Three thousand soil scientists, researchers, industry, and of course farmers, from the around the globe descended on the World Congress of Soil Science (WCSS), held in Glasgow in August. Glasgow’s enormous exhibition centre hosted five days of scientific and policy programmes, talks and workshops focused on soil science. There was also time for a few pints of Tennent’s and to sample a couple of Glasgow’s infamous curry houses!
Reasons to join in
I attended WCSS not just as a researcher to broaden my knowledge of soil science and experimental techniques. But also to bring new methods, analysis techniques and context to my own PhD work and other long-term soil and farming systems trials at Morley and across East Anglia. In addition, I went as a representative of the research being carried out in Norfolk supported by TMAF.
Soil science has become a lot more than spades and augers over recent years. Technologies such as X-ray CT scanning for assessing physical structure of the soil, satellites to measure crop performance and soil properties and DNA barcoding of soil biology all featured heavily at the conference. Through funding and support to researchers these techniques are also being used on trials and projects supported by TMAF, for example:
- Connecting soil health to crop performance: research findings
- Seeking solutions to subsoil compaction problems
- Investigating biophysical effects of living plant root systems on soil health and crop yields
Although extremely useful to researchers and the industry these techniques are currently either too expensive or not practical to be implemented widely to inform on farm management decisions.
Breaking new ground
For me, one of the most interesting talks of the conference was from Munisath Khandoker, a PhD student from Rothamsted. Munisath has been testing a smartphone mobile application for measuring aggregate stability against more traditional measures using samples from the long-term field experiments at Rothamsted. Soil aggregate stability affects erosion, infiltration, and plant root growth. Stable aggregates are resilient to rainfall and water movement. Aggregates that break down easily release individual soil particles that can seal the soil surface and clog pores.
The app is called SLAKES. It’s free. Depending on your device, you can downland SLAKES for Android handsets or SLAKES for iPhone.
Seeing how SLAKES works
The app works by measuring the size dispersal of a 2-15mm aggregate/ped when submerged in water compared to a reference image over time. As someone who has spent days measuring aggregate stability through weighing, drying, sieving, wetting, weighing, drying, sieving and so on, at Morley I was most interested to see how well the method works and the time it takes to carry out the process. For a less self-interested reason these more traditional methods are not particularly relatable to what’s achievable on farm. So, a simple, widely applicable method would not only allow us to test more plots or sites at Morley, but it would make our results more applicable on farm as growers can perform the same measure on their own soils.
Putting the new app to the test
When I got back to Morley, I tested the app on two sites across the farm where soil properties are measured as part of the Morley SAMS project. Using air dried soil for each site collected in 2021, I chose sites I knew had contrasting properties. P2 is a slightly heavier soil with higher soil organic matter as a result of it historically being permanent pasture, previous aggregate stability measurements through wet sieving identified higher percentage of water stable aggregates than H1 site.
You can see by the reference images that the 3 aggregates where of similar size at each site prior to being submerged (Figure 1). After 10 minutes P2 had only slightly increased in dispersal with little breakdown of any of the aggregates. The samples in H1 however had changed dramatically, two of the aggregates had completely broken down and the third partially broken down. The app allows the full results to be emailed to yourself as an excel file for further analysis.
The graph in figure one was calculated using the raw data and shows the slaking index proposed by (Flynn et al., 2009) which is calculated from the area of the aggregate at the start compared to the area after ten minutes. This provides a comparable measure to quantify the aggregate stability, H1 has a slaking index much higher than P2 in agreement with the water stable aggregate percentage calculated using the wet sieving method.
Table reports soil properties for the two SAMS sites in 2021.
| SAMS Site | Sand | Silt | Clay | OM | Water stable aggregates |
|---|---|---|---|---|---|
| % | % | % | % | % | |
| H1 | 72.0 | 15.5 | 12.5 | 2.3 | 40.7 |
| P2 | 62.4 | 16.2 | 21.4 | 3.7 | 66.5 |
My verdict on this new tool for soil testing
Although difficult to get the lighting right, and respecting the need for consistent uniform aggregates, the app looks like a most promising addition to applied agricultural research and farmers or advisors.
It is hope that we can find a MSc student this spring to apply SLAKES across the long-term trials programme at Morley to both identify what farming system practices might improve aggregate stability but also quantify how SLAKES is able to distinguish any differences between treatments, compared to more conventional wet sieving methods.
But before this, I encourage growers to try the app out on their own soils, potentially comparing areas where differences might be seen i.e., areas that have higher organic matter or even on area with high risk of soil erosion near gateways or on steep slopes.
If you would like help interpreting the results, I have an excel template that I can send via email so please do get in touch. Send me a message at David.Clarke@niab.com.
I look forward to hearing your results. In the meantime, I would like to acknowledge my CENTA Funded PhD at Cranfield University for support.