methods for assessing soil health and disease susceptibility in Musaceae plantations. By joining the analyzed susceptibility factors, differentiated areas were generated that imply a greater or lesser predisposition to the disease. Subsequently, a validation of the classification was made with Random Forest. The results indicate that at the level of climate, soil, and farm density as a fit factor, practically 50% of the cultivated territory of Musaceae are areas high and very highly susceptible to the pathogen (572,000 km2). The results showed that from the total Musaceae area, Antioquia, Bolívar, Chocó, and Santander turned out to be the departments with the highest proportion of very high susceptibility class of the production farms. The analysis of Random Forest classification performance shows that the model has a relatively low out-of-bag (OOB) error rate (0.023). The study on the susceptibility is highly novel and original, as it represents the first systematic investigation of Foc TR4 susceptibility in Colombian soils. This paper provides important insights into the susceptibility of Musaceae lands in Colombia to Foc TR4. The study highlights the need for ongoing monitoring, containment, and control measures to prevent the spread of this deadly pathogen and protect Colombia’s important banana industry.

Assessment of soil health in uncontrolled grazing areas in the Administrative Post of Luro, Lautem, East Timor

Abstract. Costa DD. 2023. Assessment of soil health in uncontrolled grazing areas in the Administrative Post of Luro, Lautem, East Timor. Intl J Trop Drylands 7: 46-54. Uncontrolled grazing practices have been judged as the main cause of soil degradation in grassland areas. This study was conducted to provide baseline information on soil health in uncontrolled grazing areas in the administrative post of Luro, municipality of Lautem, East Timor (Timor Leste). Furthermore, 40 soil samples were collected from eight uncontrolled grazing areas using the core method; five points sampling per each site (four in corners and one in in the center) sampling points distances were 100 to 150 m apart, and each point represented three different soil layers (0-5 cm, 5-10 cm, and 10-20 cm). All soil samples were transported to the laboratory of the Faculty of Agriculture, Universidade Nacional Timor Lororsae, East Timor. Samples preparation and analysis followed the procedure and guidelines of McKenzie et al. (2002) and Liu et al. (2019) for physical properties, while Soil Organic Matter (SOM) analysis used Loss-On-Ignition (LOI) adopted from Nakhli et al. (2019). In addition, all soil chemical properties were analyzed using Kjeldhal and Bray-1 method following the soil analysis guidelines of JICA (2014). The study showed that soil physical properties in the uncontrolled grazing areas in Luro are characterized by high bulk density, poor porosity, and low organic matter content. Furthermore, soil pH remains neutral in areas where uncontrolled grazing is practiced but with very low nitrogen and potassium levels. In contrast, phosphorus is very high in the Cotamuto and Lakawa but very low in the Afabubo areas. Furthermore, low literacy levels and livelihoods are key socioeconomic factors that directly influence uncontrolled grazing practices. Hence, promoting sustainable grazing methods among communities towards raising livestock for their livelihood is recommended.

Divergent soil health responses to long-term inorganic and organic fertilization management on subtropical upland red soil in China

To optimize soil health, land use, and soil management decisions need to be guided by an understanding of the underlying soil health. Although widely used fertilizers guarantee crop production, they ultimately damage agricultural soil environmental quality and threaten the overall food chain safety. Thus, an integrative assessment considering both environmental safety and soil fertility is required for the sustainable development of long-term fertilization systems. In this study, we conducted a comprehensive assessment of soil health using 20 soil physical, chemical, and biological indicators and assessed them according to four heavy metals—copper, zinc, cadmium, and lead. This experiment was conducted in an area where there is an ongoing, 23-year-long fertilization experiment in a typical red soil region of southern China, including four treatments of common inorganic chemical fertilizer (CF), CF mixed with micronutrients (CF + T), CF mixed with pig manure (PM), and PM mixed with micronutrients (PM + T). To assess the soil fertility quality, we selected a minimum data set consisting of soil water-stable aggregates mean weight diameter, available phosphorus, total nitrogen, microbial biomass carbon, and dehydrogenase activity. The results revealed that soil fertility quality followed the order of PM + T ≈ PM > CF + T > CF. We also used a modified potential ecological risk index to assess the soil environmental quality. This approach considered the acid-soluble and exchangeable fraction of heavy metals as the bioavailability component. Both PM and PM + T treated soils were significantly contaminated by heavy metals, with particularly large amounts of Cd contamination. The soil health index escalated from CF, CF + T, PM to PM + T, which indicated that the use of pig manure allowed for more fertile soil relative to standard chemical fertilization. Moreover, applying additional micronutrients also had a significant influence on soil fertility. Therefore, our study revealed that long-term fertilization using organic pig manure was beneficial to overall soil fertility; however, these benefits were coupled with significant limitations regarding heavy metal contamination. Collectively, this study provides a better supporting method for soil health management and long-term fertilization strategies.

Soil health assessment for different tillage and cropping systems to determine sustainable management practices in a humid region

Various soil indicators can be chosen for soil health assessment. The important indicators representing overall soil health need to be carefully selected to reduce the cost and time involved in sampling and testing, which can be achieved by establishing a minimum data set (MDS). The objective of this paper was to identify the indicators that are important for assessing soil health in northeast Mississippi and establish an MDS. Values for chemical, physical and biological indicators obtained from three treatments (no-fertilized control, no-organic fertilizer and poultry litter) in five different field experiments were used to screen MDS. The methodology followed a combination of principal component analysis (PCA), cluster analysis and expert’s opinion (EO) method. Results showed that the correlation between the MDS and total data set (TDS) was high (R2 =0.94). The chosen MDS included four chemical indicators (pH, organic carbon, total nitrogen and Mehlich-3 phosphorus), three physical indicators (bulk density, water-stable aggregate stability, available water capacity), and two soil biological indicators (dehydrogenase activity, heterotrophic plate count). When the selected chemical MDS was applied to all treatments of the five experiments, the MDS and TDS data fitted well (R2 =0.81), indicating that the soil indicators included in the MDS were the most important for soil health in this study. In conclusion, an MDS for soil health assessment was established for the experiments in northeast Mississippi. The results can provide fundamental guidance for researchers, growers, and stakeholders to evaluate soil health and optimize soil management.

Exploring the microbial response as a potential bio-indicator for soil health: Insights from a controlled incubator experiment

Soil microorganisms are known to be sensitive to disturbances in their surroundings, and those microbial shifts can reflect the soil health status. Therefore, these shifts can potentially be used as a bio-indicator for soil health. However, measurements taken directly on field samples are often affected by strong spatiotemporal trends that are not related to the soil health status. To address this issue, this study aimed to understand whether the response of the bacterial and fungal soil communities after short-term disturbances in a controlled incubator experiment has the potential to reflect the soil health status. The study was conducted on two arable soils with contrasting health status, which was determined based on extensive background information up to ten years. We studied the response of the soil bacterial and fungal communities after short-term disturbances (drying-rewetting and/or chitin amendment, consecutive disturbances). These disturbances were selected because drying and rewetting alters the moisture dynamics and consequently the dynamics of the bacterial and fungal communities, whereas chitin application releases nitrogen into the soil and boosts the microbial biomass and activity. Three techniques were applied and compared to study the response in the bacterial and fungal communities: metabarcoding (relative changes), PLFA analysis (absolute biomass) and HWC (labile C fraction). Using metabarcoding, the soil microbial communities gave a consistently greater response in the less healthy soil after short-term disturbances. More specifically, shifts upon drying and rewetting were up to two- to three-fold larger in the less healthy soil compared to the healthy soil. Soils that were exposed to drought for a second time were less responsive, even for the less healthy soil, indicating that a legacy effect is present. Whereas we expected that chitin could at least partially reduce the effects of drought, the combination of both disturbances led to more shifts in the microbial community, but mostly in the less healthy soil. Shortly after disturbances, the response of the bacterial and fungal soil communities measured by metabarcoding, in a pot trial, reflected the soil health status. The magnitude of the response for bacteria and fungi were both valuable for the assessment of soil health. Traditional soil health indicators like HWC and PLFA, but also DNA-related indicators such as diversity and taxonomical indicators were less sensitive to measure this response. This leads us to recommend the magnitude of the response of bacteria and fungi analyzed shortly after disturbances and measured with metabarcoding, being a consistent and sensitive bio-indicator for soil health. Availability of data and materialsThe raw demultiplexed sequence data are available in the NCBI Sequence Read Archie under accession number PRJNA735907. Scripts used to run all data analysis can be found at https://gitlab.com/lljoos/soilmicrobiome_droughtrewettingchitin.

High-throughput soil health assessment to predict corn agronomic performance

Developing high-throughput methods to quantify soil health can support decision making to minimize soil constraints for crop growth and increase sustainability in agroecosystems. This study evaluated the ability of soil health assessment conducted at the beginning of the crop growing season to predict corn agronomic performance in nutrient fertilization trials. We compared different methods to assess soil health, from the most traditional approach of measuring individual soil biochemical indicators to more novel approaches using diffuse reflectance infrared Fourier transform spectroscopy (mid-DRIFTS). Soil health was quantified using: I) traditional and emerging biochemical soil health indicators (up to 20 soil indicators), II) mineral and organic functional groups abundances estimated as peak areas in mid-DRIFTS, and III) mid-DRIFTS with partitioned spectra and partial least squares regression. Corn response to fertilizer was evaluated in a) phosphorus, potassium, and sulfur omission trials (2016–2018; 41 sites across 17 Ohio counties) as well as in b) N rates trials (2016–2017; 25 fields across 14 Ohio counties). Modeling using either biochemical soil health indicators or mid-DRIFTS accurately predicted corn yield across nutrient treatments in omission trials (R2V=0.61–0.84 in validation sets) and unfertilized controls in N rates trials (R2V=0.68–0.81) as well as corn N-driven yield gap (i.e., delta yield defined as grain yield at agronomic optimum N rate minus grain yield of the control, R2V=0.64–0.76) in N rates trials. Mid-DRIFTS approaches equaled or outperformed the predictive ability of measured biochemical soil health indicators in estimating crop performance (up to 38 % improvement in R2V), unveiling a promising method to more efficiently assess soil health. Early season soil health assessment via mid-DRIFTS has potential to directly estimate corn agronomic performance.

Changes in the health of metal-contaminated soil before and after stabilization and solidification

Stabilization is popularly employed to remediate metal-contaminated soils. It involves the absorption and precipitation of heavy metals to reduce their solubility, movement characteristics, or risk and toxicity. This study aimed to conduct a soil health assessment to determine changes in the health of metal-contaminated soil before and after the application of five stabilizers (acid mine drainage sludge (AMDS), coal mine drainage sludge (CMDS), steel slag, lime, and cement). Soil health assessment, including three soil functions, namely soil productivity, soil stability, and soil biodiversity, evaluated the physical, chemical, and biological indicators (total 16 indicators). Soil health index (SHI) of soil function was calculated by multiplying each indicator score by the weighting factor of each indicator. Total SHI was obtained by summing the three soil-function SHI. Total SHI of the stabilized and test soils followed the order as control soil (1.90) > heavy metal-contaminated soil (1.55) > CMDS-stabilized soil (1.29) > steel slag-stabilized soil (1.29) > AMDS-stabilized soil (1.26) > cement-stabilized soil (0.74) > lime-stabilized soil (0.67). Total SHI of the initial heavy metal-contaminated soil was evaluated as ‘normal’, before the stabilizer was applied; however, most of the stabilized soils became ‘bad’ after application of the stabilizers. Furthermore, soils stabilized by cement and lime showed very poor soil health. The results implied that changes in physical and chemical soil properties occurred due to the disturbance caused by the mixing of stabilizers, and ions eluted from the stabilizers could deteriorate soil health further. The findings indicated that soil treated with stabilizers is not suitable for agricultural purposes. Overall, the study suggested that stabilized soil from metal-contaminated sites should be covered with clean soil or monitored for some time before deciding its future agricultural use.

Assessing soil health following conversion from forestry to pasture in Canterbury

Soil health was assessed across land conversions from forestry (Pinus radiata) to irrigated dairy pasture. Samples were collected and indicators of soil fertility, organic matter, soil physical condition and biological activity assessed. Soil health scores were calculated from the indicators and distance from optimum shown in radar plots. Soil health was improved for pastoral land use following conversion from forestry. The timesince forestry ceased and irrigation commenced had a signification effect on indicators of soil health, although many were not optimum even for the sites longest out of forestry/under irrigation. The main factors contributing to lower scores across all sites were suboptimal fertility,high C:N ratios, high macroporosity, low microbial respiration and low earthworm abundance and diversity. Some aspects (e.g., fertility) could be managed through nutrient application, while other aspects are more difficult to manage (e.g., C:N ratio and biological activity). Management targeting these properties may accelerate the path to a healthy and well-functioning soil. The inclusion of a wider range of indicators can help to better understand and manage soils during the conversion from forestry to pasture. This approach could be useful across all pasture systems to help ensure well-functioning soils.

Forest restoration rehabilitates soil multifunctionality in riparian zones of sugarcane production landscapes

Brazilian sugarcane plays a vital role in the production of both sugar and renewable energy. However, land use change and long-term conventional sugarcane cultivation have degraded entire watersheds, including a substantial loss of soil multifunctionality. In our study, riparian zones have been reforested to mitigate these impacts, protect aquatic ecosystems, and restore ecological corridors within the sugarcane production landscapes. We examined (i) how forest restoration enables rehabilitation of the soil's multifunctionality after long-term sugarcane cultivation and (ii) how long it takes to regain ecosystem functions comparable to those of a primary forest. We investigated a time series of riparian forests at 6, 15, and 30 years after starting restoration by planting trees (named ‘active restoration’) and determined soil C stocks, δ13C (indicative of C origin), as well as measures indicative of soil health. A primary forest and a long-term sugarcane field were used as references. Eleven soil physical, chemical, and biological indicators were used for a structured soil health assessment, calculating index scores based on soil functions. Forest-to-cane conversion reduced 30.6 Mg ha−1 of soil C stocks, causing soil compaction and loss of cation exchange capacity, thus degrading soil's physical, chemical, and biological functions. Forest restoration for 6–30 years recovered 16–20 Mg C ha−1 stored in soils. In all restored sites, soil functions such as supporting root growth, aerating the soil, nutrient storage capacity, and providing C energy for microbial activity were gradually recovered. Thirty years of active restoration was sufficient to reach the primary forest state in overall soil health index, multifunctional performance, and C sequestration. We conclude that active forest restoration in sugarcane-dominated landscapes is an effective way to restore soil multifunctionality approaching the level of the native forest in approximately three decades. Moreover, the C sequestration in the restored forest soils will help to mediate global warming.

Applicability of soil health assessment for wheat-maize cropping systems in smallholders’ farmlands

Soil health assessment is fundamental to guiding sustainable soil management practices, ensuring healthy soil, crop productivity, and provision of other ecosystem services. Interpretation of soil health in intensive agriculture in the North China Plain (NCP) is still lacking due to an over emphasis on soil chemical management and large variations among smallholders’ farmlands. The objectives of this study were to (i) compare soil health assessment approaches in response to fertilization regimes, (ii) quantify relationships between soil health and agronomic outcomes, (iii) develop a minimum data set to simplify soil health assessment, and (iv) validate soil health assessment frameworks in smallholders’ fields on the NCP. We collected soil samples from eight wheat-maize rotation long-term experiments which were divided into three fertilization regimes: (1) NPK, application of chemical fertilizers only; (2) M, application of organic materials only; and (3) MNPK, combined application of organic materials with chemical fertilizer application. Three soil health indexing (SHI) approaches, Comprehensive Assessment of Soil Health (SHI-CASH), linear (SHI-L) and sigmoidal (SHI-Sig) were evaluated. SHIs in the M and MNPK treatments were significantly higher than those in the NPK treatment across assessment approaches and were positively correlated with maize yield. A minimum data set including subsurface hardness, wet aggregate stability, available K, available Fe, soil organic carbon and soil protein was established using best subset regression. The soil health indices of smallholders’ farmlands using CASH and MDS were 0.58 (0.42–0.73) and 0.63 (0.40–0.87), respectively. More than 60% smallholders’ fields was at middle or low level. The relationship between SHI-CASH and SHI-MDS (Sig) was better than those for the CASH and linear methods. Our results demonstrate that an MDS based on best subset regression is applicable for evaluating soil health in wheat-maize rotation systems in the NCP. Soil health assessment in smallholders’ farmland indicates that soil health constraints are related to soil and biomass management, which provides insights on pathways towards addressing soil health gaps.

Soil community catabolic profiles for a semiarid reclaimed surface coalmine

ABSTRACT Recovery of soil health offers insights into the mechanisms underpinning the stability of remediated ecosystems. Indirect assessment of enzymatic activity potential using substrate induced respiration (SIR), is commonly used to evaluate changes in soil microbial activity profiles, with their links to environmental and management factors. In this study, community level physiological profiling (CLPP) was employed to assess the impact of time on surface coal mine soil remediation. When compared with an adjoining control site, analysis of CLPP parameters offer useful insights and prospective tools for assessing soil health, following mining and remediation activities.

Soil Health Assessment and Management Framework for Water-Limited Environments: Examples from the Great Plains of the USA

Healthy soils provide the foundation for sustainable agriculture. However, soil health degradation has been a significant challenge for agricultural sustainability and environmental quality in water-limited environments, such as arid and semi-arid regions. Soils in these regions is often characterized by low soil organic matter (SOM), poor fertility, and low overall productivity, thus limiting the ability to build SOM. Soil health assessment frameworks developed for more productive, humid, temperate environments typically emphasize building SOM as a key to soil health and have identified the best management practices that are often difficult to implement in regions with water limitations. This study reviewed existing soil health assessment frameworks to assess their potential relevance for water-limited environments and highlights the need to develop a framework that links soil health with key ecosystem functions in dry climates. It also discusses management strategies for improving soil health, including tillage and residue management, organic amendments, and cropping system diversification and intensification. The assessment of indicators sensitive to water management practices could provide valuable information in designing soil health assessment frameworks for arid and semi-arid regions. The responses of soil health indicators are generally greater when multiple complementary soil health management practices are integrated, leading to the resilience and sustainability of agriculture in water-limited environments.

Assessment of Earthworm Viability and Soil Health after Two Years of Raw and Composted De-Inking Paper Sludge Amendment

The improvement of soil fertility properties is a priority for meeting sustainable development goals and world food security. One potential benefit of using paper sludge in agriculture is the reduction of waste and associated environmental impacts. By using paper sludge as a soil amendment, it is possible to divert away this material from landfills and instead use it to improve soil fertility and support the growth of crops. However, it is important to note that paper sludge may contain contaminants harmful to plants and soil health, of which earthworm viability serves as a key indicator. The present investigation aimed to evaluate changes in soil properties after the application of raw and composted de-inking paper sludge for two years. Accordingly, a field study was conducted in Manouba, a semi-arid region of Tunisia with a clay loam soil. The raw de-inking sludge (DS) and composted de-inking paper sludge (DSC) were applied at 30 and 60 t ha−1 and 20 and 40 t ha−1, respectively. Soil treatments were compared to unamended soils (C), to determine the optimal sludge treatment and rate for increasing the soil quality. Soil chemical (soil organic matter SOM, total carbon TC, and nitrogen TN, nutrient soil contents organic matter fractioned), physical (porosity and structural stability), and biological parameters (earthworms viability) were assessed. The results showed an increase of soil OM in the DS and DSC amended soils with the lowest rates (30 and 20 t ha−1). The humic fraction was found to be the dominant form. TC and TN were improved in the DS and DSC amended soils with the highest rates: 60 (DS2) and 40 t ha−1 (DSC2). Phosphorus and potassium were also increased in a dose-dependent manner. However, the soil porosity decreased in all treatments. The composted de-inking sludge was toxic for epigeic species, which could be explained by the use of litter while composting. Overall, the application of DS and DSC at low rates (30 and 20 t ha−1, respectively) might be a promising alternative for improving soil quality and at the same time ensuring the proper management of these wastes.

Automated sensor-based quantification of soil water retention and microbial respiration across drying conditions

Understanding soil responses to climate-induced precipitation variability is important for improving global carbon models and the development of climate-resilient agriculture. However, our knowledge remains limited regarding factors that influence soil water dynamics and microbial respiration across drying conditions, partially hindered by the lack of easily accessible methodologies. We developed a low-cost, automated, and integrated system to simultaneously quantify microbial respiration and soil water retention in response to drought conditions. This system integrates a CO2 sensor and a digital scale, enabling continuous measurement of CO2 concentration and soil water loss by evaporation when soils are incubated with desiccants inside air-tight chambers. Here we show that the sensor platform provides accurate and repeatable CO2 measurements when compared to a spectroscopy gas analyzer and the alkali trap method. Using the sensor platform, we further demonstrated that averaged microbial respiration of rewetted soil over 4-day incubation declined as management intensity increased following the order of Till ≤ NoTill ≤ Till_fallow ≤ NoTill_fallow = Hay field < Forest. These soils were air-dried for two years before use in incubation experiments, and microbial respiration upon rewetting showed a unimodal response, which rapidly increased and peaked within 12 h except for in forest soils that exhibited a delayed response with respiration peaking at 30 h. Under drying conditions, rewetted soil from the Hay field showed lower water loss than other soils. Volumetric water content at the end of the drying period increased in the order of Till ≤ NoTill < Till_fallow ≤ NoTill_fallow = Hay field < Forest. We posit that this sensor platform provides a powerful tool for functional soil health assessments and fundamental understanding of soil water dynamics and microbial activities in responses to climate-induced water stress.

Rational Assessment of Physico-Chemical Parameters of Agricultural Soil from Selected Places of Banepa, Nepal

Physico-chemical parameters are among the basic attributes for the study of soil as they play a critical role in the assessment of soil health. In the present study, an attempt was made to study the physicochemical parameters in soil samples collected from six places of Banepa (Sinagal, Budole, Janagal, Chandeswori, Nayabasti, and Dhaneswor). The soil characterization was carried out for parameters like moisture content (%), pH, electrical conductivity (EC), chloride (Cl-), sulphate (SO42-), and phosphate (PO43-) ions. Chloride and sulphate were analyzed by argentometric titration and gravimetric method. The molybdenum blue method was employed for analysis of phosphate. In the present study, the pH of different soil samples ranged from 4.02-6.46 indicating a strongly to slightly acidic nature. EC values ranged from 0.05-0.45 mS/cm which showed that all soil samples were non-saline. The concentration of Cl-, SO42- and PO43- were in the range of 10142-16904 ppm, 1440-3907 ppm, and 1.8-3.8 ppm, respectively. Analysis of these parameters helps to determine the nature, fertility status of soil which is important for agricultural chemists for plant growth and soil management. Such studies provide the necessary information required to maintain optimum fertility year after year.

An identified agronomic interpretation for potassium permanganate oxidizable carbon

AbstractThe absence of clear empirical relationships between soil health and agronomic outcomes remains an obstacle to widespread adoption of soil health assessments in row crop systems. The objectives of this research were to (1) determine whether soil health indicators are connected to corn (Zea mays L.) productivity and (2) establish interpretive benchmarks for soil health indicators in Missouri. The objectives were accomplished by collecting corn grain yield at 446 monitoring sites (37 m2) in 84 commercial production fields in 2018–2020. Soil health and soil fertility samples were collected prior to planting at each site. These data, along with site‐specific soil and weather data, were modeled using traditional stepwise regression and nonparametric random forest (RF) and conditional inference forest (CIF) approaches. Root‐mean‐square errors were similar (1.4–1.5 Mg ha−1) with distinct R2 improvements over stepwise regression for both CIF (R2 = 0.45) and RF (R2 = 0.46) algorithms. Only seasonal rainfall and potassium permanganate oxidizable carbon (POXC) were included as top factors governing grain productivity in each model approach, thus demonstrating a regionally robust empirical relationship between POXC and grain productivity. Partial dependency analysis and two decision tree approaches identified 415 mg POXC kg−1 as a threshold for maximum grain productivity, providing a framework for regional interpretation of on‐farm soil health assessments. Little evidence was found connecting grain productivity with autoclaved citrate extractable protein and soil respiration. These findings underscore the power of POXC as an emerging soil health indicator to assess and quantify soil management effects on grain productivity.

Measuring the immeasurable: A structural equation modeling approach to assessing soil health

Soil health is recognized as an important ecosystem property sensitive to human impact. As a concept, soil health cannot be directly measured, and so assessment and modeling efforts largely rely upon key biological, chemical, and physical indicators. Efforts to develop an overall soil health index are largely lacking due to significant statistical challenges and the necessity for regional calibration. Taken from the field of educational research, structural equation modeling (SEM) is an attractive approach to enhance the reliability and validity of soil health scoring. Therefore, SEM may be utilized to advance research efforts to understand management practices impacts on soil health. Our objectives were to develop a robust scoring function that (i) captures the concept of soil health and latent variables, (ii) adjusts scores by inherent soil properties and legacy of intensive land use to adequately reflect our regional conditions and contemporary land management, and (iii) meets the diverse practitioner needs. Through this process, we refined our minimum dataset of soil health indicators and reconceptualized soil health indicators into functional properties. Our results support the development of a robust single level or a multilevel SEM model–depending on the practitioner's goals–that accounts for repeated sampling or pseudoreplication. While the SEM scoring functions were highly related to the conventional scoring approach, SEM outperformed the conventional methods in terms of its wider distribution of scores–and thus enhanced discriminatory power on the lower and higher range of scores. We also confirmed that the SEM scoring function that includes adjustments for mineralogy and legacy of intensive land use successfully differentiates among contemporary management practices and land use. Therefore, we have confidence that the tool is reliable and appropriate to further examine more nuanced impacts of land use change and management practices within a given land use across time and space covering a diversity of soils. (300 words).

A minimum suite of soil health indicators for North American agriculture

The concept of soil health is appropriately receiving increased attention from governments, producers, corporations, and other stakeholders because of the many functions of soil that support ecosystem services and farm profitability. With this interest, there is growing need to verify and monitor changes in soil health that result from how agricultural soil is managed. There are many indicators of soil health and, although this benefits the scientific community, it complicates interpretation across studies. The North American Project to Evaluate Soil Health Measurements (NAPESHM) assessed over 30 available measurements on 124 long-term agricultural research sites with replicated soil health treatments and created new pedotransfer functions. This analysis draws on findings from NAPESHM to identify a minimum suite of effective indicators of soil health for the North American Continent. The criteria for a minimum suite of effective indicators are that they (1) primarily reflect soil health rather than inherent soil properties or fertility, (2) are responsive to agricultural management practices that exemplify soil health principles, (3) are conducive to measuring soil health at scale in terms of cost and availability, and (4) are not redundant with regard to linking different soil functions to ecosystem services. Many indicators were determined effective for use in soil health studies and based on this analysis, soil organic C concentration, aggregate stability, and 24 h C mineralization potential were selected for the minimum suite of indicators. Using this minimum suite, as few as three laboratory measurements can be made to assess and track improvement in soil functioning as a result of soil management changes. These indicators may be supplemented with new pedotransfer functions to also estimate changes in available water holding capacity. This minimal suite of soil health measurements is recommended for scaling up soil health assessments across North America, and possibly beyond.

Ecological insights into soil health according to the genomic traits and environment-wide associations of bacteria in agricultural soils

Soil microbiomes are sensitive to current and previous soil conditions, and bacterial ‘bioindicators’ of biological, physical, and chemical soil properties have considerable potential for soil health assessment. However, the lack of ecological or physiological information for most soil microorganisms limits our ability to interpret the associations of bioindicators and, thus, their utility for guiding management. We identified bioindicators of tillage intensity and twelve soil properties used to rate soil health using a 16S rRNA gene-based survey of farmland across North America. We then inferred the genomic traits of bioindicators and evaluated their environment-wide associations (EWAS) with respect to agricultural management practice, disturbance, and plant associations with 89 studies from agroecosystems. Most bioindicators were either positively correlated with biological properties (e.g., organic matter) or negatively correlated with physical and chemical properties. Higher soil health ratings corresponded with smaller genome size and higher coding density, while lower ratings corresponded with larger genomes and higher rrn copy number. Community-weighted genome size explained most variation in health ratings. EWAS linked prominent bioindicators with the impacts of environmental disturbances. Our findings provide ecological insights into bioindicators of soil properties relevant to soil health management, illustrating the tight coupling of microbiome and soil function.

A holistic approach to assessing soil health

A holistic approach to assessing soil health In this Q&amp;A, Dr Christine Sprunger, Assistant Professor of Soil Health in the Department of Plant, Soil, and Microbial Sciences assesses the chemical, physical, and biological processes of performing soil health assessments. With her research focusing on the intersection of agriculture and the environment, Dr. Sprunger notes how soil health has gained heightened attention from both farmers and scientists because of its association with agronomic performance and environmental sustainability, evaluating soil respiration, active carbon, soil protein, beneficial free-living nematodes. Dr. Sprunger, in this interview, analyses the importance of soil health research, finding the link between soil health and ecosystem services, how climate change influences soil health, and the future of soil health research in a factsheet for farmers interested in soil assessment.