Browsing by Author "Mooney, Sacha J."
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Item Open Access A new theory for soil health(Wiley, 2022-07-26) Harris, Jim A.; Evans, Daniel L.; Mooney, Sacha J.The term “soil health” has captured the interest of government, and land managers, whilst the academic community has struggled to rationalise its use and wider benefit. It has proved a powerful tool in conveying best practice to a lay audience. However, the widespread adoption of the “metaphor” has resulted in calls for tools that facilitate the measurement of soil health, preferably quantitatively, and often as a single figure, for ease of use/communication and cost of monitoring. The insurmountable problem is that soil health is neither a readily quantifiable nor measurable object. Only organisms can have ‘health’, which manifests as characteristics of a living system—true of complex systems exhibiting “emergent” properties such as resilience in the face of perturbation. We pose the key question: is soil really a system capable of exhibiting “health”, or any other property emerging from a complex, connected, self-regulating system? We argue that if you cannot detect emergent properties, you are: (i) looking at the wrong dynamic parameter; (ii) not considering the entire system; or (iii) not evaluating at a system at all. We suggest that our focus should instead be on the relationships between components, complexity, and function. Using this as a basis for a new framework will allow us to assemble and align disparate threads of soil science into a cogent and coherent “new theory of soil health”, which is an essential and practical step forward for the sustainable management of global soil resources, across all land uses.Item Open Access On pedagogy of a Soil Science Centre for Doctoral Training(Wiley, 2021-10-13) Haygarth, Philip M.; Lawrenson, Olivia; Mezeli, Malika; Sayer, Emma J.; McCloskey, Christopher S.; Evans, Daniel L.; Kirk, Guy J. D.; Tye, Andrew M.; Chadwick, David R.; McGrath, Steve P.; Mooney, Sacha J.; Paterson, Eric; Robinson, David A.; Jones, Davey L.Here we describe and evaluate the success of a multi-institutional Centre for Doctoral Training (CDT), which was established to address a UK skills shortage in Soil Science. The government-funded ‘STARS’ (Soils Training And Research Studentships) CDT was established in 2015 across a range of universities and research institutes in the UK. It recruited 41 PhD students equitably split across the institutions under four core research themes identified as being central to the national need, namely, (1) Understanding the soil–root interface, (2) Soils and the delivery of ecosystem services, (3) Resilience and response of functions in soil systems and (4) Modelling the soil ecosystem at different spatial and temporal scales. In addition, the STARS CDT provided a diverse skills programme, including: Holistic training in soils, the promotion of collegiality and joint working, strategies to promote science and generate impact, internships with end users (e.g., policymakers, industry), personal wellbeing, and ways to generate a lasting soils training legacy. Overall, both supervisors and students have reported a positive experience of the CDT in comparison to the conventional doctoral training programmes, which have less discipline focus and little chance for students to scientifically interact with their cohorts or to undertake joint training activities. The STARS CDT also allowed students to freely access research infrastructure across the partner institutions (e.g., long-term field trials, specialised analytical facilities, high-performance computing), breaking down traditional institutional barriers and thus maximising the students' potential to undertake high-quality research. The success and legacy of the STARS CDT can be evidenced in many ways; however, it is exemplified by the large number and diversity of journal papers produced, the lasting collaborations, final career destinations, and creation of a web-based legacy portal including new and reflective video material.Item Open Access Soil seal development under simulated rainfall: structural, physical and hydrological dynamics(Elsevier, 2017-11-01) Armenise, Elena; Simmons, Robert W.; Ahn, Sujung; Garbout, Amin; Doerr, Stefan H.; Mooney, Sacha J.; Sturrock, Craig J.; Ritz, KarlThis study delivers new insights into rainfall-induced seal formation through a novel approach in the use of X-ray Computed Tomography (CT). Up to now seal and crust thickness have been directly quantified mainly through visual examination of sealed/crusted surfaces, and there has been no quantitative method to estimate this important property. X-ray CT images were quantitatively analysed to derive formal measures of seal and crust thickness. A factorial experiment was established in the laboratory using open-topped microcosms packed with soil. The factors investigated were soil type (three soils: silty clay loam - ZCL, sandy silt loam - SZL, sandy loam - SL) and rainfall duration (2-14 minutes). Surface seal formation was induced by applying artificial rainfall events, characterised by variable duration, but constant kinetic energy, intensity, and raindrop size distribution. Soil porosities derived from CT scans were used to quantify the thickness of the rainfall-induced surface seals and reveal temporal seal micro-morphological variations with increasing rainfall duration. In addition, the water repellency and infiltration dynamics of the developing seals were investigated by measuring water drop penetration time (WDPT) and unsaturated hydraulic conductivity (Kun). The range of seal thicknesses detected varied from 0.6 - 5.4 mm. Soil textural characteristics and OM content played a central role in the development of rainfall-induced seals, with coarser soil particles and lower OM content resulting in thicker seals. Two different trends in soil porosity vs. depth were identified: i) for SL soil porosity was lowest at the immediate soil surface, it then increased constantly with depth till the median porosity of undisturbed soil was equalled; ii) for ZCL and SL the highest reduction in porosity, as compared to the median porosity of undisturbed soil, was observed in a well-defined zone of maximum porosity reduction c. 0.24 - 0.48 mm below the soil surface. This contrasting behaviour was related to different dynamics and processes of seal formation which depended on the soil properties. The impact of rainfall-induced surface sealing on the hydrological behaviour of soil (as represented by WDTP and Kun) was rapid and substantial: an average 60% reduction in Kun occurred for all soils between 2 and 9 minutes rainfall, and water repellent surfaces were identified for SZL and ZCL. This highlights that the condition of the immediate surface of agricultural soils involving rainfall-induced structural seals has a strong impact in the overall ability of soil to function as water reservoir.