Innovations in soil science to address global grand challenges

This Special Issue presents a collection of papers commissioned to celebrate the UK Centre for Doctoral Training (CDT) in soil science known as 'STARS' (Soils Training And Research Studentships). The collection was written by emerging scientists and their collaborating supervisory teams. The call for papers was principally aimed at STARS students, but submissions were also encouraged from students in the wider UK soils community, who are also represented. The STARS CDT was originally commissioned in 2015 as part of a funding collaboration between the UK Natural Environment Research Council and the UK Biotechnology and Biological Science Research Council (BBSRC). The paper by Haygarth et al. (2021) provides a reflection on the STARS CDT experience, exploring what can be learnt from the new pedagogic approach. It describes how a discipline-focussed doctoral centre is a novel and unique way of teaching and learning soil science, proposing that this might be a model for future post graduate soil science teachers to learn from, in order to continually improve and innovate in the way we train our PhD students. In total, the Special Issue contains 17 papers, of which 15 appear in hard copy (incidentally, the last hard copy issue of the European Journal of Soil Science before conversion to solely on-line publication). All but one of the papers (Haygarth et al., 2021) are student-led, with three by non-STARS students (Jonah Prout, Yan Ma and Melanie Armbruster). The papers loosely fall into three categories: (1) Those involving local-scale controlled experiments and method development (seven papers), (2) those focussed on empirical analyses of large-scale datasets (six papers) and (3) those that involve a meta-analyses of previously published literature (three papers). In the first category, Chris McCloskey contributes two papers as lead author. In the first paper (McCloskey et al., 2020), a field system is presented for measuring plant and soil carbon fluxes using stable isotope methods, with sufficient precision to resolve diurnal and seasonal patterns. In the companion paper, the field system is used to demonstrate the importance of allowing for transient variation in plant and soil δ13C end members in partitioning fluxes from net ecosystem respiration (McCloskey et al., 2021). Ma et al. (2021) assessed the relative efficacy of nitrification inhibitors in a highly nitrifying soil and, like McCloskey, used carbon-labelling techniques to help achieve this. Dan Evans takes us to the core of soil formation, using a new technique of cosmogenic radionuclide analysis (Evans et al., 2021) with a conclusion that questions the accuracy of our existing soil formation knowledge, arguing that we must consider the bulk density profile of the overlying soil. At a slightly larger scale, 'Bee' Burak et al. (2020) uses an inductive mesocosm-based assessment to study how root hairs affect soil erosion by simulated rainfall. In similar controlled conditions, Corina Lees et al. (2020) used a growth room to control her climate change study in selecting plant traits for soil erosion control in grassed waterways. Marta Cattin et al. (2021) also uses controlled conditions with a 21-day laboratory microcosm incubation in order to assess the fate of soil carbon following the application of anaerobic digestate. In the second category, Fiona Seaton et al. (2020) uses an empirical data-driven analysis based on national (Welsh) monitoring of soil indicators to reflect on soil health, using large-scale data analyses (over 1350 topsoils) to understand the state and change of soils at a national scale. Her work shows the importance of land-use management in determining the soil health and functional capacity of soils. In an empirical approach not dissimilar, Armbruster et al. (2020) has a focus on bacterial and archaeal taxa as potential indicators of soil restoration across grasslands. The work highlights that microbial taxon are among the most sensitive indicators of soil restoration. Paul George et al. (2020) studied anaerobes and sulphate-reducing bacteria in relation to pH across varied land uses, using a nationwide 'metabarcoding' dataset from 436 sites belonging to seven contrasting temperate land uses. Andrew Tweedie et al. (2021) tested the hypothesis that phosphorus forms and functions in agricultural soils have changed over a period of 50–70 years, using topsoils from 35 agricultural sites in Northeast Scotland, compared at 'original' and 'resampled' timepoints. The paper by Hannah Cooper (2021) uses a broadly similar 'long-term' sampling approach and considers how long-term zero-tillage enhances the protection of soil carbon in tropical agriculture, studying soil samples collected from experimental fields in Botucatu, Brazil, which had been under zero-tillage for 2, 15 and 31 years. The paper by Prout et al. (2020) focusses on soil organic matter and proposes an index approach based on organic carbon-to-clay ratio. Again, like the above papers this work was empirically based, using 3809 sites from the National Soil Inventory of England and Wales. In the third category, Harry Barrat studied the impact of drought and rewetting on nitrous oxide emissions from soil in temperate and Mediterranean climates (Barrat et al., 2020). The method used the first meta-analysis and synthesis of the literature. Anchen Kehler et al. (2021) also applied a literature-based approach to her work, trying to predict how soil phosphorus will react to climate change. Finally in a wonderful collaborative article between the STARS students, Mihai Cimpoiasu et al. (2021) was first author on a reflective consideration of future priorities for soil science: 'Comparing perspectives from scientists and stakeholders'. Soil science has never seemed so topical, providing services underpinning our existence (Haygarth & Ritz, 2009) while addressing sustainable development and global grand challenges (Lal et al., 2021). It is thus timely to see this collection led by early career scientists on Innovations in Soil Science to Address Global Grand Challenges. Moreover, it is encouraging, not only because of the diversity of research findings themselves, but because of the promise it shows for our future capacity to deliver the discipline. Data sharing is not applicable to this article as no new data were created or analyzed in this study.