Part 1: Soil Judging
In June, I was incredibly lucky to be part of TeamGB who represented Great Britain at the 5th International Soil Judging Contest, held in the week before the 23rd World Soils Congress in Nanjing, China. I wish I could say that I was a worthy participant, but the truth is it was the first time that I had heard of soil judging and was far from ready or experienced. However, it was one of the most intense learning experiences of my life, made me excited about understanding and teaching soil, and I think provided a model of how to teach technical topics. Eighteen countries sent teams. The United States, who treat this discipline with the seriousness other nations reserve for the Olympics, were favourites. TeamGB, entering for the first time, was not.
We were based in a hotel on the outskirts of Nanjing, once China’s historic capital, now a sprawling modern city on the Yangtze River, surrounded by paddy fields that had been worked and shaped for thousands of years, their soils laid down by silt from the Yangtze floodplain and reworked ever since by humans forming and reforming terraces and drainage channels to control the water for paddy rice. That was the technical backdrop for the competition.
The first part of the week was classroom-based and academic, the lecture theatre a short ride from the hotel at the Chinese Academy of Soil Science: a cavernous hall built, by the look of it, for an audience several times the size of our group of one-hundred-and-something soil judgers. One morning, we went to the newly finished soil museum, organised especially in time for the congress. The museum inside was amazing, well-lit but with a warm glow, and a backdrop of shades of grey, cleverly planned I think to make photographs look great, like some sort of sci-fi techno futurist world of soil. The museum had full soil profiles from across China, several metres deep, framed and somehow set with resin and hung on the wall like geological art. I have no idea how it’s done, but it looked good enough that I made a note we should find out and try something similar for Eurosoil 2028 in Scotland.
The latter part of the week was spent in the field, practising pits and building towards the final day: the grand competition. The training was built around repetition, which turns out to be very clever. Mornings were classroom, afternoons were field, and by Thursday we had dispensed with the classroom altogether. Friday was a full practice run across four pits ahead of the actual competition on Saturday.
We had spent the week taking what felt like thousands of photographs of each other in muddy holes, and in the evenings we would organize photographs and recounting the day’s events for the evening in short dispatch back to Ella at BSSS HQ, who was doing an amazing job of turning our hurried notes and pictures into something resembling a social media presence for British soil judging, which more than once, made us look rather more put-together than we felt.
For the field work, each morning, after thirty minutes or so on one of the four yellow buses, we would disembark and orientate ourselves at a pre-dug pit. It was at this point I usually realised I had forgotten some key piece of equipment, though luckily, we had Cairo on the team. Cairo was a cross between Dora the Explorer and the SAS, carrying three separate backpacks and, whatever the problem turned out to be, Cairo seemed to have whatever was needed – she was our unofficial quartermaster, without whom we would have struggled considerably.
The pits themselves are typically dug some two metres into the earth with a marked face on one side. You are given a little over an hour to do two things: describe the soil in front of you, firstly defining the horizons and bounds, using texture, colour and structure, supplemented by a card of laboratory results and a few clues from the judges, and then classify it according to one of the major international systems.
Texturing the soil by hand was the part I struggled with most, so on team exercises we leant heavily on Jess, who grew up on a farm on the Moray Coast and has an intuition for soil the rest of us spent the week trying to catch up with; Jess could accurately texture a clay to within a percent or two by feel alone. Ours were generally heavy silty clays and clay loams, baked hard by a week of thirty-degree heat, and getting a sample to ribbon properly between finger and thumb takes more practice than I had behind me. I think for future TeamGB soil judging, an amazing practice would be to get an electronic scale and some bags of sand, silt and clay, and create different soil types from scratch and practice texturing them. This is the sort of thing we could easily do in the Cranfield soil laboratory.
What we were looking at, pit after pit, was paddy soil: the accumulated evidence of several thousand years of rice cultivation, turned out to be reflected in the shades of grey and red and how they changed through the layers. Waterlogging does something specific to soil chemistry, and most of the week was spent learning to read it. Iron either leaves a profile, leaving pale grey patches where oxygen cannot reach, or it concentrates into rust-coloured mottles and nodules where it can. The effect along pores or old root channels also provided a clue. Telling these features apart and working out which feature was inside or outside of the aggregates, turned out to be the key to unlock the history of these soils. Theo, newest to soil science of all of us and only just starting his PhD at Reading, quietly became the team’s technical expert on redoximorphic features, and towards the end of the week was really starting to nail it.
Over the course of the week, you do this roughly a dozen times, which means you get to be wrong in roughly a dozen different ways and have someone explain why before lunch. It is one of the more efficient ways of learning soil science I have come across, and whilst hard work, much more effective than the classroom.
On competition day, the shift in atmosphere was immediate: phones disappeared, the light-hearted banter between teams fell away, and contact with coaches ceased for the duration of the four pits, leaving just the four of us together, without Jay, for the first time. It was then that we truly appreciated everything she had done. Beyond being an expert soil judge from Australia, Jay was deeply embedded in the global soil judging community and had spent several years working to bring TeamGB together. Alongside Richard Hewison at the Hutton, she had ensured we received both hands-on training in the UK and online preparation, doing everything in their power to set TeamGB up for success long before we ever saw a pit.
Competition day itself proved to be a wonderful experience, particularly the team event. We settled into our agreed roles and grew steadily in confidence, so much so that on the final team pit we finished our classification with five minutes to spare, something that would have seemed impossible just days before.
The results were read out at a dinner on the final night, with enough Chinese food and beer to make the placing feel entirely beside the point. Despite our improvement over the week, TeamGB finished some way outside the medals, which surprised nobody – we had entered this year mainly to find out what we didn’t know, and there was a great deal of it. The USA teams won as everyone expected, on the strength of a selection system that runs thousands of students through regional and national competitions before sending the best eight abroad. However, the German team had a very impressive placing too.
What struck me more than the result was the culture around it. Soil judging appears to run on an informal but widely respected rule that once you’ve had your turn at the top, you step aside for the next cohort, which is presumably why most of the room, regardless of nationality, was made up of people doing this for the first time, us included. By then we had genuinely bonded as a team, despite having known each other for only a few days. If the four of us manage nothing else, we share a determination that a future TeamGB turns up at the next one too, better prepared, with a good chance of placing, but more importantly with future generations who share our passion for describing and classifying soil.
Part 2: World Congress of Soil Science.
The following week, soil judging gave way to the World Soils Congress proper. The conference programme arrived as a four-hundred-page PDF organised by neither time nor place, and the venue was vast enough that some sessions were a quarter of an hour’s walk apart. I quickly learnt that, whilst I put considerable time into planning my schedule, it was generally better to embrace whatever session I happened to be in at the time, as the complexity and logistics of moving around for specific sessions was too emotionally and intellectually draining.
Among the few technical ideas, I’ll bring home: biochar appears to reduce soil acidity in a way that nudges microbial pathways towards ammonium rather than nitrate, which in turn means less N2O and better nitrogen use efficiency – a connection Pete Smith illustrated with biochar soaked in urine, used in parts of Africa as a slow-release nitrogen source which I should look into. Prof Deli Chen’s group at Melbourne, including a researcher named Baobao, presented a very relevant machine-learning model to predict nitrification; I asked whether it might one day be made available as an API, an idea that hadn’t occurred to them but was received warmly, and we agreed I would send some data over to see what their model makes of it. There was, somewhat to my surprise, little or nothing on carbon calculators, a live topic at Cranfield just now, and less on process-based modelling and regenerative agriculture than I’d anticipated, though that may say more about British preoccupations than global ones. There was also very little on tea, my own subject: mine was one of perhaps a handful of tea-related talks across the entire programme. The poster hall had almost nothing on the subject either – I had vowed to read every poster, but at nearly a thousand to get through, the best I could hope for was to read each title, and zoom into the most interesting. My best guess is that the scientists working on tea in China are publishing as soil chemists or microbiologists rather than as tea scientists, so the discipline doesn’t show up under its own name.
My own talk fell in the greenhouse gas session on the Thursday, covering Cranfield’s work on N2O emissions from tea soils in Kenya. I’d written fifteen minutes of material and was given eight, which meant cutting everything non-essential and speaking at a pace that assumed the audience already knew roughly what I was talking about. After my talk, I was approached by one person: a researcher working on annual crops, interested less in tea than in the fertiliser types we’d tested.
Thankfully, Jess, who also chairs the BSSS Early Careers committee, had organised perhaps ten of us into a WeChat group, which provided a welcome thread of familiarity through four days otherwise spent navigating a building the size of a small town. A handful of soil judging competitors from other countries showed up too, though fewer than I’d expected.
Part 3: The ‘Scientific Expedition’.
The congress ended on the Friday, and with it came the final phase: an optional four-day post-conference tour billed as a “Scientific Expedition” through the tea and rice soils of Hangzhou. China is where tea cultivation began, and still grows and consumes more than any other country. My own PhD research at Cranfield modelling nitrogen and greenhouse gases in tea is based thousands of miles away in the tea fields of western highlands of Kenya, agronomically among the best tea-growing land anywhere. But, this trip was a chance to see where it all started.
The high-speed train to the tea area of Hangzhou took about two hours, the entire route lined on one side by small, ancient paddies and on the other by tower blocks that seemed never to end. I shared the carriage with Tobias, part of Germany’s rather more successful soil judging team, who had studied in Munich under soil judging legend Peter Schad (who himself was on an alternative tour to the Loess Plateau). Tobias and I talked about where China’s large scale commercial agriculture must be since it clearly wasn’t here, as well as the Loess Plateau and soil issues there, and at some point, the conversation drifted onto our own work. Tobias is building a denitrification module into the DAISY model at the University of Copenhagen; I am trying to do much the same thing in a Cranfield tea model. We spent a fair part of the journey, and a fair part of a hotel evening some days later, comparing notes, and I hope we find a way to collaborate in future.
It became apparent within about half a day that “Scientific Expedition” was, at best, an aspirational title. The first day and a half delivered a lake, a shopping street and several temples, all genuinely pleasant, but not remotely what fifteen soil scientists had cleared their diaries for. There was nothing to be done about it once the coach had set off, so the fifteen of us accepted our fate as somewhat unwilling tourists, and not a further complaint was heard. Remarkably, this shared disappointment turned out to be the making of the trip. The bus journeys were where the real bonding happened: my bus friend was a Polish professor of earthworms who, it turned out, dresses entirely in shades of pink – one shade, she explained, for each species of earthworm native to Poland. We talked at length about worms, which I had not expected to be one of the more interesting conversations of the trip, and which turned out to be exactly that.
The tea part of the trip came on the second afternoon, and was, for me, the only part I had really come for. It started with a visit to China’s tea museum, cut short at a brisk forty minutes by a guide who seemed faintly unable to understand why anyone would want longer. The tea soils came next (what I had most looked forward to) though this turned out to be a stylised tourist attraction built around the idea of a tea village rather than a working one. When the guide began listing the world leaders who had visited, I suspected soil scientists were about to be disappointed. We arrived at some unremarkable tea plants overlooking an artificial looking “tea village,” where a local professor stood beside a hastily scraped bank of terraced soil with a tape measure. He gave us a short introduction. I asked how the landscape had formed; he told me he wasn’t sure, though I would guess tectonic uplift, or simple hydrological weathering. Moments later, and seemingly on cue, a man arrived with a petrol-powered pruning machine and began trimming the bushes immediately beside us, and we were ushered away on the grounds that it was, undeniably, too noisy to continue (as a student of tea myself, I can think of no reason to be pruning the tea bushes at that time, other than to keep the tour on schedule). A few of us lingered at the “pit” where one of the top soil judgers from the impressive Polish team, wanted to discuss the professor’s classification of the soil as an Acrisol, and suggested that due to the slope too steep and a clay horizon too absent, maybe was a Cambisol instead. We had ten minutes with the soil, after two days of waiting for it, and were then delivered to a tea house for what had been billed as afternoon tea and turned out to be a well-rehearsed sales pitch for some optimistically priced green tea.
That evening’s dinner was fun, and everyone started sharing stories of where they came from. Pedro, from a tiny Azorean island now working at Wageningen, told us about a village tradition involving a bull let loose through the streets while the brave (or foolish) villagers challenge it. Across the table, a softly-spoken soil scientist who had spent years studying the Galápagos casually asked whether anyone fancied collaborating on research out on the islands – the sort of invitation most scientists could only dream of. Meanwhile, Lefteris, a gregarious agriculturalist the same age as me, painted a picture of an idyllic mediterranean upbringing on a Greek island, and confirmed, when pressed, that the islanders really do sing and dance choreographed ABBA routines even when there are no cameras around.
On the final morning, in the rain, we visited a working paddy field with a pit dug to a metre and a half – the genuine article, mottled grey and rust from top to bottom, with a clear ploughpan beneath twenty centimetres of organic topsoil, and a classification, a Hydragric Anthrosol, that nobody felt moved to dispute. It was, by some distance, the most convincing soil of the entire trip, and it had taken until the very last morning to arrive. This was followed by a visit to a local agricultural research station, and an experience you can only have in China, a snack of pickled mustard root and chrysanthemum juice. Then, on to an afternoon at China’s answer to Venice, a place called Water Town: charming, but every bit as overrun with tourists as the name suggests. Somewhere along the route, one of the group turned out to have a natural gift for posing, and insisted on photographs at every canal and bridge; since I enjoy taking them, the two of us spent the best part of an hour working our way along the waterfront together, her in various poses and me working the camera, to the quiet amusement of everyone else on the tour.
As the rest of the group drifted off to a commercial coffee shop, a fellow second year PhD from Colorado State called John and I headed off to try to find a proper Chinese tea house instead. We found one on a back street, a wooden building with old rickety steps leading up to an open tea-room overlooking the canal. Over expensive but famous West Lake tea, two former soldiers, now soil scientists, ended up talking for the best part of an hour about tea and elk hunting. John told an amazing story of how he had recently taken down a large, mature cow by himself, field-dressed it on the spot, and then spent the day hauling around 100 kilograms of meat back out over many miles and two thousand feet of climbing.
We were eventually retrieved and ferried back for about 20 minutes by something resembling a gondola, passing newly married couples and graduating students in striking traditional dress, having their photographs taken along the water – apparently a popular pursuit among China’s growing middle class.
– Thomas Smith
