The Story So Far: North Wyke Field Site
North Wyke in Devon is one of our three ERW field sites, central to Work Package 1: Field Sites. As we’re part of the UK Greenhouse Gas Removal (GGR) Demonstrator programme, our field sites are a key part of the ‘demonstrating’ aspect. They demonstrate and test the impacts of basalt application on GGR, crop yield and soil fertility health. North Wyke is a Rothamsted Research facility plot that replicates lowland grazing via the production of silage allowing us to evaluate EW with this land use.
Since our Demonstrator programme has now been running since May 2021, we’re here to share the story so far on each of our research strands, beginning with our field sites. We’ll then seek to provide regular updates on what’s happening in each of these areas. So, how have things been progressing at North Wyke?
As our plot was used for a previous UKRI-BBSRC project, which has now ended, the plots were resown with rye grass and the N2-fixing legume for our project. For consistency in the material used in the experiments across our field sites, we’ve co-ordinated our order for crushed basalt rocks with Harpenden.
Our North Wyke team has met with project colleagues at Southampton to discuss sample numbers, storage and transfer protocols. We are building connectivity between the North Wyke and Southampton teams for discussion to resolve any uncertainties.
Extra clover has been sown on the plot – red clover AberClaret at a rate of 5 kg/ha. Clover is a typical nitrogen fixer in grazing systems.
Modifications to the plot since it was used for a separate field trial have now been completed. We’re letting the plot settle down and reverting our attention to our monitoring kit. Our first delivery of basalt is due on 16th September and will be stored securely inside a fertilizer store.
Our main focus has been reservicing the auto-samplers. We’re aiming for basalt application in spring – ideally in March or April. Some storm damage anticipated to solar panels.
All plots have now been sown with grass and clover mix, with good establishment and survival of the clover over the winter period. Our rock dust has been delivered, with samples sent to Oxford, Southampton and Sheffield for analysis, as part of Work package 1b, ‘Measuring weathering rates, CO2 removal and storage’.
The first set of soil samples was collected before any fertilizer or rock dust was applied to the plots, to act as a baseline reading for the rest of the experiment. The soils were collected from the surface to 30 cm depth, and then from 30 to 60 cm deep. We’ll sieve the samples and air dry them before sending them off to the labs for analysis.
We’ve installed the greenhouse gas (CO2, CH4 and N2O) chambers and collected the first pre-treatment run. We’re planning to apply the fertiliser around 19th April, with gas samples planned for the rest of 2022-23 season, and rock dust applied the 26th April. First soil samples have been collected, and hydrological equipment is planned to be in place and recording data before the crushed basal rock treatments applied. Our hydrological equipment records stage height (which is converted to runoff volume using a rating) at 1 minute intervals and also use autosamplers to collect water quality samplers during runoff events which are then taken to the labs for various analyses – including alkalinity, pH, metals, anions, nutrients, DOC and strontium isotope ratios.
We are in full swing! We applied crushed basalt to plots on 26th April, with greenhouse gas samples taken daily until 29th April, then weekly until 24th May and then fortnightly.
Our first cut silage was taken on 1st June. The plots were then re-fertilised with phosphorus and potassium on 9th June in preparation for the second cut of silage. This is a later cut than planned due to poor plant growth – it has been such a prolonged period of very dry weather (the sixth driest summer on record) that there is low soil water availability (basically, the ground is too dry for the plants to grow to the size they normally would). Herbage samples have been dried and milled in preparation for sending to the lab for forage quality analysis – so we can compare the quality of plants that would be grazed by farm animals. We’ve also sieved, dried and prepared our soil samples for sending to the lab for analysis.
To ensure consistency across our three field sites, the same basaltic rock dust is being used at all three sites in our programme – the others being UKCEH at Plynlimon, and Rothamsted Research at Harpenden – in late May for the weathering study. At North Wyke, rock dust was sieved to the correct particle size fraction, added to nylon mesh bags and buried in the plots in the week beginning 11th July, so that we can measure how much weathering has happened when we next dig up the bags.
There are some emerging research outputs: Adie Collins has been working on updating the Rothamsted Research CSM farm scale modelling framework with up-to-date (post-2019) land use (crop areas and associated management operations) and livestock (types, ages, counts) data at national scale for England. CSM is a modelling framework for assessing farm-to-landscape scale impacts of land use/management under a range of different scenarios.
We’ve been sharing our greenhouse gas flux calculator with the Harpenden field site too, to calculate flux from sample ppm values. We report our values for the three gases not as a concentration, but as an amount of each gas per hectare per day, with the flux calculator using measured values such as air temperature and pressure as well as constants such as the universal gas constant to perform the calculation. We then combine each of the three individual gases together to report a single carbon dioxide equivalent for the plots receiving rock dust as well as those that don’t get any rock dust applied, and over a year we will see if the application of the rock dust reduces the emission of greenhouse gases.
Great news: we are making real progress towards impact! CO2 from air as assessed by greenhouse gas samples (and accumulated CO2 over time) is lower in rock dust plots compared to the control plots, though the difference is not statistically significant. This means enhanced rock weathering is reducing soil efflux of carbon dioxide! No water has been sampled as yet due to the prevailing dry weather conditions, so we’re unable to comment on the movement of newly formed carbonates into drainage water just yet.
An exciting time for North Wyke with some potentially interesting results! We hope to hear more once the weather is less dry and more waters can be sampled. No doubt the rain will return in typical British fashion soon enough!
With many thanks to Prof Adie Collins for the help co-ordinating this blog
- Authored by Victoria Giordano-Bibby,
Research Centre Manager