Browsing by Author "Whitmore, Andrew P."

Now showing 1 - 12 of 12
  • Thumbnail Image
    ItemOpen Access
    Defining and quantifying the resilience of responses to disturbance: a conceptual and modelling approach from soil science
    (Nature Publishing Group, 2016-06-22) Todman, Lindsay; Fraser, Fiona; Corstanje, Ronald; Deeks, Lynda K.; Harris, Jim A.; Pawlett, Mark; Ritz, Karl; Whitmore, Andrew P.
    There are several conceptual definitions of resilience pertaining to environmental systems and, even if resilience is clearly defined in a particular context, it is challenging to quantify. We identify four characteristics of the response of a system function to disturbance that relate to “resilience”: (1) degree of return of the function to a reference level; (2) time taken to reach a new quasi-stable state; (3) rate (i.e. gradient) at which the function reaches the new state; (4) cumulative magnitude of the function (i.e. area under the curve) before a new state is reached. We develop metrics to quantify these characteristics based on an analogy with a mechanical spring and damper system. Using the example of the response of a soil function (respiration) to disturbance, we demonstrate that these metrics effectively discriminate key features of the dynamic response. Although any one of these characteristics could define resilience, each may lead to different insights and conclusions. The salient properties of a resilient response must thus be identified for different contexts. Because the temporal resolution of data affects the accurate determination of these metrics, we recommend that at least twelve measurements are made over the temporal range for which the response is expected.
  • Thumbnail Image
    ItemOpen Access
    Distinct respiratory responses of soils to complex organic substrate are governed predominantly by soil architecture and its microbial community
    (Elsevier, 2016-12-01) Fraser, Fiona; Todman, Lindsay C.; Corstanje, Ronald; Deeks, Lynda K.; Harris, Jim A.; Pawlett, Mark; Whitmore, Andrew P.; Ritz, Karl
    Factors governing the turnover of organic matter (OM) added to soils, including substrate quality, climate, environment and biology, are well known, but their relative importance has been difficult to ascertain due to the interconnected nature of the soil system. This has made their inclusion in mechanistic models of OM turnover or nutrient cycling difficult despite the potential power of these models to unravel complex interactions. Using high temporal-resolution respirometery (6 min measurement intervals), we monitored the respiratory response of 67 soils sampled from across England and Wales over a 5 day period following the addition of a complex organic substrate (green barley powder). Four respiratory response archetypes were observed, characterised by different rates of respiration as well as different time-dependent patterns. We also found that it was possible to predict, with 95% accuracy, which type of respiratory behaviour a soil would exhibit based on certain physical and chemical soil properties combined with the size and phenotypic structure of the microbial community. Bulk density, microbial biomass carbon, water holding capacity and microbial community phenotype were identified as the four most important factors in predicting the soils’ respiratory responses using a Bayesian belief network. These results show that the size and constitution of the microbial community are as important as physico-chemical properties of a soil in governing the respiratory response to OM addition. Such a combination suggests that the 'architecture' of the soil, i.e. the integration of the spatial organisation of the environment and the interactions between the communities living and functioning within the pore networks, is fundamentally important in regulating such processes.
  • Thumbnail Image
    ItemOpen Access
    Effect of different organic amendments on actual and achievable yields in a cereal-based cropping system
    (Springer, 2023-02-27) Albano, Xavier; Whitmore, Andrew P.; Sakrabani, Ruben; Thomas, Cathy L.; Sizmur, Tom; Ritz, Karl; Harris, Jim A.; Pawlett, Mark; Watts, Chris; Haefele, Stephan M.
    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.
  • Thumbnail Image
    ItemOpen Access
    The effect of organic farming on soil physical properties, infiltration and workability
    (Cranfield University, 2011-02) Hathaway-Jenkins, Laura Jane; Godwin, R. J.; Sakrabani, Ruben; Whitmore, Andrew P.; Pearce, B.
    Organically managed land has increased to 4 % of the total area of agricultural land in the UK. Changing land management can impact upon the rural environment (soils, hydrology and biodiversity) and rural community (socio-economics and culture). This thesis aims to compare the effects of organic farming practices on soil physical, chemical and hydrological properties in relation to conventional farming systems. The research combines data from three different scales: field measurements, plot measurements and catchment modelling. At the field scale: 16 pairs of farms (organic and conventional between 50 and 3000 m apart) located in England, over a range of soil textures: clayey, silty, medium and coarse were investigated. There were also two different land uses (grass and winter wheat). Data was obtained on soil properties including: shear strength, Atterberg limits, field capacity, aggregate stability, HOST values, infiltration rates and Soil Organic Carbon (SOC). The analysis of the data shows that, whilst it is possible to detect the effects of both soil texture and land use (grassland / arable) on a number of the soil properties; there is no evidence that organic farming improves soil properties or physical condition - equally there is no detrimental effect. This is in agreement with the results of a number of other European studies. There was evidence to show that infiltration rates are greater on organically managed grassland than conventional grassland; which agrees with the HOST analysis where fewer fields were degraded under organic management. Fewer traces of pesticides and herbicides were in the soil water from the organic fields compared with the conventionally managed fields; none were at a level which would contribute to agricultural pollution. Cont/D.
  • Thumbnail Image
    ItemOpen Access
    Evidence for functional state transitions in intensively-managed soil ecosystems
    (Nature Publishing Group, 2018-08-01) Todman, Lindsay C.; Fraser, F. C.; Corstanje, Ronald; Harris, Jim A.; Pawlett, Mark; Ritz, Karl; Whitmore, Andrew P.
    Soils are fundamental to terrestrial ecosystem functioning and food security, thus their resilience to disturbances is critical. Furthermore, they provide effective models of complex natural systems to explore resilience concepts over experimentally-tractable short timescales. We studied soils derived from experimental plots with different land-use histories of long-term grass, arable and fallow to determine whether regimes of extreme drying and re-wetting would tip the systems into alternative stable states, contingent on their historical management. Prior to disturbance, grass and arable soils produced similar respiration responses when processing an introduced complex carbon substrate. A distinct respiration response from fallow soil here indicated a different prior functional state. Initial dry:wet disturbances reduced the respiration in all soils, suggesting that the microbial community was perturbed such that its function was impaired. After 12 drying and rewetting cycles, despite the extreme disturbance regime, soil from the grass plots, and those that had recently been grass, adapted and returned to their prior functional state. Arable soils were less resilient and shifted towards a functional state more similar to that of the fallow soil. Hence repeated stresses can apparently induce persistent shifts in functional states in soils, which are influenced by management history.
  • Thumbnail Image
    ItemOpen Access
    Evidence of ecological critical slowing-down in temperate soils
    (EGU: European Geophysical Union, 2022-05-27) Fraser, Fiona; Corstanje, Ronald; Todman, Lindsay; Bello-Curás, Diana; Bending, Gary; Deeks, Lynda K.; Harris, Jim A.; Hilton, Sally; Pawlett, Mark; Zawadzka, Joanna Ewa; Whitmore, Andrew P.; Ritz, Karl
    The resilience of ecological systems is crucially important, particularly in the context of climate change. We present experimental evidence of critical slowing-down arising from perturbation of a key function in a complex ecosystem, exemplified by soil. Different behavioural classes in soil respiratory patterns were detected in response to repeated drying:rewetting cycles. We characterised these as adaptive, resilient, fragile or non-resilient. The latter involved increasing erratic behaviour (i.e. increasing variance), and the propagation of such behaviour (i.e. autocorrelation), interpreted as a critical slowing-down of the observed function. Soil microbial phenotype and land-use were predominantly related to variance and autocorrelation respectively. No relationship was found between biodiversity and resilience, but the ability of a community to be compositionally flexible rather than biodiversity per se appeared to be key to retaining system function. These data were used to map the extent to which soils are close to crossing into alternative stable states at a national scale.
  • Thumbnail Image
    ItemOpen Access
    Facilitating the elicitation of beliefs for use in Bayesian Belief modelling
    (Elsevier, 2019-12-01) Hassall, Kirsty L.; Dailey, Gordon; Zawadzka, Joanna Ewa; Milne, Alice E.; Harris, Jim A.; Corstanje, Ronald; Whitmore, Andrew P.
    Expert opinion is increasingly being used to inform Bayesian Belief Networks, in particular to define the conditional dependencies modelled by the graphical structure. The elicitation of such expert opinion remains a major challenge due to both the quantity of information required and the ability of experts to quantify subjective beliefs effectively. In this work, we introduce a method designed to initialise conditional probability tables based on a small number of simple questions that capture the overall shape of a conditional probability distribution before enabling the expert to refine their results in an efficient way. These methods have been incorporated into a software Application for Conditional probability Elicitation (ACE), freely available at https://github.com/KirstyLHassall/ACE Hassall (2019)
  • No Thumbnail Available
    ItemOpen Access
    Interactions between tillage energy soil structural stability and organic matter
    (Cranfield University, 2003-11) Watts, Christopher W.; Godwin, R. J.; Spoor, Gordon; Whitmore, Andrew P.
    In agricultural production, disturbance of the soil by cultivation occurs regularly. Mechanical energy applied in this way can have a adverse effect on soil stability, a lowering of soil organic matter (S_OM), and a increase in CO2 emissions. These changes result in unwanted environmental consequences and compromise the ability of soil to maintain a competitive and sustainable agricultural industry. As agricultural systems evolve, it becomes important to develop a indication of their sustainability with regard to soil structure, well before any serious consequences become apparent. The am of this work was to quantify the effect of mechanical energy (in particular tillage) on soil structural stability and the loss of SOM. New laboratory techniques were devised in which mechanical energy was applied to a range of soils at different water contents with measurements made of stability and the mineralization of SOM. Techniques used for characterising stability involved measuring mechanically-dispersed clay, cm using a turbid metric technique and the proportion of water stable aggregates (>250 m). A re-examination of the statistical theory of brittle fracture showed that soil friability, F1, could be quantised using the coincident of Variation of tensile-strength of a population of similar sized aggregates. Specific energies associated with different cultivation practices, were simulated using a falling weight and results indicated that the sensitivity of soil to mechanical damage was essentially zero at soil water contents below the plastic limit (wpL). With increasing soil water content, sensitivity to destabilization increased sharply. The empirical model to characterise these phenomena was evaluated under field conditions where the energy consumption of different tillage implements, operating at different soil water contents, was measured directly. Good agreement between the level of destabilization measured in the field and those in the laboratory was obtained at similar specific energy values. C.W. Watts, 2003. Cranfield University, Silsoe. The field experiments also showed that increased levels of cm following tillage were responsible for stronger and less friable day aggregates. More experiments on a soil with SOC values ranging from all to 32 g/kg enabled the original model to be refined, linking cm, SOC and soil water content to disruptive energy. This led to the development of a index, S, which quantise the sensitivity of soil to destabilization by mechanical energy inputs and provides a method for identifying soils at risk. The effect of mechanical energy on the mineralization of SOC was measured using the falling-weight. Mineralization was characterised by measuring soil respiration using data-logging, conductinetric respirometers, built to monitor CO2 emissions following applications of mechanical energy. Changes in respiration were characterised by the respiration ratio, rr (defied a respiration following the application of energy divided by basal respiration). Higher values of, rr, were associated with greater energy levels, particularly on soils with lower SOC. Increased respiration was also measured following tillage in the field, particularly from soils following tillage at high energy levels where the effect lasted for several weeks. In this work three physically based measures of soil quality (S, F1 and rr) have been used to quantify the effects of tillage of different intensities on soil structural stability and the loss of organic matter. Parameters common to these measures of soil quality are SOC content, soil-water content and tillage intensity. Results of this work indicate that organic matter, physically protected by stable soil structures, can b exposed to mineralization when the structure in destabilized during tillage, particularly a the soil becomes wetter (w>w1ºL). The practical consequences of this work concluded that increasing the levels of SOC, cultivating the soil at water contents below the plastic limit and a reduced energy input, provide the best practical approach to maintaining soil physical quality. The new methodologies developed here have helped improve understanding of the effects of mechanical energy on soil structural condition. They provide a sound basis to answer a range of questions relating to soil physical quality and the consequences of different soil management practices for soil behaviour in the environment, thus enabling the boundaries between good and bad practices to b better defied.
  • Thumbnail Image
    ItemOpen Access
    Is it possible to increase the sustainability of arable and ruminant agriculture by reducing inputs?
    (Elsevier, 2009-02-01) Glendining, Margaret J.; Dailey, A. Gordon; Williams, Adrian G.; van Evert, Frits Kvan; Goulding, Keith W. T.; Whitmore, Andrew P.
    Until recently, agricultural production was optimised almost exclusively for profit but now farming is under pressure to meet environmental targets. A method is presented and applied for optimising the sustainability of agricultural production systems in terms of both economics and the environment. Components of the agricultural production chain are analysed using environmental life-cycle assessment (LCA) and a financial value attributed to the resources consumed and burden imposed on the environment by agriculture, as well as to the products. The sum of the outputs is weighed against the inputs and the system considered sustainable if the value of the outputs exceeds those of the inputs. If this ratio is plotted against the sum of inputs for all levels of input, a diminishing returns curve should result and the optimum level of sustainability is located at the maximum of the curve. Data were taken from standard economic almanacs and from published LCA reports on the extent of consumption and environmental burdens resulting from farming in the UK. Land-use is valued using the concept of ecosystem services. Our analysis suggests that agricultural systems are sustainable at rates of production close to current levels practiced in the UK. Extensification of farming, which is thought to favour non-food ecosystem services, requires more land to produce the same amount of food. The loss of ecosystem services hitherto provided by natural land brought into production is greater than that which can be provided by land now under extensive farming. This loss of ecosystem service is large in comparison to the benefit of a reduction in emission of nutrients and pesticides. However, food production is essential, so the coupling of subsidies that represent a relatively large component of the economic output in EU farming, with measures to reduce pollution are well-aimed. Measures to ensure that as little extra land is brought into production as possible or that marginal land is allowed to revert to nature would seem to be equally well-aimed, even if this required more intensive use of productive areas. We conclude that current arable farming in the EU is sustainable with either realistic prices for products or some degree of subsidy and that productivity per unit area of land and greenhouse gas emission (subsuming primary energy consumption) are the most important pressures on the sustainability of farming.
  • Thumbnail Image
    ItemOpen Access
    Putting numbers to a metaphor: a Bayesian Belief Network with which to infer soil quality and health
    (Elsevier, 2025-07) Hassall, Kirsty L.; Zawadzka, Joanna Ewa; Milne, Alice E.; Corstanje, Ronald; Harris, Jim A.; Dailey, A Gordon; Keith, Aidan M.; Glendining, Margaret J.; McGrath, Stephen P.; Todman, Lindsay C.; Alexander, Paul; Arnold, Philippa; Bennett, Amanda J.; Bhogal, Anne; Clark, Joanna M.; Crotty, Felicity V.; Horrocks, Claire; Noble, Nicola; Rees, Robert; Shepherd, Matthew; Stockdale, Elizabeth A.; Tipping, Edward W.; Whitmore, Andrew P.
    Soil Quality or Soil Health are terms adopted by the scientific community as metaphors for the effects of differing land management practices on the properties and functions of soil. Because they are metaphors, consistent quantitative definitions are lacking. We present here an approach based on expert elicitation in the field of soil function and management that offers a universal way of putting numbers to the metaphor. Like humans, soils differ and so do the ways in which they are understood to become unhealthy. Long-term experiments such as the Broadbalk Wheat experiment at Rothamsted provide unparalled sources of data with which to investigate the state and changes of soil quality and health that have developed from known management over timescales of one hundred years or more. Similarly, large-scale datasets such as the National Soils Inventory and Countryside Survey provide rich resources to explore the geographical variability of soil quality and health in different places against a background of different observed management practices. We structure experts’ views of the extent to which soil delivers the functions expected of it within Bayesian Belief Networks anchored by measurable properties of soil. With these networks, we infer the likely state of soil (i) on Broadbalk, (ii) at locations throughout England & Wales as well as inferring (iii) the most straightforward ways of improving soil quality and health at the locations in (ii). Our methodology has general applicability and could be deployed elsewhere or in other disciplines.
  • Thumbnail Image
    ItemOpen Access
    Technologies for increasing carbon storage in soil to mitigate climate change
    (Wiley, 2015-10-01) Whitmore, Andrew P.; Kirk, Guy J. D.; Rawlins, Barry G.
    Means to enhance storage of carbon in soil or avoid its loss from soil are discussed and examined from the viewpoint of policy. In particular, technologies that have until now received little attention are assessed. The main means by which soil carbon might be increased are first listed. These are the following: (i) increasing the rate of input of organic matter; (ii) decreasing the rate of its decomposition by biological or chemical means; (iii) increasing the rate of its stabilization by physico-chemical protection within aggregates and organo-mineral complexes; and (iv) increasing the depth or more correctly the total soil volume sequestering carbon at maximum rate. Immediate gains in carbon storage might be made by switching to more perennial crops, especially grasses that, as a result of breeding, are able to put more carbon into soil. In the longer term, targets for research such as understanding the role of enzymes in carbon turnover and the exploitation of the capacity in subsoils are suggested. Increased fixation of CO2 as inorganic carbonate in soils by application of silicate wastes may have some role.
  • Thumbnail Image
    ItemOpen Access
    What do we need to know to enhance the environmental sustainability of agricultural production? A prioritisation of knowledge needs for the UK food system
    (MDPI, 2013-07-17T00:00:00Z) Dicks, Lynn V.; Bardgett, Richard D.; Bell, Jenny; Benton, Tim G.; Booth, Angela; Bouwman, Jan; Brown, Chris; Bruce, Ann; Burgess, Paul J.; Butler, Simon J.; Crute, Ian; Dixon, Frances; Drummond, Caroline; Freckleton, Robert P.; Gill, Maggie; Graham, Andrea; Hails, Rosie S.; Hallett, James; Hart, Beth; Hillier, Jon G.; Holland, John M.; Huxley, Jonathan N.; Ingram, John S. I.; King, Vanessa; MacMillan, Tom; McGonigle, Daniel F.; McQuaid, Carmel; Nevard, Tim; Norman, Steve; Norris, Ken; Pazderka, Catherine; Poonaji, Inder; Quinn, Claire Helen; Ramsden, Stephen J.; Sinclair, Duncan; Siriwardena, Gavin M.; Vickery, Juliet A.; Whitmore, Andrew P.; Wolmer, William; Sutherland, William J.
    Abstract: Increasing concerns about global environmental change and food security have focused attention on the need for environmentally sustainable agriculture. This is agriculture that makes efficient use of natural resources and does not degrade the environmental systems that underpin it, or deplete natural capital stocks. We convened a group of 29 ‘practitioners' and 17 environmental scientists with direct involvement or expertise in the environmental sustainability of agriculture. The practitioners included representatives from UK industry, non-government organizations and government agencies. We collaboratively developed a long list of 264 knowledge needs to help enhance the environmental sustainability of agriculture within the UK or for the UK market. We refined and selected the most important knowledge needs through a three-stage process of voting, discussion and scoring. Scientists and practitioners identified similar priorities. We present the 26 highest priority knowledge needs. Many of them demand integration of knowledge from different disciplines to inform policy and practice. The top five are about sustainability of livestock feed, trade-offs between ecosystem services at farm or landscape scale, phosphorus recycling and metrics to measure sustainability. The outcomes will be used to guide ongoing knowledge exchange work, future science policy and funding.