Indicators Of Soil Functioning Research Articles

Regional-scale assessment of soil functions and resilience indicators: Accounting for change of support to estimate primary soil properties and their uncertainty

Researchers and stakeholders are increasingly interested in evaluating soil functions and their relationships with soil physical resilience to prevent and mitigate natural and anthropogenic threats. This study aims to assess the effect of changing spatial support on estimating primary soil properties that are then used to map compound indicators of soil functions. The specific objectives are to determine the epistemic uncertainty associated with the estimates and assess the impact of accounting for the change-of-support when scaling up from the point- to the block-resolution.The study area is the southern Italian region of Campania, which is renowned for its high-quality agricultural and dairy products but is increasingly subject to soil disturbance and degradation. Seven primary soil properties (sand and clay contents, oven-dry soil bulk density, calcium carbonate, rock fragment, soil organic matter, and pH) were estimated over 75-m × 75-m blocks by jointly analyzing more than 3,000 point-based soil measurements with gridded terrain attributes by using multi-collocated block cokriging. Two compound soil indicators were then assessed from the maps of these soil properties: 1) the soil organic carbon stock (SOCS) in the entire region of Campania, and 2) the recharge transit time in the Sele alluvial plain where information about the mean annual depth to groundwater is available.The change-of-support proved to affect the total variance and the assessment of the extremes in the probability distributions of the primary soil variables. Our results emphasize that negative consequences occur when the change-of-support problem, upscaling in particular, is overlooked as happens when analyzing environmental data, especially for planning purposes and in the case of environmental risk assessment.

Soil function indicators are influenced by land use of different ages: A case study in a semi-arid region

Soil function refers to all the roles and services that the soil performs, and can be assessed by measuring physical, chemical and biological properties. In any case, studies on the state of fertility and biological activities are now emphasized as indicators of soil functions. Degradation of rangelands and their conversion to agricultural land is one of the most common land use changes in different parts of the world, with significant impacts on soil functions. Not much is known about the effects of land use change (especially rangeland to orchards of different ages) on soil function indicators in semi-arid areas. In the current study, the following five types of land covers were considered in a semi-arid region of northern Iran: (1) enclosured rangeland, (2) 10-year-old apple orchard, (3) 25-year-old apple orchard, (4) 10-year-old walnut orchard, and (5) 25-year-old walnut orchard. Results showed that the apple orchards (25-year-old) had a more fertile soil and a higher biological activity than the other land uses studied. Based on heat plots of soil properties under different land uses, the apple orchards (25-year-old) formed hot spots of soil functional indicators in the study area, followed by the walnut orchard (25-year-old) > enclosured rangeland > apple orchard (10-year-old) > walnut orchard (10-year-old). Although the conversion of natural lands (i.e., rangelands) to anthropogenic ones (i.e., orchards) is generally associated with negative feedbacks, tree species can be used (by creating forested rangeland or a combination of rangeland-agriculture) in areas with low soil function to improve soil conditions (in the long term).

Monitoring changes in global soil organic carbon stocks from space

Soils are under threat globally, with declining soil productivity and soil health in many places. As a key indicator of soil functioning, soil organic carbon (SOC) is crucial for ensuring food, soil, water and energy security, together with biodiversity protection. While there is a global effort to map SOC stock and status, SOC is a dynamic soil property and can change rapidly as a function of land management and land use. Here, we introduce a semi-mechanistic model to monitor SOC stocks at a global scale, underpinned by one of the largest worldwide soil database to date. Our model generates a SOC stock baseline for the year 2001, which is then propagated through time by keeping track of annual landcover changes obtained from remote sensing products with loss and gain dynamics dependent on temperature and precipitation, which finally define the magnitude, rate and direction of the SOC changes. We estimated a global SOC stock in the top 30 cm of around 793 Pg with annual losses due to landcover change of 1.9 Pg SOC yr−1 from 2001 to 2020, 20% larger than the annual production-based emissions of the United States in 2018. The biggest losses were found in the tropic and sub-tropical regions, accounting for almost 50% of the total global loss. This is a considerable contribution to greenhouse gas emissions but it also has a direct impact on agricultural production with more than 16 million hectares yr−1 falling below critical SOC limits. The proposed modelling framework is flexible, allowing it to be updated as more remote sensing and soil data becomes available, offering a first-of-its-kind global spatio-temporal SOC stock assessment and monitoring system.

Functional composition of plant communities mediates biomass effects on ecosystem service recovery across an experimental dryland restoration network

Abstract Land degradation can result in a loss of critical ecosystem services that we often seek to restore through re‐establishment of desired plant communities. Trait‐based approaches have the potential to target specific ecosystem services based on associations between the functional composition of plant communities and ecosystem properties that serve as indicators of those services. The effect of functional composition on ecosystem recovery may depend on the amount of restored plant biomass, itself a supporting service frequently targeted in restoration efforts. Yet, interactions between functional composition and biomass are not formally integrated into trait‐based analytical frameworks. We tested the hypothesis that functional composition of plant communities both drives, and interacts with, biomass production to influence indicators of soil functioning and weed suppression across a network of degraded dryland restoration experiments. This networked approach allowed us to identify generalized effects of functional composition on ecosystem recovery across a range of dryland climate conditions. Climate had a substantial effect on ecosystem indicators, with weed cover and soil surface stability increasing in more arid climates, water infiltration increasing with precipitation, and aggregate structure increasing with less freezing. After accounting for climate effects across study sites, we found significant effects of community‐weighted mean (CWM) trait values on biomass, particularly a positive effect of leaf carbon‐to‐nitrogen ratio, and of CWM‐biomass interactions on other ecosystem indicators. Cover of exotic species was reduced in restored communities with a combination of low leaf dry matter content and high biomass, soil water infiltration increased with lower specific root length and high biomass, and soil aggregate stability increased with higher root dry matter content and high biomass, among other effects. Functional diversity had no significant effects on any ecosystem indicators. Synthesis: The influence of community functional composition on ecosystem properties increases with community biomass, particularly in disturbed or low productivity systems. This suggests that active management should not only focus on trait values that optimize individual ecosystem indicators but also how those functional strategies are complementary or counter to those that increase biomass. Read the free Plain Language Summary for this article on the Journal blog

Soil enzymes as indicators of soil function: A step toward greater realism in microbial ecological modeling.

Soil carbon (C) and nitrogen (N) cycles and their complex responses to environmental changes have received increasing attention. However, large uncertainties in model predictions remain, partially due to the lack of explicit representation and parameterization of microbial processes. One great challenge is to effectively integrate rich microbial functional traits into ecosystem modeling for better predictions. Here, using soil enzymes as indicators of soil function, we developed a competitive dynamic enzyme allocation scheme and detailed enzyme-mediated soil inorganic N processes in the Microbial-ENzyme Decomposition (MEND) model. We conducted a rigorous calibration and validation of MEND with diverse soil C-N fluxes, microbial C:N ratios, and functional gene abundances from a 12-year CO2 ×N grassland experiment (BioCON) in Minnesota, USA. In addition to accurately simulating soil CO2 fluxes and multiple N variables, the model correctly predicted microbial C:N ratios and their negative response to enriched N supply. Model validation further showed that, compared to the changes in simulated enzyme concentrations and decomposition rates, the changes in simulated activities of eight C-N-associated enzymes were better explained by the measured gene abundances in responses to elevated atmospheric CO2 concentration. Our results demonstrated that using enzymes as indicators of soil function and validating model predictions with functional gene abundances in ecosystem modeling can provide a basis for testing hypotheses about microbially mediated biogeochemical processes in response to environmental changes. Further development and applications of the modeling framework presented here will enable microbial ecologists to address ecosystem-level questions beyond empirical observations, toward more predictive understanding, an ultimate goal of microbial ecology.

Impacts of reducing fallow periods on indicators of soil function in subtropical dryland farming systems

Seasonal fallows – periods with no living plant cover – are frequently implemented in dryland cropping systems to allow recharge of soil moisture for the subsequent cash crop. Over time, repeated fallow periods deplete soil organic matter, a foundation of soil health that affects the long-term functional capacity of soils. Reducing fallow periods by growing cover crops (non-harvested crops terminated prior to reproductive development), double cropping (increasing the frequency of harvested crops), or rotating to ley pasture for several years, were investigated for their potential to improve or maintain soil functional attributes. These ‘reduced fallow’ systems were compared against a conventional cereal-based production system with seasonal fallows as well as against a permanent fallow. Soil in the reduced fallow systems had higher concentrations of total nitrogen and mineral-associated nitrogen compared with the conventional system and permanent fallow. Reduced fallow systems also had higher concentrations of total organic carbon and mineral-associated carbon than the permanent fallow, but not the conventional system. These changes were associated with greater soil microbial respiration and improved surface soil moisture storage at cash crop planting. The conventional, cover crop and ley pasture systems had similar soil structure with greater abundance of mega-aggregates. In contrast, the double crop system had greater abundance of micro- and macro-aggregates as did the ley pasture systems that were subject to tillage after three years in preparation for a return to cropping. The ley pasture also had substantially greater numbers of root-lesion nematodes (Pratylenchus thornei), surpassing the 2000 nematodes kg-1 threshold for economic damage. The results demonstrate that different methods for reducing fallow periods can generate a range of outcomes that are not uniformly desirable in terms of soil functional attributes. Across the indicators assessed, the cover crop system generated the widest range of improvements in soil fertility and function compared with the conventional system. This suggests cover cropping may be a valuable tool for promoting soil health in subtropical dryland farming systems.

Impact of Cover Crop Monocultures and Mixtures on Organic Carbon Contents of Soil Aggregates

Cover crops are considered an integral component of agroecosystems because of their positive impacts on biotic and abiotic indicators of soil health. At present, we know little about the impact of cover crop types and diversity on the organic carbon (OC) contents of different soil aggregate-size classes. In this study, we investigated the effect of cover plant diversity on OC contents of different soil aggregates, such as macro- (<2000–500 μm), meso- (<500–250 μm), and micro-aggregates (<250 μm). Our experiment included a total of 12 experimental treatments in triplicate; six different monoculture treatments such as chickling vetch (Vicia villosa), crimson clover (Trifolium incarnatum), hairy vetch (Vicia villosa), field peas (Pisum sativum), oilseed radish (Raphanus sativus), and mighty mustard (Brassica juncea), and their three- and six-species mixture treatments, including one unplanted control treatment. We performed this experiment usingdeep pots that contained soil collected from a corn-soybean rotation field. At vegetative maturity of cover plants (about 70 days), we took soil samples, and the soil aggregate-size classes were separated by the dry sieving. We hypothesized that cover crop type and diversity will improve OC contents of different soil aggregate-size classes. We found that cover plant species richness weakly positively increased OC contents of soil macro-aggregates (p = 0.056), whereas other aggregate-size classes did not respond to cover crop diversity gradient. Similarly, the OC contents of macroaggregates varied significantly (p = 0.013) under cover crop treatments, though neither monoculture nor mixture treatments showed significantly higher OC contents than the control treatment in this short-term experiment. Interestingly, the inclusion of hairy vetch and oilseed radish increased and decreased the OC contents of macro- and micro-aggregates, respectively. Moreover, we found a positive correlation between shoot biomass and OC contents of macroaggregates. Overall, our results suggest that species-rich rather than -poor communities may improve OC contents of soil macroaggregates, which constitute a major portion of soil systems, and are also considered as important indicators of soil functions.

Establishing reference values for soil microbial biomass-C in agroecosystems in the Atlantic Forest Biome in Southern Brazil

Abstract Soil microbial biomass plays a key role in the biogeochemical cycles, degradation of organic pollutants and soil aggregation, and its estimation through soil microbial biomass-C (MB-C) is often referred as a potential indicator of soil functioning. This study aimed to identify reference values of MB-C that would relate to crop yield. Soybean and maize grain yields and microbial biomass-C (MB-C) data were gathered from studies listed in “Web of Science” performed in agroecosystems located in the Atlantic Forest Biome in Southern Brazil. Database was composed by 78 datasets, where soil samplings for evaluation of MB-C were performed at the 0–10 cm layer at flowering stage, and evaluated by the fumigation-extraction method. A meta-regression using the Mitscherlich model was applied to determine the MB-C reference value corresponding to 80% of maximum yield. The effects of soil management systems and crop systems were verified by comparing the confidence intervals. Soil tillage decreased MB-C and yield, while crop rotation increased yield but not MB-C. It was not possible to find a reference value for soybean, because of the variability not explainable by the MB-C. The reference value related to high maize yield (>6,752 kg ha−1) was of 170 μg C g−1 soil, but further results must be included to decrease the variability.

The effect of forest degradation intensity on soil function indicators in northern Iran

The degradation of forest ecosystems has an important role in global warming through the carbon (C) and nitrogen (N) cycles. The response of soil organic matter fractions and microbial activities to forest degradation has been poorly studied. The purpose of the current research was to evaluate the effect of different intensities (i.e. low, moderate, and high) of forest degradation in northern Iran on the fractions of particulate and dissolved organic matter, microbial and enzyme activities as indicators of soil function. In this research, a total of 15 soil samples (30 × 30 × 10 cm) from each studied forest sites were transferred to the laboratory. Fifty-two soil characteristics of those forest ecosystems were studied by principal component analysis (PCA), with an explanation of more than 55% of the variance by axes 1 and 2. The fractions of soil organic matter (particulate and dissolved organic matter), fertility, microbial activities (microbial respiration and microbial biomass of carbon, nitrogen, and phosphorous), enzyme indices (urease, acid phosphatase, arylsulfatase, invertase, geometric mean of enzyme activities, and Shannon’s diversity index), and stoichiometry of enzyme activity/organic C were enhanced at sites with low degradation intensity. Instead, all studied soil characteristics were suppressed at sites showing high forest degradation. The stoichiometry of enzyme activity/microbial biomass of C were not significantly different among the studied stands. It was concluded that the degradation intensity of natural forests can play a very important role in the soil function of temperate ecosystems.

Microbiological indicators of soil quality are related to greater coffee yield in the Brazilian Cerrado region

Abstract One of the main challenges faced by the rapidly growing human population is to increase agricultural sustainability. Soil quality is an essential aspect of agricultural sustainability, but farmers have generally assessed this based on conventional chemical and physical indicators, with little application of indicators of soil functions, such as soil microbiological attributes. These indicators may respond faster to changes in soil conditions and thus they could correlate better with the growth/yield of crops such as coffee. The aim of this study was to investigate the potential of soil microbiological indicators in assessment of soil quality for sustained coffee production, compared to or combined with conventional soil physical and chemical indicators. To accomplish that, two observational studies were performed by measuring soil microbiological, physical, and chemical attributes in coffee field areas with contrasting records of coffee yield but under similar edaphic and climatic conditions in the Cerrado (Brazilian tropical savanna) region of Minas Gerais, Brazil. In the first study, two neighboring field areas with contrasting yield were selected for each of the following three cultivars: Catuai Vermelho IAC 99, Catuai Vermelho IAC 144, and Rubi MG 1192. Samples were taken in two seasons (dry and rainy) of the year. In the second study, four neighboring field areas cropped with the cultivar Catuai Vermelho IAC 144 were chosen based on their contrasting yield records. In both studies, the experimental procedure consisted of collecting four composite soil samples (each composed of four subsamples) taken at a depth of 0–10 cm from each field area within the area of canopy projection of the coffee plant. The microbiological attributes evaluated were microbial biomass carbon; microbial basal respiration; metabolic quotient; urease, β-glucosidase, and arylsulfatase enzyme activities; and fluorescein diacetate hydrolysis. The physical and chemical attributes evaluated were texture, pH, organic matter content, and fertility. Climatic conditions affected the responses and must be considered in evaluation and elaboration of soil quality indexes. The physical and chemical attributes that were most closely related to higher coffee yields were Ca contents, organic matter content, effective cation exchange capacity, and base saturation in both studies in the rainy season. Microbial biomass carbon, metabolic quotient, and β-glucosidase and urease activities were positively related to higher coffee yields, and these attributes exhibited greater ability to discriminate the production potential of the soil than chemical and physical attributes did, in both seasons and studies.

Novel soil quality indicators for the evaluation of agricultural management practices: a biological perspective

Developments in soil biology and in methods to characterize soil organic carbon can potentially deliver novel soil quality indicators that can help identify management practices able to sustain soil productivity and environmental resilience. This work aimed at synthesizing results regarding the suitability of a range of soil biological and biochemical properties as novel soil quality indicators for agricultural management. The soil properties, selected through a published literature review, comprised different labile organic carbon fractions [hydrophilic dissolved organic carbon, dissolved organic carbon, permanganate oxidizable carbon (POXC), hot water extractable carbon and particulate organic matter carbon], soil disease suppressiveness measured using a <i>Pythium</i>-<i>Lepidium</i> bioassay, nematode communities characterized by amplicon sequencing and qPCR, and microbial community level physiological profiling measured with MicroResp^TM. Prior studies tested the sensitivity of each of the novel indicators to tillage and organic matter addition in ten European long-term field experiments (LTEs) and assessed their relationships with pre-existing soil quality indicators of soil functioning. Here, the results of these previous studies are brought together and interpreted relative to each other and to the broader body of literature on soil quality assessment. Reduced tillage increased carbon availability, disease suppressiveness, nematode richness and diversity, the stability and maturity of the food web, and microbial activity and functional diversity. Organic matter addition played a weaker role in enhancing soil quality, possibly due to the range of composition of the organic matter inputs used in the LTEs. POXC was the indicator that discriminated best between soil management practices, followed by nematode indices based on functional characteristics. Structural equation modeling shows that POXC has a central role in nutrient retention/supply, carbon sequestration, biodiversity conservation, erosion control and disease regulation/suppression. The novel indicators proposed here have great potential to improve existing soil quality assessment schemes. Their feasibility of application is discussed and needs for future research are outlined.

Reducing soil erosion in smallholder farming systems in east Africa through the introduction of different crop types

AbstractOn low-input smallholder farms of Kenyan upland landscapes, erosion of nutrient-rich topsoil strongly affects crop yields. Where maize (Zea mays) is intercropped on erosion-prone slopes, intercropping can potentially reduce soil erosion. The objective of this research was to quantify the contribution of crops and crop mixtures of different growth habits to erosion control and their influence on above-ground biomass and earthworm abundance as indicators of soil function in smallholder farming systems under a bimodal rainfall pattern in Western Kenya. The experiment involved five treatments, namely maize (Z. mays)/common bean (Phaseolus vulgaris) intercrop (maize intercrop), maize/common bean intercrop plus Calliandra (Calliandra calothyrsus) hedgerows and Calliandra mulch (Calliandra), sole Lablab (Lablab purpureus), sole Mucuna (Mucuna pruriens) and groundnut (Arachis hypogaea) intercropped with maize (during the short rains). The experiment was conducted over three consecutive cropping seasons and the cropping system had significant effects on soil loss, runoff, water infiltration, earthworm abundance and above-ground biomass and crop grain yield. The Calliandra treatment had the lowest runoff (11.6–17.2 mm ha−1) and soil erosion (31–446 kg ha−1 per season) in all the seasons, followed by the Mucuna treatment. Lablab was affected by disease and showed the highest soil erosion in the last two seasons. Infiltration was highest in Calliandra treatment, and earthworm abundance was higher under Mucuna and Calliandra treatments (229 and 165 earthworms per square metre, respectively) than under other crops. Our results suggest that including sole crops of herbaceous species such as Mucuna, or tree hedgerows with mixtures of maize and grain legumes has the potential to reduce runoff and soil erosion in smallholder farming. Additionally, these species provide a suitable habitat for earthworms which stabilise soil structure and macropores and thus potentially increase infiltration, further reducing soil erosion.

Earthworms Mitigate Pesticide Effects on Soil Microbial Activities.

Earthworms act synergistically with microorganisms in soils. They are ecosystem engineers involved in soil organic matter degradation and nutrient cycling, leading to the modulation of resource availability for all soil organisms. Using a soil microcosm approach, we aimed to assess the influence of the earthworm Aporrectodea caliginosa on the response of soil microbial activities against two fungicides, i.e., Cuprafor Micro® (copper oxychloride, a metal) and Swing® Gold (epoxiconazole and dimoxystrobin, synthetic organic compounds). The potential nitrification activity (PNA) and soil enzyme activities (glucosidase, phosphatase, arylamidase, and urease) involved in biogeochemical cycling were measured at the end of the incubation period, together with earthworm biomass. Two common indices of the soil biochemistry were used to aggregate the response of the soil microbial functioning: the geometric mean (Gmean) and the Soil Quality Index (SQI). At the end of the experiment, the earthworm biomass was not impacted by the fungicide treatments. Overall, in the earthworm-free soil microcosms, the two fungicides significantly increased several soil enzyme and nitrification activities, leading to a higher GMean index as compared to the non-treated control soils. The microbial activity responses depended on the type of activity (nitrification was the most sensitive one), on the fungicide (Swing® Gold or Cuprafor Micro®), and on the doses. The SQI indices revealed higher effects of both fungicides on the soil microbial activity in the absence of earthworms. The presence of earthworms enhanced all soil microbial activities in both the control and fungicide-contaminated soils. Moreover, the magnitude of the fungicide impact, integrated through the SQI index, was mitigated by the presence of earthworms, conferring a higher stability of microbial functional diversity. Our results highlight the importance of biotic interactions in the response of indicators of soil functioning (i.e., microbial activity) to pesticides.

Application of oil palm empty fruit bunch effects on soil biota and functions: A case study in Sumatra, Indonesia

Oil palm (Elaeis guineensis) is an important tropical crop which provides one-fifth of the world’s vegetable oil, yet its rapid expansion can negatively influence the soil ecosystem. Identifying suitable agronomic management such as crop residue application is important for the sustainable development of oil palm. We examined the effects of adding empty fruit bunches (EFB), a major oil palm residue, on multiple soil abiotic properties, soil biota, and indicators of soil functions. We compared treatments of EFB applications with three application rates, and a chemical fertilizer treatment in a 15–year trial in Central Sumatra, Indonesia. EFB application increased pH and aggregate stability in 0–10 cm soils and decreased the soil bulk density. EFB application increased the abundance of soil detritivore mites, soil fauna feeding activity, and soil microbial activity. EFB application decreased the biomass of a dominant invasive earthworm species, Pontoscolex corethrurus (Müller, 1857). Results from structural equation modelling suggested that EFB directly affected soil biota and functions, rather than through altering soil abiotic properties. The effects of EFB application on most soil abiotic properties, soil biota and function indicators were independent of the application rate. Our results revealed that EFB application has a high potential to enhance soil biota and functions in oil palm plantations.

Evaluation of Soil Function Following Remediation of Petroleum Hydrocarbons—a Review of Current Remediation Techniques

Management of lands contaminated by petroleum hydrocarbons (PHC) continues to evolve, as project goals may be shifting from contaminant reduction to ecosystem restoration. Restoring soil function is vital to overall ecosystem recovery, as soils perform numerous processes that are inhibited by PHC contamination. The purpose of this review is to summarize the effects of various remediation strategies on soil properties and evaluate how those effects relate to soil functions. All remediation techniques alter soil function, and the extent of alteration is based on project-specific operational parameters. Broadly, most techniques alter soil organic matter (SOM) content and soil pH, which are important variables associated with many soil processes. Additionally, recent technological advances have made the characterization of soil microbial communities and activities more accessible, so the field continues to gain knowledge on how remediation strategies affect soil microorganisms that are vital in nutrient cycling and waste management. This review identified soil properties and functions that are likely to be affected by each strategy and that should be monitored following successful remediation. The extent of changes in soil properties is dictated by specific implementation of remediation methods, so general comparisons between methods may not be appropriate. While important variables like SOM and pH are valuable indicators of soil function, the dynamic relationships between all soil properties should not be overlooked following soil remediation. Thus, future research on soil remediation should strive to assess changes in how soils function, in addition to contaminant removal efficiency.

Cover cropping and no-tillage improve soil health in an arid irrigated cropping system in California’s San Joaquin Valley, USA

The concept of soil health has attracted considerable attention during the past two decades, but few studies have focused on the effects on soil health of long-term soil management in arid irrigated environments. We investigated the effects of cover cropping and no-till management on soil physical and chemical properties during a 15-year experiment in California’s San Joaquin Valley (SJV) USA. Our objective was to determine if soil health could be improved by these practices in an annual crop rotation. The impact of long-term no-tillage (NT) and cover cropping (CC) practices, alone and in combination, was measured and compared with standard tillage (ST) with and without cover crops (NO) in irrigated row crops after 15 years of management. Soil aggregation, rates of water infiltration, content of carbon, nitrogen, water extractable organic carbon (WEOC) and organic nitrogen (WEON), residue cover, and biological activity were all increased by NT and CC practices relative to STNO. However, effects varied by depth with NT increasing soil bulk density by 12% in the 0–15cm depth and 10% in the 15–30cm depth. Higher levels of WEOC were found in the CC surface (0–5cm) depth in both spring and fall samplings in 2014. Surface layer (0–15cm) WEON was higher in the CC systems for both samplings. Tillage did not affect WEON in the spring, but WEON was increased in the NT surface soil layer in the fall. Sampling depth, CC, and tillage affected 1-day soil respiration and a soil health index assessment, however the effects were seasonal, with higher levels found in the fall sampling than in the spring. Both respiration and the soil health index were increased by CC with higher levels found in the 0–5cm depth than in the 5–15 and 15–30cm depths. Results indicated that adoption of NT and CC in arid, irrigated cropping systems could benefit soil health by improving chemical, physical, and biological indicators of soil functions while maintaining similar crop yields as the ST system.

Soil microbial community structure and function are significantly affected by long-term organic and mineral fertilization regimes in the North China Plain

An improved understanding of the complex interactions and relationships in the soil ecosystem is essential to predict the impact of farming practices on soil quality and its capacity for agricultural production. This study aims to improve our understanding of the impacts of fertilization strategy on key indicators of soil biological and chemical quality. We studied soils from a winter wheat-summer maize rotational experiment in the North China Plain with six different fertility treatments: no amendments (CK); standard mineral fertilizer treatment (SMF) or standard organic manure treatment (SMA) reflecting local farmer practice; mixed treatment with fertilizer and manure at half the rates for the SMF and SMA treatments (1/2 SMF+1/2 SMA); double mineral fertilizer treatment (DMF); and double organic manure treatment (DMA). Soil organic C (SOC), total N (TN), total P (TP), pH, and dissolved organic C (DOC) and N (DON) and microbial biomass C (Cmic) and N (Nmic) were determined using standard methods. Soil bacterial community structure was assessed by denaturing gradient gel electrophoresis (DGGE), and activities for 10 extracellular enzymes (EEAs) were measured as indicators of soil function. Repeated application of either organic manure or mineral fertilizer increased SOC, TN, TP, DOC, DON, Cmic and Nmic, and decreased soil pH. Higher rates of organic manure fertilization significantly affected soil chemical properties compared to the lower rate. Soil bacterial community structure was significantly altered by the long-term fertilization regimes and diversity was significantly higher in the double manure rate treatment relative to mineral fertilizer. The higher urease, α-glycosidase, N-acetyl-β-glucosaminidase, l-leucine aminopeptidase (involved in N cycling), β-glucosidase, β-xylosidase and β-cellobiosidase (involved in C cycling), and alkaline phosphatase (involved in P cycling) activities for organic manure fertilized soils reflected a higher nutrient cycling capacity compared to mineral fertilized and control plots. Soil bacterial community diversities increased with Cmic and variations in EEAs were strongly correlated with soil DOC availability. Our study has demonstrated that a long-term fertilization strategy can be used to improve soil quality. Clearly, the use of organic fertilizers where available, is a win–win strategy for maintaining soil quality and crop productivity, while ensuring the delivery of soil ecosystem services into the future.

Changes in Soil Microbial Biomass and Residual Indices as Ecological Indicators of Land Use Change in Temperate Permanent Grassland

The relationship between microbial biomass, residues and their contribution to microbial turnover is important to understand ecosystem C storage. The effects of permanent grassland (100 % ryegrass--PG), conversion to modified grassland (mixture of grass and clover--MG) or maize monoculture (MM) on the dynamics of soil organic C (SOC), microbial biomass, fungal ergosterol and microbial residues (bacterial muramic acid and fungal glucosamine) were investigated. Cattle slurry was applied to quantify the effects of fertilisation on microbial residues and functional diversity of microbial community across land use types. Slurry application significantly increased the stocks of microbial biomass C and S and especially led to a shift in microbial residues towards bacterial tissue. The MM treatment decreased the stocks of SOC, microbial biomass C, N and S and microbial residues compared with the PG and MG treatments at 0-40 cm depth. The MM treatment led to a greater accumulation of saprotrophic fungi, as indicated by the higher ergosterol-to-microbial biomass C ratio and lower microbial biomass C/S ratio compared with the grassland treatments. The absence of a white clover population in the PG treatment caused a greater accumulation of fungal residues (presumably arbuscular mycorrhizal fungi (AMF), which do not contain ergosterol but glucosamine), as indicated by the significantly higher fungal C-to-bacterial C ratio and lower ergosterol-to-microbial biomass C ratio compared with the MG treatment. In addition to these microbial biomass and residual indices, the community level physiological profiles (CLPP) demonstrated distinct differences between the PG and MG treatments, suggesting the potential of these measurements to act as an integrative indicator of soil functioning.

Indicators and trade-offs of ecosystem services in agricultural soils along a landscape heterogeneity gradient

Soil functions can be classified as supporting (nutrient cycling) and provisioning (crop production) ecosystem services (ES). These services consist of multiple and dynamic functions and are typically assessed using indicators, e.g. microbial biomass as an indicator of supporting services. Agricultural intensification negatively affects indicators of soil functions and is therefore considered to deplete soil ES. It has been suggested that incorporating leys into crop rotations can enhance soil ES. We examined this by comparing indicators of supporting soil services – organic carbon, nitrogen, water holding capacity and available phosphorous (carbon storage and nutrient retention); net nitrogen mineralisation rate and microbial biomass (nutrient cycling and retention) – in barley fields, leys and permanent pastures along a landscape heterogeneity gradient (100, 500 and 1000m radii). In addition, barley yields (provisioning service) were analysed against these indicators to identify trade-offs among soil services. Levels of most indicators did not differ between barley and ley fields and were consistently lower than in permanent pastures. Leys supported greater microbial biomass than barley fields. Landscape heterogeneity had no effect on the indicators or microbial community composition. However, landscape heterogeneity correlated negatively with yield and soil pH, suggesting that soils in heterogeneous landscapes are less fertile and therefore have lower yields. No trade-offs were found between increasing barley yield and the soil indicators. The results suggest that soil ES are determined at the field level, with little influence from the surrounding landscape, and that greater crop yields do not necessarily come at the expense of supporting soil services.

Effect of EDTA washing of metal polluted garden soils. Part I: Toxicity hazards and impact on soil properties

We applied a multi-level approach assessing the quality, toxicity and functioning of Pb, Zn and Cd contaminated/remediated soil from a vegetable garden in Meza Valley, Slovenia. Contaminated soil was extracted with EDTA and placed into field experimental plots equipped with lysimeters. Soil properties were assessed by standard pedological analysis. Fractionation and leachability of toxic metals were analyzed by sequential extraction and TCLP and metal bioaccessibility by UBM tests. Soil respiration and enzyme activities were measured as indicators of soil functioning. Remediation reduced the metal burden by 80, 28 and 72% for Pb, Zn and Cd respectively, with a limited impact on soil pedology. Toxic metals associated with labile soil fractions were largely removed. No shifts between labile and residual fractions were observed during the seven months of the experiment. Initial metal leaching measured through lysimeters eventually ceased. However, remediation significantly diminished potential soil enzyme activity and no trends were observed of the remediated soil recovering its biological properties. Soil washing successfully removed available forms of Pb, Zn and Cd and thus lowered the human and environmental hazards of the remediated soil; however, remediation also extracted the trace elements essential for soil biota. In addition to reduced water holding capacity, soil health was not completely restored.