Search

Environmental stress is the main cause of the decline of species diversity in low-productive fen meadows in the Netherlands. Attempts to restore species diverse fen meadows e.g. by sod cutting frequently fail. We supposed that unsuccessful efforts are due to ignoring the impact of environmental stress on the performance of soil biota, which play a key role in N-immobilization and keeping available-N for primary production low. We investigated both pristine and degraded natural sites and successfully and unsuccessfully restored sites of poor and rich fen meadows. We determined plant species composition, soil chemical properties, N-pools in soil biota, N-mineralization rates, and N-fluxes. In pristine rich and poor fen meadows, mineral-N was poorly available for primary production due to a strong N-immobilization by soil biota. Annual N-immobilization fluxes exceeded by far the annual N-harvest by primary production. N-immobilization in pristine fens was higher than in degraded fens. In successfully restored rich fens, net N-mineralization was lower and N-immobilization higher than in the unsuccessful category. From our results, we derived the hypothesis that in degraded or in unsuccessfully restored fens the soils internal N-balance shifted from N-immobilization to net N-mineralization, favoring biomass production but disadvantaging plant species diversity. N-retention driven by an active N-immobilizing soil biological community, is likely a decisive process for successful recovery of plant species diversity in low productive fen meadows. We recommend that restoration techniques should stimulate a functionally diverse soil fauna, as this may enhance the storage of available nutrients in the soil food web. [ABSTRACT FROM AUTHOR]

Microorganisms respond rapidly to changing environmental conditions. Therefore microbes are generally considered as sensitive indicators of soil health. The aim of this study was to assess the biological fertility status and sustainability of three differently managed agricultural soils by using microbial indicators. Management practices involved a soil with minimum treatment (biodynamic); a soil characterized by periodic application of manure and chemical fertilizer (manure); and a soil characterized by depurated and stabilized organic sludge amendment (sludge). Samples were taken four times during a year, at two depths: 0-15 and 15-30 cm. An extensive characterization of soil organic matter was carried out. Biochemical parameters included metabolic quotient, mineralization quotient and kinetic parameters of microbial decomposition of soil organic matter. Community level physiological profile analysis (CLPP) was used to investigate soil microbial energetic strategies adopted in differently managed soils. Total amounts of fungi and bacteria were determined by direct microscopy. Indicators related to labile and humic organic matter fractions suggest significantly lower soil fertility and lower sustainability in the sludge amended treatment. Differences between the biodynamic treatment and Manure treatment were less consistent. Eco-physiological quotients and kinetic parameters of C-mineralization indicated a steady state in the biodynamic treatment and stressed conditions in the sludge treatment. Microbial communities seem to adopt a typically K-strategy (persistent) in the bio-dynamic treatment and a typically r-strategy (opportunists) in the sludge treatment. Manure management shows an intermediate result: the superficial layer is characterized by r-strategists and the deeper layer by K-strategists. [ABSTRACT FROM AUTHOR]

In three dairy grasslands on peat, minerals were added to manipulate the soil Ca:Mg ratio with or without effect on pH. The responses of soil properties and grass N yield were measured. CaCO3 application led to higher soil Ca:Mg ratio and pHKCl compared to the untreated control, decreased Ntotal and Ctotal, and increased P availability. Grass N yield increased in the first year by only 6% of the reduction in soil Ntotal, but not in the second year. A higher pH increased SOM decomposition, especially in soils with high P availability. MgCO3 reduced the Ca:Mg ratio, had little influence on soil parameters and no effect on grass N yield. In contrast, CaSO4 and MgSO4 did not influence pHKCl but reduced grass N yield in most cases. Results suggest stabilisation of organic matter by Ca binding in treatments with added Ca. We conclude that grass N yield was not linked with changes in Ca:Mg ratio but with soil pH. The pH effects on SOM decomposition depended on P availability and Ca binding. Hence, to avoid potentially large soil losses of C and N, the current agricultural advice on pH management in peat grasslands should be better adapted to local edaphic characteristics. [ABSTRACT FROM AUTHOR]

Understanding the impacts of agricultural intensification and extensification on soil biota communities is useful in order to preserve and restore biological diversity in agricultural soils and enhance the role of soil biota in agroecosystem functioning. Over four consecutive years, we investigated the effects of agricultural intensification and extensification (including conversion of grassland to arable land and vice versa, increased and decreased levels of mineral fertilization, and monoculture compared to crop rotation) on-major soil biota group abundances and functional diversity. We integrated and compared effects across taxonomic levels to identify sensitive species groups. Conversion of grassland to arable land negatively affected both abundances and functional diversity of soil biota. Further intensification of the cropping system by increased fertilization and reduced crop diversity exerted smaller and differential effects on different soil biota groups. Agricultural intensification affected abundances of taxonomic groups with larger body size (earthworms, enchytraeids, microarthropods, and nematodes) more negatively than smaller-sized taxonomic groups (protozoans, bacteria, and fungi). Also functional group diversity and composition were more negatively affected in larger-sized soil biota (earthworms, predatory mites) than in smaller-sized soil biota (nematodes). Furthermore, larger soil biota appeared to be primarily affected by short-term consequences of conversion (disturbance, loss of habitat), whereas smaller soil biota were predominantly affected by long-term consequences (probably loss of organic matter). Reestablishment of grassland resulted in increased abundances of soil biota groups, but since not all groups increased in the same measure, the community structure was not completely restored. We concluded that larger-sized-soil biota are more sensitive to agricultural intensification than smaller-sized soil biota. Furthermore, since larger-sized soil biota groups had lower taxonomic richness, we suggest that agricultural intensification exerts strongest effects on species-poor soil biota groups, thus supporting the hypothesis that biodiversity has an "insurance" function. As soil biota play an important role in agroecosystem functioning, altered soil biota abundances and functional group composition under agricultural intensification are likely to affect the functioning of the agroecosystem. [ABSTRACT FROM AUTHOR]

In order to study the soil aggregate distributions and soil organic matter (SOM), we sampled top- and subsoils in four intensively farmed croplands (two organic (Org-OB and Org-LA), and two conventional (Con-OB and Con-LA)) on Haplic Chernozems located in Marchfeld in the east of Vienna (Austria). Soil structure and SOM quantity, quality and distribution between free and occluded particulate organic matter and aggregate size fractions (<20 µm, 20-250 µm, 250-5000 µm) were studied by following a density fractionation procedure with low-energy ultrasound treatment. The relation of the soil physicochemical (e.g., particle size distribution, pH, organic carbon, total nitrogen) and biological properties (e.g., fungal biomass, active fungi) with stable soil aggregate size fractions and SOM was studied. The mean weight diameter (MWD) showed no significant difference between all studied sites and was between 3.8 mm and 10.0 mm in topsoils and between 6.7 mm and 11.9 mm in subsoils. In topsoils, the contents of calcium-acetate-lactate (CAL)-extractable P, active fungal biomass, dithionite-extractable Fe and sand were significantly positively correlated with the amount of the macroaggregates and with the MWD. We observed that most soil organic carbon, depending on soil texture, was stored in the microaggregate size classes <20 µm and 20-250 µm. [ABSTRACT FROM AUTHOR]

Intensive agricultural crop production can lead to a decline in biological soil characteristics and functions, such as soil microbial biomass and activity, carbon and nutrient cycling and soil suppressiveness, important for the sustainable production of food and feed. There is a need to understand how those soil functions can be improved by agricultural practices. In a long-term field study, we assessed whether reduced tillage could enhance soil biological parameters and soil suppressiveness against the plant-pathogenic fungus Rhizoctonia solani AG2-2IIIB and bacterium Streptomyces scabies. Soil suppressiveness was assessed in bioassays with a susceptible crop while adding pathogen inoculum. Undisturbed soil cores (0–12 cm) were used in these bioassays to include the soil structural aspects, which were likely affected by the tillage treatments. Reduced i.e., non-inversion, tillage was compared with conventional ploughing treatment over 6 years. We found that reduced tillage led to an increase in bacterial and fungal biomass, labile carbon and nitrogen and an increase in the abundance of potential bacterial antagonists, compared to conventional tillage in the upper 12 cm. However, the increase of these microbial parameters did not lead to consistent changes in soil suppressiveness against both R. solani and S. scabies in response to the tillage treatment. Rather, disease suppressiveness varied significantly between field and year of sampling but was not correlated to any of the assessed soil parameters. Thus while reduced tillage can be beneficial for soil biology, other measures will have to be investigated for inducing R. solani and S. scabies disease suppressiveness. • Reduced tillage led to a rapid increase in microbial biomass in the 12-cm upper soil layer • Abundance of potentially beneficial bacteria Lysobacter and Streptomyces increased as well under reduced tillage • Reduced tillage did not affect suppressiveness against Rhizoctonia solani AG2-2IIIB or Streptomyces scabies in bioassays • These bioassays were performed in undisturbed soil columns with a model crop and artificial pathogen inoculation. [ABSTRACT FROM AUTHOR]

Abstract: Growth in human population and demand for wealth creates ever-increasing pressure on global soils, leading to soil losses and degradation worldwide. Critical Zone science studies the impact linkages between these pressures, the resulting environmental state of soils, and potential interventions to protect soil and reverse degradation. New research on soil processes is being driven by the scientific hypothesis that soil processes can be described along a life cycle of soil development. This begins with formation of new soil from parent material, development of the soil profile, and potential loss of the developed soil functions and the soil itself under overly intensive anthropogenic land use, thus closing the cycle. Four Critical Zone Observatories in Europe have been selected focusing research at sites that represent key stages along the hypothetical soil life cycle; incipient soil formation, productive use of soil for farming and forestry, and decline of soil due to longstanding intensive agriculture. Initial results from the research show that soil develops important biogeochemical properties on the time scale of decades and that soil carbon and the development of favourable soil structure takes place over similar time scales. A new mathematical model of soil aggregate formation and degradation predicts that set-aside land at the most degraded site studied can develop substantially improved soil structure with the accumulation of soil carbon over a period of several years. Further results demonstrate the rapid dynamics of soil carbon; how quickly it can be lost, and also demonstrate how data from the CZOs can be used to determine parameter values for models at catchment scale. A structure for a new integrated Critical Zone model is proposed that combines process descriptions of carbon and nutrient flows, a simplified description of the soil food web, and reactive transport; all coupled with a dynamic model for soil structure and soil aggregation. This approach is proposed as a methodology to analyse data along the soil life cycle and test how soil processes and rates vary within, and between, the CZOs representing different life cycle stages. In addition, frameworks are discussed that will help to communicate the results of this science into a more policy relevant format using ecosystem service approaches. [Copyright &y& Elsevier]

Soil is a complex natural resource that is considered non-renewable in policy frameworks, and it plays a key role in maintaining a variety of ecosystem services (ES) and life-sustaining material cycles within the Earth's Critical Zone (CZ). However, currently, the ability of soil to deliver these services is being drastically reduced in many locations, and global loss of soil ecosystem services is estimated to increase each year as a result of many different threats, such as erosion and soil carbon loss. The European Union Thematic Strategy for Soil Protection alerts policy makers of the need to protect soil and proposes measures to mitigate soil degradation. In this context, the European Commission-funded research project on Soil Transformations in European Catchments (SoilTrEC) aims to quantify the processes that deliver soil ecosystem services in the Earth's Critical Zone and to quantify the impacts of environmental change on key soil functions. This is achieved by integrating the research results into decision-support tools and applying methods of economic valuation to soil ecosystem services. In this paper, we provide an overview of the SoilTrEC project, its organization, partnerships and implementation.