Agricultural Management Regimes Research Articles

Low nitrous oxide fluxes from mineral affected peatland soils in Iceland

Nitrous oxide (N2O) is a potent greenhouse gas, and soil is one of its most substantial sources. Emissions are influenced by both biotic and abiotic processes, as well as the physiochemical properties of the medium. Organic soils fully drained in boreal climates are a potentially significant source of nitrous oxide. Lower, drainage levels and nutrient availability have been shown to reduce N2O emissions. Predicting N2O emissions from agriculturally managed peatlands is challenging. In situ measurements are crucial for addressing these difficulties. This study presents three years of in situ field measurements of nitrous oxide fluxes and soil hydrological status in peatland soils under different agricultural management regimes: cultivated drained (CD), uncultivated drained (UCD), and wet (W) in Western Iceland. Fluxes were quantified by analysing a time-concentration series obtained from permanent chambers and subsequently evaluated using gas chromatography in the laboratory. The minimum potential N2O consumption rate (mean ± 95 % Cl) was estimated as 0.76 ± 0.38, 0.56 ± 0.18 and 0.56 ± 0.14 mg N2O-N m⁻² day⁻¹ for CD, UCD, and W sites, respectively. Yearly accumulated emissions were estimated as 2.24 ± 1.47, 1.26 ± 0.64 and 0.26 ± 0.44 kg N2O-N ha−1 yr−1 for CD, UCD, and W sites, respectively. The relatively low emission rates observed at drained sites can be explained by the stable water content, and by limited availability of soil phosphorus, which hampers N2O production and potentially leads to more active N2O consumption. Both the stable water content and low phosphorus availability is explained by mineral inputs to the peatlands, acting through decreased soil unsaturated hydraulic conductivity and increased phosphorus retention. The effects of mineral content offer potential mitigation option to decrease N2O emissions. This study highlights the complexity of N2O emissions from peatland soils and emphasizes the significance of site-specific factors in managing greenhouse gas emissions. Further studies investigating the underlying processes behind N2O fluxes in the peatland and andic soils are recommended.

Soil Microbiomes in Apple Orchards Are Influenced by the Type of Agricultural Management but Never Match the Complexity and Connectivity of a Semi-natural Benchmark.

Conversion of natural ecosystems into agricultural land may strongly affect the soil microbiome and the functioning of the soil ecosystem. Alternative farming systems, such as organic farming, have therefore been advocated to reduce this impact, yet the outcomes of different agricultural management regimes often remain ambiguous and their evaluations mostly lack a proper more natural benchmark. We used high-throughput amplicon sequencing, linear models, redundancy analyses, and co-occurrence network analyses to investigate the effect of organic and integrated pest management (IPM) on soil fungal and bacterial communities in both the crop and drive rows of apple orchards in Belgium, and we included semi-natural grasslands as a benchmark. Fungi were strongly influenced by agricultural management, with lower diversity indices and distinct communities in IPM compared to organic orchards, whereas IPM orchards had a higher AMF abundance and the most complex and connected fungal communities. Bacterial diversity indices, community composition, and functional groups were less affected by management, with only a higher network connectivity and abundance of keystone taxa in organic drive rows. On the other hand, none of the agricultural soil microbiomes matched the complexity and connectedness of our semi-natural benchmark, demonstrating that even more nature-friendly agricultural management practices strongly affect the soil microbiome and highlighting the essential role of (semi-)natural systems as a harbor of robust and functionally diverse fungal and bacterial communities.

Impact of Reduced Rainfall on Above Ground Dry Matter Production of Semi-natural Grassland in South Gloucestershire, UK: A Rainfall Manipulation Study

In the United Kingdom, agricultural grasslands cover 40% of the land area, make up 89% of the total agricultural area and are an important land use for ecosystem services and food security. Climate change predictions suggest that the United Kingdom will experience more frequent and severe periods of drought that may impact these grasslands. As part of the Drought Risk and You (DRY) project, a field experiment in which rain shelters reduced precipitation reaching the vegetation by approximately 50%, was set up in the South West of England. The experiment ran for 3 years, from October 2015 to October 2018. The study was carried out at two locations in the catchment of the Bristol River Frome. Both sites were species-rich semi-natural pastures that had received no inputs of fertilizer or herbicide for many years. Automatic weather stations recorded environmental conditions, especially rainfall, within the experimental area. The existing agricultural management regimes were approximated by cutting the vegetation in the plots, by hand, at the appropriate times of year. The effect of rainfall reduction on plant growth was assessed by biomass sampling. At both sites, the rainfall reduction treatment had only small effects on total above ground dry matter production (biomass). These effects were much smaller than the year-to-year variation in total biomass. Our results suggested that well-established permanent pastures in the South West of England were able to tolerate a 3-year period of reduced water supply. The observed year-to-year variation in biomass demonstrated how important the timing of dry weather is for biomass production, and this will be reflected in effects on yield and quality of hay.

Effects of agricultural management regimes on rotating cropland ecosystem respiration and its components in Southeast China

Investigating ecosystem, soil and aboveground respiration under different agricultural management regimes (i.e., fertilization, crop types and plowing practices) is critical for better understanding the processes of agricultural carbon cycles. The effects of agricultural management regimes on ecosystem respiration and its soil and aboveground respiration components have not been well identified. We performed a field experiment to measure ecosystem and soil respiration under different management regimes. Air temperature, soil temperature, soil moisture, crop growth characteristics [aboveground biomass (AB), leaf biomass (LB), leaf area index (LAI), specific leaf area (SLA), plant height (PH)] and crop productivity indexes [i.e., yield and biomass of a thousand seeds (BTS)] were also measured. The WrP4 treatment, where nitrogen was applied as chemical fertilizer and straw, had significantly (P < 0.05) higher seasonal cumulative ecosystem respiration (SCER) than the treatments where only chemical nitrogen was applied. Rice paddies had significantly (P < 0.05) lower SCER and seasonal cumulative soil respiration (SCSR) than upland plots during the 2003 summer growing season. No-till treatment significantly (P < 0.05) increased the SCER compared with plowing treatment. Plowing practices had different effects on the SCSR in the different growing seasons. The highest annual ecosystem respiration during the 2002‒2003 and 2003‒2004 rotation years was higher than that in previous studies that used the eddy covariance (EC) technique in croplands. The percentage of soil to ecosystem respiration varied from 31% to 81% across treatments. The SCER across treatments during the winter wheat growing seasons was significantly (P < 0.05) correlated with temperature, maximum aboveground biomass (MAB), maximum leaf biomass (MLB), maximum specific leaf area (MSLA) and BTS. Seasonal variations in ecosystem and soil respiration could be modelled by temperature, moisture, AB, LAI and PH. Moreover, the aboveground respiration coefficient decreased with increasing LAI and PH in the winter wheat, maize and rice plots.

Nitrogen leaching from tile‐drained fields and lysimeters receiving contrasting rates and sources of nitrogen

AbstractLeaching of nitrogen from arable land can lead to pollution of groundwater and surface water. Various measures have been implemented in agriculture to reduce leaching, but there is still potential to do more. To find the best agricultural management regime to limit the problem, leaching from soils under different management must be measured. Different methods to estimate leaching are available, but they have not been thoroughly evaluated. This study compared (a) leaching of nitrogen from five different fertilizer treatments differing in amount and source (mineral and organic) of nitrogen and (b) two different methods for measuring leaching (tile‐drained field plots and lysimeters). Nitrogen leaching from five different fertilizer treatments was studied for three years in a tile‐drained field facility and for three of the treatments also for 16 months in a lysimeter facility. Leaching from organic and mineral nitrogen sources was similar in the three‐year field study. Mineral nitrogen input above the economic optimum tended to give greater leaching (by 24%–43%) than nitrogen input at the expected optimum. Measurements in lysimeters and tile‐drained field plots gave similar results, although leaching values tended to be slightly higher (by 18%–25%) in the tile‐drained field. Overall, both facilities give reliable estimates of nitrogen leaching and are suitable for leaching studies.

Using soil hydromorphy degree for adjusting steady-state water table simulations along catenas in semiarid Russia

Mapping soil properties has obvious utility for formulating agricultural management regimes. One that is particularly pertinent in areas with shallow water tables in semiarid regions, especially where catchments have both dry and moist parts, is hydromorphy degree. However, there is no convenient method for converting it to hydrological model state variables, which is a crucial first step for mapping (in the absence of extremely thorough and costly monitoring). Here we propose that the steady state continuity equation in kinematic wave form can be parameterized using expert knowledge of the typical water table depth (WTD) for soils with different hydromorphy degrees. To test the approach, six hillslope-based computational units (catenas) were obtained, for use in simulations, by automated of the Samovetc and Izberdey catchments in the Tambov region (Russia) using lumpR software. Five of the six catenas began at poorly drained flat upslope positions with soils with various degrees of saturation by shallow groundwater and one began at a well-drained upslope position. Each of the six hillslopes had a unique catenary sequence of soils, but each represented a typical unit. We genetically classified soils in the sequences according to hydromorphy degree based on redoximorphic features as diagnostic properties. For each resulting group, a historical database summarizing possible positions of the WTD was used. Application of expert knowledge in this manner alone yielded a broad range of possible WTD values (e.g. 1.5–5 m for a semi-hydromorphic soil) for each soil entity, but linking a catena by the fundamental physical constraint of flow continuity enabled narrowing of the range to 0.2–1 m thereby reducing it by ca. 80%. The results show that the approach could substantially improve crop and water management precision.

Ant community potential for pest control in olive groves: Management and landscape effects

Ants are important pest control agents in many agroecosystems worldwide. However, little is known about how management, landscape complexity, their interaction, and the ecological contrast generated by different agricultural practices affect their communities and the potential pest control they can provide.Here, we surveyed ant communities in 40 paired olive groves with different agricultural management regimes across 20 localities spanning a wide range of landscape complexity at the regional scale. We also conducted field experiments with dummy plasticine models and fresh prey to explore the ant potential to control the two main pests of the olive tree (olive moth and olive fly). In addition, we calculated an index, the Ant-community Predation Function (APF), which informs about the predation pressure exerted by ant communities over these pests.Results show that: a) the maintenance of herb cover at intermediate landscape complexity sites maximizes the abundance and potential for pest control by ants; b) the ecological contrast affects ant abundance and ant richness but does not impact the predation function; c) APF is a good measure of pest control potential at the community level; and, d) Tapinoma nigerrimum is an important ant species for pest control in our system, which seems little affected by local or landscape heterogeneity.The maintenance of herb cover, organic farming and a certain landscape complexity is beneficial for ant communities and increase their contribution to pest control in olive groves.

EDNA‐based biomonitoring at an experimental German vineyard to characterize how management regimes shape ecosystem diversity

AbstractThere is growing interest in the application of sustainable agricultural methods to minimize the environmental impact of farming and thus aiding quantification of the actual benefit that such approaches may confer. We applied DNA metabarcoding with the aim of exploring how the diversity of fungi and arthropods were affected by different agricultural management systems (integrated, organic, biodynamic) at the experimental vineyard of Geisenheim (Rheingau, Germany). Data were generated for the bloom and harvest periods in 2017, using environmental DNA (eDNA) metabarcoding analysis of both soil and vane trap samples. Our data revealed four principal results. (a) Overall richness of vane trap samples was unaffected by the management systems, likely due to the relatively small scale of the plots compared to the ranges of taxa such as the arthropods caught. In contrast, however, the richness of soil‐living taxa appeared to be negatively affected by conventional treatments, especially at harvest. (b) Analysis of similarity revealed that the species composition was significantly differentiated by management systems for both fungal and other taxa in both sample types. (c) Taxonomic analysis of fungi revealed that the management system drove differentiation in the abundance patterns for wine‐related fungi. Overall, our study reiterates the potential of eDNA techniques as a tool for assessing how biodiversity is affected by different agricultural management regimes, and we hope such approaches will be adopted in future research aimed at guiding vineyard management decisions.

The Effect of Increasing Topsoil Disturbance on Surface-Active Invertebrate Composition and Abundance under Grazing and Cropping Regimes on Vertisols in North-West New South Wales, Australia.

Agricultural intensification practices involve varying degrees of disturbance to the soil ecosystem. This study evaluated six agricultural management regimes with increasing levels of topsoil disturbance, on the composition and abundance of surface-active invertebrates on Vertisols at a sub-catchment scale. Two grazing (native and introduced pastures), and four cropping (combining short and long fallow, with zero and conventional tillage) management regimes were examined. Surface-active invertebrates were collected seasonally with pitfall traps over 2 years (8 seasons), and identified to order, while ants (Formicidae) that comprised 47% of total invertebrates collected, were identified to genera. Season had a significant effect on ant abundance and number of genera recorded with higher abundance and twice the number of genera in summer than all other seasons. Ants, particularly Iridomyrmex, were mainly active in summer, while other invertebrates especially Coleoptera, were more active in winter. Surface-active invertebrates were 30% more abundant in grazing than cropping land use types. Native pasture, with little surface soil disturbance, recorded the highest number of invertebrates, mainly ants, compared to other agricultural management regimes. Coleoptera and Dermaptera were higher in abundance under conventional tillage compared with those agricultural management regimes that disturb the topsoil less. Optimizing surface-active invertebrate activity on Vertisols for most taxa will require reducing topsoil disturbance. However, the research findings also suggest that the impact of agricultural management regimes on invertebrate activity was difficult to predict with any certainty as the three main ant genera, and most abundant invertebrate collected, did not respond in a consistent manner.

Economic and food security effects of small-scale irrigation technologies in northern Ghana

Abstract Small-scale irrigation (SSI) technologies can be useful not only to increase crop productivity and income but also as a viable adaptation practice to climate variability. A farm simulation model (FARMSIM) and data from selected SSI technologies piloted in northern Ghana under the ‘Feed the Future-Innovation Lab for Small Scale Irrigation’ (ILSSI) project were used to assess the economic feasibility of the SSI technologies and their potential to improve income and nutrition of smallholder farm households. Three dry season irrigated crops (onion, corchorus, amaranthus) grown under three agricultural water management regimes were analysed. Results show that adoption of the SSI technologies could increase the net farm profit by 154%–608% against the baseline depending on the ‘crop type - SSI technology’ combination. Nutrition levels also improved significantly as a result of the improvements in crop yields due to irrigation and use of complementary inputs. However, the results further reveal that the options that utilize capital-intensive SSI technologies such as solar-powered water pumps to grow high value cash crops are constrained by the high investment cost. Currently, farmers tend to choose low-cost SSI technologies such as a traditional watering-cans, which generate low economic returns. Improving access to credit or alternative financing schemes could mitigate the capital constraints and enable smallholders to gain more benefits from participating in market-oriented high-value irrigated production.

Plant species richness decreased in semi-natural grasslands in the Biosphere Reserve Wienerwald, Austria, over the past two decades, despite agri-environmental measures

Abstract Both, agricultural intensification and abandonment caused a strong decline in plant species richness in semi-natural grasslands in Central Europe within the last decades. At a global scale, the Convention on Biological Diversity targeted at halting the decline of biodiversity by the end of 2010. Agri-environmental schemes (AES) have been developed at the national level to reach this biodiversity target in agricultural areas. We evaluated the effectiveness of Austrian agro-environmental schemes on species-rich grasslands within the UNESCO Biosphere Reserve Wienerwald. We found a general decrease of vascular plant species richness at 95 sites, from an average of 43 species in 1990/92 to 31 species in 2011. The average decrease of species classified as threatened according to the national Red List from 12 to 7 and the parallel increase of widespread, nitrophilous species indicates a reduced conservation value of observed meadows. Species losses did not differ between mesic meadows of the Arrhenatherion type (EU habitat type 6510) and more nutrient-poor, semi-dry Brometalia grasslands (EU habitat type 6210), indicating the sensitivity to changes in agricultural management regimes even for more intensively used grassland types. AES decelerated this overall trend but could not stop biodiversity losses over the past two decades. Although the maintenance of grassland management through AES prevented biodiversity loss in areas which otherwise would have been abandoned, adaptations of the Austrian AES are desirable to effectively conserve biodiversity at agricultural sites.

Taming the torrents: The hydrological impacts of ancient terracing practices in Jordan

Extensive terracing was an important component of the water and agricultural management regime of Nabatean Petra. The exact function(s) of these terraces, qualitatively and quantitatively, is herein investigated. Field studies and computer modeling for two sites within the drainage basin of Petra show that these terraces were highly effective at reducing surface runoff. Different design features seem to have been adapted in order to achieve different objectives at varying sites. For example, the Beidha site in the lower reaches of the catchment area falls within the higher relief Ordovician Disi Sandstone formation area. Here, the terrace system was designed to slow water flow and trap sediments. The terracing greatly reduced surface water flow through the entrapment of sandy loam sediments behind it. On the other hand, the Baqa’a site falls in the upper reaches of the drainage basin within the Upper Cretaceous Amman Silicified Limestone formation. The effect of the terrace system here on runoff is significant, but less than that seen at Beidha. This system was more suited for soil conservation and agriculture, as the soil here in its natural state already had a high infiltration rate. Neglect and abandonment of these terraces at both sites have led to increased runoff, as evidenced by the development of gullies and by periodic flooding downstream in the core of the ancient city. Based on the six modeled cases, terraces can minimize the surface flow by an average of 28%, with values as high as 90% when 2010 precipitation data were used. Conducting an intensive survey within the catchment area surrounding the ancient city of Petra, mapping the ancient terraces, and reviving their function may produce significant results in flood mitigation and control there.

Nitrous Oxide and Methane Fluxes During the Maize Season Under Optimized Management in Intensive Farming Systems of the North China Plain

Addressing concerns about mitigating greenhouse gas (GHG) emissions while maintaining high grain yield requires improved management practices that achieve sustainable intensification of cereal production systems. In the North China Plain, a field experiment was conducted to measure nitrous oxide (N2O) and methane (CH4) fluxes during the maize (Zea mays L.) season under various agricultural management regimes including conventional treatment (CONT) with high N fertilizer application at a rate of 300 kg N ha−1 and overuse of groundwater by flood irrigation, optimal fertilization 1 treatment (OPT1T), optimal fertilization 2 treatment (OPT2T), and controlled-release urea treatment (CRUT) with reduced N fertilizer application and irrigation, and a control (CK) with no N fertilizer. In contrast to CONT, balanced N fertilization treatments (OPT1T, OPT2T, and CRUT) and CK demonstrated a significant drop in cumulative N2O emission (1.70 v.s. 0.43–1.07 kg N ha−1), indicating that balanced N fertilization substantially reduced N2O emission. The values of the N2O emission factor were 0.42%, 0.29%, 0.32%, and 0.27% for CONT, OPT1T, OPT2T, and CRUT, respectively. Global warming potentials, which were predominantly determined by N2O emission, were estimated to be 188 kg CO2-eq ha−1 for CK and 419–765 kg CO2-eq ha−1 for the N fertilization treatments. Global warming potential intensity calculated by considering maize yield was significantly lower for OPT1T, OPT2T, CRUT, and CK than for CONT. Therefore, OPT1T, OPT2T, and CRUT were recommended as promising management practices for sustaining maize yield and reducing GHG emissions in the North China Plain.

Impacts of 9 years of a new conservational agricultural management on soil organic carbon fractions

Labile soil organic carbon pools are widely regarded as valuable indicators of changes in soil C sequestration pools and dynamics induced by different soil management practices. The objective of this study was to evaluate how a new conservational agricultural management (NCAM), which has been proved to be an effective pattern to increase corn yield, affects soil organic C (SOC) and labile SOC pools after a 9-year experiment in Northeast China. Narrow-wide row (1.70m wide row and 0.30m narrow row, corn is sowed in the narrow row with two lines), no-till, residue retention, change of ridge direction, and fallow are adopted for NCAM. Soil under conventional agricultural management (CAM) was also studied to be as a comparison. Soil samples were taken from 0–20 to 20–40cm depths. The results showed that no significant difference was found for SOC between the two managements for both depths, indicating that SOC is a too gross measurement. Soil labile organic C fractions: microbial biomass C, hot-water extractable organic C and permanganate oxidizable C (KMnO4–C) contents were significantly higher under NCAM compared to CAM for both depths, reflecting the build-up of labile C pools under NCAM. In addition, of the three C fractions, KMnO4–C was the most sensitive indicator of changes in SOC induced by different agricultural management regimes. Our results implied that the application of NCAM is important to soil C sequestration and improving soil quality.

How can straw incorporation management impact on soil carbon storage? A meta-analysis

Straw incorporation (SI) is a common practice in China and has important implications for agricultural sustainability. This study aimed to quantitatively summarise the response of top soil (0–20 cm) carbon (C) to SI under different agricultural management regimes. Results indicated that compared with straw removal (SR), SI significantly increased soil C storage by 12 %. Moreover, incorporation of chopped straw with tillage treatment (ploughing and rotary tillage) increased C storage compared to unchopped straw without tillage treatment. SI implementation with upland cropping, in the northwest and northeast resulted in higher C storage compared with rice cropping, and in the northern and southern regions. Changes in soil C were observed based on SI variables, including tillage and straw amounts in fine-textured soils, however straw amount rather than tillage treatment exhibited a greater influence on soil C in coarse-textured soils. We concluded SI implementation with increased amounts of chopped straw for a longer duration was favourable to soil C sequestration in Chinese croplands. Furthermore, we estimated if SI was popularised across all of China’s agricultural regions, soil C sequestration potential would reach 48.2 ~ 56.2 Tg C year−1. SI practices should therefore be encouraged.

Chinese Land‐Based Interventions in Senegal

ABSTRACTAs Chinese land‐based interventions multiply across the African continent, this article focuses on a single Chinese–Senegalese government‐run agriculture demonstration centre to provide insight into the daily realities of Chinese–African interactions on African land. Ethnographic methodologies are employed to examine practices and discourses on agricultural governance among Chinese and Senegalese informants. Building on theories of agriculture as performance, I show how distinct repertoires for land management are negotiated and reshaped by different subjects in a kind of improvised dance, where individuals’ improvisations lead to unanticipated project outcomes. What emerges is a picture of a Chinese agricultural management regime for African land that is simultaneously fraught with conflict, while also replete with collaboration benefiting some smallholder farmers. This actor‐oriented approach provides a critical empirical lens as well as a research framework for engaging more constructively with Chinese in large‐scale land acquisitions. I argue that ‘land grabbing’ must be seen not as a straightforward, linear process of state or corporate takeover of global land, but as a dynamic performance of negotiation among diverse state actors, corporate players and citizens — one that will reshape global development in unanticipated ways.

Balancing the Tradeoffs between Ecological and Economic Risks for the Great Barrier Reef: A Pragmatic Conceptual Framework

ABSTRACT Coral reefs are threatened globally by the climatic consequences of rising atmospheric CO2 levels; in many regions they are also threatened locally, for example, by reductions in the water quality of runoff from adjacent catchments. Interaction between global and local pressures makes it possible to use local actions to mitigate the impacts of climate change. To this end, managers and policy-makers are seeking to implement agricultural land management regimes that improve runoff water quality and thereby reduce risks to the Great Barrier Reef. Although components of the Great Barrier Reef Region have been researched for some time, a systemic approach capable of representing the Region's key functional relationships as a social–ecological system is lacking. Here we provide a conceptual framework of the Great Barrier Reef social–ecological system that identifies a range of complex socioeconomic tradeoffs that may be required to maintain resilient reefs under climate change. The conceptual framework is the first step toward development of a functional analytical tool that is capable of helping policy-makers choose between alternative management actions.

Tracing sources of soil nitrate using the dual isotopic composition of nitrate in 2 M KCl-extracts

Soils comprise a critical interface between the atmosphere, lithosphere, hydrosphere and biosphere, and play a major role in the cycling of nitrogen (N), an element crucial to plant growth. Isotope techniques constitute a powerful tool to study the origin and fate of N compounds (e.g. NO 3 −) within the environment including soils. The objective of our study was to test the usefulness of the isotope composition of soil NO 3 − extracted with 2 M KCl (soil NO 3) as a tool to investigate the origin and fate of NO 3 − in the environment. Specifically issues related to repeat extractions, crop type, length of fertilization, and soil depth were addressed. Soils from four contrasting agricultural management regimes were sampled. Within the relatively confined study area (4 ha), the isotopic compositions of soil NO 3 differed markedly due to management treatments (up to 6 and 17‰ for δ 15N and δ 18O, respectively), but were repeatable among replicate plots (±1‰). Differences in both δ 15N and δ 18O values were observed between legume and non-legume treatments, as well as fertilized versus non-fertilized treatments, which were larger than the variability observed between replicate plots. Differences in the isotopic composition of extractable soil nitrate were not limited to the surface layer, but also occurred within deeper soil layers. This study indicates that the analysis of the natural abundance stable isotope composition of soil NO 3 may provide a promising additional tool for tracing the origin and fate of NO 3 − in the soil zone.

Survey of the bryophytes of arable land in Britain and Ireland 1: a classification of arable field assemblages

Knowledge of the distribution of arable bryophytes lags behind that of bryophytes of many other habitats, and we have almost no information on their occurrence in relation to crop type and agricultural management regime. A survey of arable fields in Britain and Ireland carried out by members of the British Bryological Society in 2001–05 was designed to provide such baseline data. We surveyed a stratified random sample of 200 fields in the main areas of arable agriculture and a further 620 fields in these areas and in areas where arable fields are less frequent. The species present in each field were listed and their frequency within the field assessed. Data on the crop, the cover of vascular plants, bryophytes, trash and bare soil, and the pH and texture of the soil were recorded for each field. Six species assemblages are described on the basis of a classification of the species recorded in each field and their frequency values. The Tortula truncata–Anthoceros and Dicranella staphylina–Riccia glauca assemblages are the most species-rich and are concentrated on acidic soils in northern and western Britain and in Ireland. By contrast, the Barbula unguiculata–Bryum klinggraeffii and Phascum cuspidatum–Microbryum davallianum assemblages are mainly found on calcareous soils in southern and eastern England. The Bryum dichotomum–Marchantia polymorpha assemblage is characterised by widespread, weedy generalist species and is concentrated in East Anglia. The final assemblage, Brachythecium rutabulum–Fissidens taxifolius, characteristically occurs in late-successional fields and was scattered throughout the area sampled. A comparison of the results from Kent with those of a survey of Kentish fields (using a different methodology) by A.G. Side in 1973–74 suggests that the Bryum dichotomum–Marchantia polymorpha assemblage may possibly have replaced the Dicranella staphylina–Riccia glauca assemblage on acidic soils in the last 30 years. The considerable geographical variation within the arable flora of Britain and Ireland revealed by the survey should be taken into account when assessing the meagre evidence for historic changes in the arable bryophyte flora.

Soil Microbial Activity in Conventional and Organic Agricultural Systems

The aim of this study was to evaluate microbial activity in soils under conventional and organic agricultural system management regimes. Soil samples were collected from plots under conventional management (CNV), organic management (ORG) and native vegetation (AVN). Soil microbial activity and biomass was significantly greater in ORG compared with CNV. Soil bulk density decreased three years after adoption of organic system. Soil organic carbon (SOC) was higher in the ORG than in the CNV. The soil under organic agricultural system presents higher microbial activity and biomass and lower bulk density than the conventional agricultural system.