Rothamsted Experimental Station Research Articles

Prediction of future microplastic accumulation in agricultural soils

This study shows the general exponential rise in microplastic accumulation in agricultural soils, with fertilizer application speeding up this increase, and future predictions of microplastic concentrations. Utilizing data from the Broadbalk winter wheat experiment at Rothamsted Research, UK, from 1846 to 2022, Poisson regression models were applied to microplastic counts under different soil treatments, including farmyard manure, inorganic fertilizers, and control conditions. A mass conversion factor was applied to obtain the w/w relationship. Results indicated a significant annual increase in microplastic concentrations across all treatments, with fertilized soils showing a notably higher accumulation rate. Our study forecasts that, in 50 and 100 years from now, soils treated with fertilizers are expected to reach microplastic concentrations of 168.9 mg kg−1 (95% CI: 60.32–473.09) and 1159 mg kg−1 (95% CI: 200.49–6699.8) respectively, levels converging on those used in many experiments. This highlights the urgent need for strategies to mitigate microplastic pollution in agricultural fields. The results also help to choose predicted concentrations in global change experiments, as well as to motivate further research to explore the mechanisms of microplastic accumulation and the integration of these insights into broader agricultural and ecological models to guide sustainable practices and environmental conservation.

Soil nitrogen and phosphorus regulate decomposition of organic nitrogen compounds in the rothamsted experiment

The effects of long-term N and P fertilisation on soil organic nitrogen (SON) turnover are unclear. We sampled soils fertilised by N and/or P since 1843 at Rothamsted Research to investigate the effects of long-term N and P fertilisation on high- or low-molecular-weight SON decomposition and gross N mineralisation. Short-term assays with added 14C-labelled proteins, peptides, and amino acids and gross organic N mineralisation were measured, and the microbial communities and functions were also assessed in parallel. Long-term N fertilisation increased the contents of soil extractable organic N and peptides but decreased organic N-hydrolysing enzyme activities (N-acetyl-β-D-glucosaminidase and leucine aminopeptidase). Fertilisation with P and N accelerated and reduced the decomposition of 14C-labelled organic N compounds, respectively. The decomposition of peptides and amino acids, as labile SON components, was mainly regulated by soil P content because microbial biomass and activity were more sensitive to P fertilisation than to N fertilisation. Gross NH4+/NO3− production and consumption were accelerated by 41%–60% under N fertilisation but remained unchanged under P fertilisation compared to the unfertilised treatment. Metagenomic sequencing showed that N fertilisation increased microbial diversity and enriched functional genes associated with organic N decomposition, compared to the unfertilised treatment. P fertilisation had no effect on the abundance of these functional genes. In agricultural practices, it is essential to comprehensively consider the interaction between N and P fertilisation to optimise the cycling and utilisation of SON.

CARBON ISOTOPE CHANGES THROUGH THE RECENT PAST: F14C AND δ13C VALUES IN SINGLE BARLEY GRAIN FROM 1852 TO 2020

ABSTRACT Radiocarbon (F14C) and stable carbon (δ13C) values were measured in single grains of spring barley (Hordeum vulgare L.) from the sample archive from two adjacent sites of the Long-term Experiments (LTEs) Hoosfield Spring Barley at Rothamsted Research (Harpenden, Hertfordshire, UK), covering the growing periods (March to September) of 1852 to 2020. F14C data of the barley grain confirm that recent values are approaching and will decline below the “nominal” F14C value of 1, tracking a similar decrease reported in other studies. Importantly, the measured δ13C values reveal a different temporal decline over the pre-bomb and post-bomb timescale. Detailed statistical analysis of δ13C data along with δ13C analysis of independent, archived barley mash samples, verifies and quantifies the extent and rate of this decline. Evidence presented from the barley grain and barley mash samples suggests a clear breakpoint in δ13C data occurring in 1995, where the rate of change alters, in that the slope in δ13C data for the pre-1995 period is declining at 1.4‰ per century, and the slope in δ13C for the post-1995 period is declining at 3.6‰ per century. Such a consistent shift in δ13C data could be used with F14C values to extend the use of the bomb peak for forensic, ecological, and environmental applications.

Results of Long Term Fertiliser Experiments - Use in Sustainable Soil Fertility Protection Measures

Long-term experimental research is a model for a superior approach to the long-term effects of vegetation and plant production factors, in relation to the modification of soil-plant components, their productivity, environmental protection and food security. In their fairly well-established and evaluated existence of 180 years, one can assess and record the existence of these experiments on almost all continents, with particular and relevant responses to be implemented for the development of sustainable systems in the development of agriculture and the resolution in time of contemporary challenges for both agriculture and the environment. (Recording of the 180th anniversary of the founding of the "long term model" at Rothamsted - "Three - day hybrid event hosted online and at Rothamsted Research, West Common Harpenden" UK, 20th-22nd June 2023). This paper aims to interpret the changes in the soil-plant system, based on studies and research in experimental and soil analysis field, after long term effects in the experiments at Băcăinți - OSPA Alba and Turda - SCDA, with subsequent proposals for protection and increase of soil fertility and environmental conditions. In the same context, certain interpretations and limits are promoted in the foundation of agrochemical measures for fertility modelling and increased effect of fertilizers.

Design of Agricultural Field Experiments Accounting for both Complex Blocking Structures and Network Effects

We propose a novel model-based approach for constructing optimal designs with complex blocking structures and network effects for application in agricultural field experiments. The potential interference among treatments applied to different plots is described via a network structure, defined via the adjacency matrix. We consider a field trial run at Rothamsted Research and provide a comparison of optimal designs under various different models, specifically new network designs and the commonly used designs in such situations. It is shown that when there is interference between treatments on neighboring plots, designs incorporating network effects to model this interference are at least as efficient as, and often more efficient than, randomized row–column designs. In general, the advantage of network designs is that we can construct the neighbor structure even for an irregular layout by means of a graph to address the particular characteristics of the experiment. As we demonstrate through the motivating example, failing to account for the network structure when designing the experiment can lead to imprecise estimates of the treatment parameters and invalid conclusions.Supplementary materials accompanying this paper appear online.

Performance and enteric methane emissions from housed beef cattle fed silage produced on pastures with different forage profiles.

Methane (CH4) produced by ruminants is a significant source of greenhouse gases from agriculture in the United Kingdom (UK), accounting for approximately 50% of the emissions in this sector. Ration modification is linked to changes in rumen fermentation and can be an effective means of CH4 abatement. In temperate climate countries, forage silage represents a major feed component for cattle during the housing period. The objective of this study was, therefore, to compare enteric CH4 emission from cattle offered silage produced from different types of grassland. Beef cattle, steers (n=89) and heifers (n=88) with average liveweight (LW) of 328±57.1kg were evaluated during two housing seasons (2016-2017 and 2017-2018) from November to April, at the Rothamsted Research North Wyke Farm Platform (UK). The treatments corresponded to three diet types, comprising silage harvested from three different pastures: MRG, monoculture of perennial ryegrass (PRG, Lolium perenne L.cv. AberMagic), bred to express the high-sugar phenotype; RG-WC, a mixed sward comprised of the same perennial ryegrass cultivar with white clover (Trifolium repens L.) with a target clover proportion of 30% as land cover; and permanent pasture (PP) dominated by PRG and a small number of non-introduced species. MRG and PP received 160-200kgN/ha/year. Cattle were weighed every 30days, and the enteric CH4 emission was determined using GreenFeed automated systems. No significant differences in enteric CH4 emission per head or per kg LW were observed between treatments. However, emission expressed per average daily gain (ADG) in LW was greater (P<0.001) for MRG compared with RG-WC and PP, at 270, 248 and 235g CH4/kg ADG, respectively. This related to a lower ADG (P=0.041) for the animals fed MRG silage compared with RG-WC and PP which were similar, with respective values of 0.67, 0.71 and 0.74kg/day. The forages compared in this study showed little or no potential to reduce enteric CH4 emission when fed as silage to growing beef cattle during the winter housing period.

Effect of Different Organic Amendments on Actual and Achievable Yields in a Cereal-Based Cropping System

Soil fertility is at risk in intensive cropping systems when using an exclusive regime of inorganic fertilisers without returning sufficient organic matter to the soil. Our objective was to evaluate the long-term effects of commonly used organic amendments interacting with different rates of inorganic nitrogen fertiliser on crop yields of winter wheat. Yield data from winter wheat were collected for five seasons between 2013 and 2019 from a continuous field trial based at Rothamsted Research, SE England. Organic amendments (anaerobic digestate, compost, farmyard manure, and straw at a rate of 0 and 2.5 ton C per hectare) and five rates of inorganic nitrogen fertiliser (NH4NO3 at 0, 80, 150, 190, 220 kg N ha−1) were applied to winter wheat grown in an arable rotation. At the same inorganic N rate, grain yields for the different organic amendment treatments (excluding the straw treatment) were statistically similar but significantly greater than the unamended control treatment. The nitrogen rate required for optimum yields tended to be lower in plots receiving a combination of organic amendments and mineral fertiliser. Based on the observed and modelled response functions, organic amendments excluding straw increased maximum achievable yields compared to non-amended controls. The size of the effect varied between seasons and amendments (+4.6 to +19.0% of the control yield), increasing the mean maximum achievable yield by 8.8% across four seasons. We conclude that the application of organic amendments can increase the yield potential in winter wheat substantially over what is achievable with inorganic fertiliser only.

News and perspectives for Annals of Applied Biology in 2023: Looking forward to more and more submissions

News and perspectives for <scp><i>Annals of Applied Biology</i></scp> in 2023: Looking forward to more and more submissions

Contributor biographies

Contributor biographies

BCPC Diseases Review 2022 – Changing Challenges and Changing Tools for Integrated Crop Management

John Lucas, Editorial Board Member and Jon West, Rothamsted Research suggested that the threat posed by Fusarium is likely to increase due to a number of factors including maize crops extending further northwards. The second presentation, given by Derek Croucher, focused on the impact of mycotoxins on producers. The main processor focus on mycotoxins both in the field and during storage is compliance with current legislation, including the ability to test effectively and analyse samples, as well as mitigation measures. There are parallels with legislation of plant protection products, and concerns about potential changes due to exit from the EU. To date these have not occurred, but there is the possibility of GB adoption of EU rules by retailers to facilitate trade. The Food Standards Agency have a priority list of contaminants with maximum limits for mycotoxins in particular foodstuffs, exemplified by current permitted levels for T-2/HT-2 toxins in unprocessed and milled oats. The primary problem in UK oats is Fusarium langsethiae, which causes a mainly symptomless disease, varying in incidence from year to year, with some "high" years, especially in Scotland. There are no commercially viable field mitigation measures. Milling reduces contamination, but this varies and is not batch to batch predictable. There is no reliable rapid test for toxin contamination in oats, and testing by LC-MS/MS is expensive and takes time. In severe years, around 10 – 30% of unprocessed oats would be non-compliant, and as much as 20% of processed products. Identification of compliant versus non-compliant products is challenging and poses a significant risk of recall and reputational damage. The 2022 Diseases review was held at the NIAB Park Farm, Cambridge on October 19th 2022 with a mix of in person and online delegates. The meeting was chaired by Jenna Watts, Head of Plant Health and IPM at the Agriculture and Horticulture Development Board (AHDB). She outlined the current issues and challenges for crop production including climate change, the evolution of pathogen populations to overcome host resistance and pesticides, alterations in the regulatory framework, and changing consumer priorities. New tools are available for disease diagnosis and control, but how can they be most effectively used for integrated crop management? The first two presentations dealt with the issue of mycotoxin contamination of small grain cereals. Professor Simon Edwards (Harper Adams University College) described the various mycotoxins in cereal crops infected by different Fusarium species causing the head blight complex. On wheat the main problems are deoxynivalenol (DON) and zearalenone (ZON) produced by F. graminearum and F. culmorum, while HT-2 and T-2 toxins produced by F. langsethiae and F. sporothrichioides are more of an issue in oats. Mycotoxin profiles vary by cereal, region and season, and exceed permitted regulatory limits in some crops and years. Risk factors for head blight are well known and include crop debris (the main source of inoculum), a warm spring, and heavy rainfall with high humidity in summer. In experimental trials, agronomy accounts for relatively little of the variation in mycotoxin levels. Maize as the previous crop is a major risk factor, along with min tillage and direct drilling. Ploughing or chopping and mixing of debris reduce mycotoxin levels in the crop. There is limited current varietal variation in resistance to head blight. Some fungicides including prothioconazole, metconazole and tebuconazole applied at T3 can reduce DON levels, while Adepidyn (pydiflumetofen) a new but not yet registered SDHI shows some promise for head blight control and toxin reduction. Integrated management to minimize Fusarium mycotoxins in milling wheat therefore combines the use of less susceptible varieties, avoiding high risk crops such as maize in rotations, intense cultivation if a high-risk previous crop has been grown, application of an effective fungicide (or mixture) at T2 and especially T3, and ensuring a timely harvest as late harvesting is associated with higher mycotoxin levels. It was noted that these recommendations are not easy to reconcile with some crop management trends such as reducing cultivations. Professor Edwards also presented some data on HT-2 and T-2 occurrence in oats, and tactics for reducing risk such as switching to spring varieties, or taller more Fusarium resistant varieties, long rotations, and the use of cultivations. Climate change models suggest that the threat posed by Fusarium is likely to increase due to a number of factors including maize crops extending further northwards,

Interview with Prof. Nigel G. Halford, Rothamsted Research, United Kingdom

Interview with Prof. Nigel G. Halford, Rothamsted Research, United Kingdom

CO2 fluxes from three different temperate grazed pastures using Eddy covariance measurements

Grasslands cover around 25% of the global ice-free land surface, they are used predominantly for forage and livestock production and are considered to contribute significantly to soil carbon (C) sequestration. Recent investigations into using ‘nature-based solutions’ to limit warming to <2 °C suggest up to 25% of GHG mitigation might be achieved through changes to grassland management. In this study we evaluate pasture management interventions at the Rothamsted Research North Wyke Farm Platform, under commercial farming conditions, over two years and consider their impacts on net CO2 exchange. We investigate if our permanent pasture system (PP) is, in the short-term, a net sink for CO2 and whether reseeding this with deep-rooting, high-sugar grass (HS) or a mix of high-sugar grass and clover (HSC) might increase the net removal of atmospheric CO2. In general CO2 fluxes were less variable in 2018 than in 2017 while overall we found that net CO2 fluxes for the PP treatment changed from a sink in 2017 (−5.40 t CO2 ha−1 y−1) to a source in 2018 (6.17 t CO2 ha−1 y−1), resulting in an overall small source of 0.76 t CO2 ha−1 over the two years for this treatment. HS showed a similar trend, changing from a net sink in 2017 (−4.82 t CO2 ha−1 y−1) to a net source in 2018 (3.91 t CO2 ha−1 y−1) whilst the HSC field was a net source in both years (3.92 and 4.10 t CO2 ha−1 y−1, respectively). These results suggested that pasture type has an influence in the atmospheric CO2 balance and our regression modelling supported this conclusion, with pasture type and time of the year (and their interaction) being significant factors in predicting fluxes.

Is it possible to attain the same soil organic matter content in arable agricultural soils as under natural vegetation?

Clearing natural vegetation to establish arable agriculture (cropland) almost invariably causes a loss of soil organic carbon (SOC). Is it possible to restore soil that continues in arable agriculture to the pre-clearance SOC level through modified management practices? To address this question we reviewed evidence from long-term experiments at Rothamsted Research, UK, Bad Lauchstädt, Germany, Sanborn Field, USA and Brazil and both experiments and surveys of farmers’ fields in Ethiopia, Australia, Zimbabwe, UK and Chile. In most cases SOC content in soil under arable cropping was in the range 38–67% of pre-clearance values. Returning crop residues, adding manures or including periods of pasture within arable rotations increased this, often to 60–70% of initial values. Under tropical climatic conditions SOC loss after clearance was particularly rapid, e.g. a loss of &gt;50% in less than 10 years in smallholder farmers’ fields in Zimbabwe. If larger yielding crops were grown, using fertilizers, and maize stover returned instead of being grazed by cattle, the loss was reduced. An important exception to the general trend of SOC loss after clearance was clearing Cerrado vegetation on highly weathered acidic soils in Brazil and conversion to cropping with maize and soybean. Other exceptions were unrealistically large annual applications of manure and including long periods of pasture in a highly SOC-retentive volcanic soil. Also, introducing irrigated agriculture in a low rainfall region can increase SOC beyond the natural value due to increased plant biomass production. For reasons of sustainability and soil health it is important to maintain SOC as high as practically possible in arable soils, but we conclude that in the vast majority of situations it is unrealistic to expect to maintain pre-clearance values. To maintain global SOC stocks at we consider it is more important to reduce current rates of land clearance and sustainably produce necessary food on existing agricultural land.

Potential Co‐benefits and trade‐offs between improved soil management, climate change mitigation and agri‐food productivity

AbstractMaximising resource‐use efficiency, productivity and environmental sustainability are all fundamental requirements to raise global food production by ~70 per cent in order to feed a world population of ~9.7 billion people by 2050. Perhaps the most vital resource within our capacity to achieve this goal is our soil. Broadly, the fundamental question concerns whether or not satisfying this production demand will accelerate soil degradation, climate change, and the loss of soil carbon stocks. This paper builds upon the outputs of the UK Charity ‘Food &amp; Farming Futures’ (chaired by Lord Curry of Kirkharle) virtual workshop held on 23 March 2021, entitled ‘Capturing the Potential of Soil’. The event focussed on the link between soil health, primarily soil organic carbon (SOC), and agricultural productivity. Supported with commentaries by Professor Pete Smith (University of Aberdeen and Science Director of the Scottish Climate Change Centre of Expertise) and Professor Steve McGrath (Head of Sustainable Agricultural Sciences at Rothamsted Research), specific focus will be given to the research challenges within the UK’s ability to improve soil health and functionality, the implementation priorities that must be held in order to improve soil management by 2050 and what the potential co‐benefits could be. These co‐benefits were scattered across environmental, economic, social and political issues, yet they may be summarised into six primary co‐benefits: developing natural capital, climate change mitigation, carbon trading, improvements in crop yield, animal performance and human health (nutrition). Additionally, the main barriers to improved soil management practices are centred on knowledge exchange‐regarding agri‐environmental techniques—whilst the most impactful solutions rely on soil monitoring, reporting and verification.

EU Policies Led to Collapse of Major Biofuel Crop in UK and Europe, Says Report

Contradictory EU policies first encouraged and then undermined the farming of a major biofuel in Europe, according to a new analysis. Climate change polices initially rewarded the widespread planting of oilseed rape – the world's most important vegetable oil after soybean – but subsequent pesticide laws have ultimately led to very large yield losses across the continent in recent years. This collapse of oilseed rape farming in the UK and Europe had led to a reliance on imported oils – including palm oil, the growing of which is often responsible for tropical deforestation, and oilseed rape from countries still using pesticides banned by the EU. The findings of the report were presented at a meeting of the British Crop Protection Council by lead author, Dr Patricia Ortega-Ramos from Rothamsted Research. Speaking ahead of the meeting, she said the series of EU policy decisions essentially 'created a serious crop pest. It is a great example of how a better understanding of pests and joined up decision making are going to be vital if we are to reform farming. Contradictory EU policies first encouraged and then undermined the farming of a major biofuel in Europe, according to this new analysis. Climate change polices initially rewarded the widespread planting of oilseed rape – the world's most important vegetable oil after soybean – but subsequent pesticide laws have ultimately led to very large yield losses across the continent in recent years. This collapse of oilseed rape farming in the UK and Europe had led to a reliance on imported oils – including palm oil, the growing of which is often responsible for tropical deforestation, and oilseed rape from countries still using pesticides banned by the EU. The EU'S 2009 Sustainable Use of Pesticides Directive was not well implemented, and as a result of that and subsequent decisions, the cabbage stem flea beetle has now become a serious pest. The area of oilseed rape being grown is now falling sharply, with huge financial consequences for farmers and major environmental consequences for all of us.

Fertilizer P-derived uranium continues to accumulate at Rothamsted long-term experiments

The application of phosphorus (P) fertilizers inevitably contributes to the accumulation of trace elements, such as uranium (U), in agricultural soils. The fertilizer-derived U accumulation was first reported in Rothamsted Research in 1979. In the present study, we expand this early key research by evaluating the fertilizer-derived U accumulation in topsoil (0–23 cm) from 1876 to the 2010s. We found that total U accumulation rates ranged from 2.8 to 6.1 μg U kg−1 yr−1 at the Broadbalk and Park Grass, respectively, being similar to those observed 40 years ago. This highlights that U accumulation is still an ongoing process in Rothamsted. Fortunately, the proportion of fertilizer-derived U did not significantly increase in the ammonium acetate extractable (‘proxy’ of plant-available) fraction over 130 years. In addition, we compiled an overview of the global rate of mineral P fertilizer-derived U accumulation in agricultural systems using existing literature (36 experimental trials, from 11 countries). The resulting dataset predicts an estimated mean U accumulation of 0.85 μg U kg−1 soil for an annual application of 1 kg P ha−1 in the topsoil of agricultural systems (0.26 μg U kg−1 per kg P ha−1 for arable land and 1.34 μg U kg−1 per kg P ha−1 for grassland). The annual U accumulation per applied kg P ha−1 being 0.08 (Broadbalk) and 0.17 μg U (Park Grass) corresponds to around one-third and one-eighth of the worldwide mean U accumulation for their respective agricultural systems, suggesting ‘relatively’ low U contents of the applied P fertilizers. Our study underscores that fertilizer-derived U accumulation is a persistent problem on the global scale, even if at different rates, and therewith suggests an evaluation of current regulatory limits and acceptable U input levels from P fertilization.

THE ROLE OF LONG-TERM EXPERIMENTS IN VALIDATING TRAIT-BASED APPROACHES TO ACHIEVING MULTIFUNCTIONALITY IN GRASSLANDS

<List> <ListItem><ItemContent> ● Data from the Park Grass Experiment shows inherent trade-offs between species richness, biomass production and soil organic carbon. </ItemContent></ListItem> <ListItem><ItemContent> ● Soil organic carbon is positively correlated with biomass production that increases with fertilizer additions. </ItemContent></ListItem> <ListItem><ItemContent> ● Variance in outcomes can be understood in terms of the dominant ecological strategies of the plant communities indicated by functional traits. </ItemContent></ListItem> <ListItem><ItemContent> ● There was an indication that data on traits associated with the spatiotemporal pattern of resource capture could be used to design species mixtures with greater resource use complementarity, increasing species richness without sacrificing productivity. </ItemContent></ListItem> <ListItem><ItemContent> ● Variance in soil organic carbon was positively correlated with pH. </ItemContent></ListItem></List> Quantifying the relationships between plant functional traits and ecosystem services has been promoted as an approach to achieving multifunctional grassland systems that balance productivity with other regulating, supporting and cultural services. Establishing trade-offs and synergies between traits and services has largely relied on meta-analyses of studies from different systems and environments. This study demonstrated the value of focused studies of long-term experiments in grassland systems that measure traits and services in the same space and time to better understand the ecological constraints underlying these trade-offs and synergies. An analysis is presented that uses data from the Park Grass Experiment at Rothamsted Research on above-ground productivity, species richness and soil organic carbon stocks to quantify the relationships between these three outcomes and the power of variance in plant functional traits in explaining them. There was a trade-off between plots with high productivity, nitrogen inputs and soil organic carbon and plots with high species richness that was explained by a functional gradient of traits that are indicative of contrasting strategies of resource acquisition of resource conservation. Examples were identified of using functional traits to identify opportunities for mitigating these trade-offs and moving toward more multifunctional systems.

Evolution of the transport properties of soil aggregates and their relationship with soil organic carbon following land use changes

Aggregates are functional units to describe the impact of soil structural changes on physical and biogeochemical processes in soil. Both incubation and field experiments have shown that changing agricultural practices could reshape the intra-aggregate structure in a matter of days, but most such data were obtained from a single time-point and it is hence impossible to interpret that such a change was just a temporal transition or the new equilibria towards which the aggregates had evolved following the management changes. Understanding this is indispensable as intra-aggregate structure and its ability to transport substrates modulate all biogeochemical processes involved in soil carbon and nutrient cycle. This paper investigates this using soil samples archived from a reversion experiment initiated in 2008 at Rothamsted Research (UK), where parts of a plot that had been fallow since the 1950 s were converted to wheat or grass in 2008. We used X-ray Computed Tomography images, acquired at voxel size 1.5 µm, of aggregates in the archived soils to investigate the evolution of transport property of the aggregates over time, as well as its relationship with soil organic carbon (SOC). We also evaluated the development of pore connectedness following the conversion. The results show that the transport ability of the aggregates explains the SOC change much better than the porosity, and that noticeable changes in porosity of the connected pores and their ability to transport substrates did not emerge until the sixth year after the conversion. Ten years after the conversion, there was still no sign of the porosity of the connected pores and the bulk diffusion coefficient to plateau. In addition, we found the conversion to grass changed the intra-aggregate pore geometry significantly in that the bulk diffusion coefficients of their aggregates trends with their porosities in a way differing significantly from those for the bare fallow and arable treatments. All these suggest that the intra-aggregate reconfiguration following the conversion is a slow process, and that the ability of pore space to transport substrates is more important than the habitat they provide in SOC stabilisation.

Changes in agricultural climate in South-Eastern England from 1892 to 2016 and differences in cereal and permanent grassland yield

The long-term increasing trend of annual mean temperature is only one aspect of recent climate change. Other changes in climate, seen in within-year weather patterns relevant to crop production, have also occurred since the late-19th Century. Multivariate analysis combining Principal Components Analysis and K-means clustering applied to temporal meteorological datasets (monthly summaries of rainfall, temperature and sunlight duration at Rothamsted Research, UK, between 1892 and 2016) identified ten distinct clusters of years, each with different annual weather patterns. The frequency of occurrence of the years within each cluster altered considerably during this period, with the late 20th and early 21st Century distinctly different to earlier in the 20th Century, providing clear evidence of climate change with regard to the whole weather profile rather than just warming alone. The most-frequently represented cluster of the 21st Century to date had warmer temperatures with more intense rainfall but a dry June, compared to all other clusters. Half of the clusters identified were not represented in the most-recent 25-year period. Analysis of the total biomass yield of winter wheat (Triticum aestivum L.), spring barley (Hordeum vulgare L.), and grassland amongst the different weather clusters showed that years in clusters typical of the 20th Century climate provided greater off-take than those from the early-21st Century, but this impact was less for the pasture than for the two cereal crops implying herbage production was the more resilient to the changing climate at this site.

Editorial and News

Editorial and News