A new way to quantify soil health allows farmers to measure any improvement over time, as well as identify potential issues that could hold back yields.
Until now, there was no simple tool allowing farmers to compare their soils and follow their evolution over time.
“Farmers knew they needed to improve soil health, but they didn’t know how to measure or track it,” says Liz Stockdale, head of farming systems research at Niab Tag.
So, to help farmers assess soil health, the Soil Biology and Soil Health Partnership – funded by the AHDB and the British Beet Research Organization and led by Dr Stockdale – has spent the past five years combining key aspects physical, chemical and biological in a simple dashboard. .
One of the first tasks was to examine what could be measured and how convenient it was to measure it.
A wide range of indicators (physical, chemical and biological) were assessed by the research team and narrowed down to a handful that are important for understanding soil health.
The result is the Soil Health Scorecard, which uses a simple traffic light system to assess key indicators of soil health based on benchmarks.
What does the Soil Health Scorecard include?
The scorecard uses seven different metrics that researchers have found essential to define the health of a soil.
- Soil organic matter
- Vess (visual assessment of soil structure)
- Earthworm numbers
For each of these factors, there are benchmarks that determine whether the result is green, orange, or red.
Green means typical or optimal result, amber means examination and red means further investigation is needed, with action taken if necessary.
For some measures like organic matter, the baseline numbers will vary depending on the soil type (light, medium or heavy) and the region of the UK.
Therefore, a red number means that the OM is below average for that soil type and region. These benchmarks should be published in the coming weeks.
How to use it
Assessing soil health is markedly different from assessing soil for nutrient planning or tillage, so it needs to be dealt with separately, says Dr Stockdale.
One of the challenges of any soil test is getting a representative sample so that any change between years is due to soil changes rather than location.
She says it’s now easier thanks to geolocation technology using a phone – for example with the what3words app.
This means that when you come back to do assessments in three to five years, you’re back at a similar location within 4 meters – so roughly the same location, making it repeatable. What changes, then, is the soil itself.
A good place to start is to look at the yield maps and think about where you want to locate the sample points. “You want it to be representative and not random,” she says. These may be areas that are performing well or poorly, and this will help explain why.
You will need to keep the geolocation data safe, for example backed up to the cloud in case you break your cell phone.
For these assessments, she uses a bucket with a trowel, a worm identification card, and a Visual Soil Structure Assessment (Vess) scoring sheet. She places the bucket in the chosen location and will then sample in a 5m circle around the bucket.
2. Field assessment
For the Vess assessment, farmers have to dig three pits with a spade. They can use a typical 8-inch shovel or a smaller shovel, but numbers like the number of worms will need to be converted to standard volume.
Use the spade to cut three sides, then lay the block on the ground. Next, inspect the soil on the side that was not cut by the spade, as smudging can confuse things.
Vess assessment involves feeling how easily the soil breaks down. For example, is there compaction and is there something limiting crop growth?
Dr Stockdale also advises taking a photo of the second or third pit as a reference for the next time.
In addition, the scorecard requires the count of earthworms for each pit. She advises to carefully check the rooting area for worms.
“About 30-40% of the worms are in the rooting zone on arable land, or even higher with cover crops, so you have to find them. “
It takes about 15-20 minutes to do all three blocks, but it will be longer in the grasslands as there are more roots to tease the worms.
3. Soil analysis in the laboratory
For soil analysis, she advises taking 10 to 15 samples from the site with a trowel, mixing them in a bag and sending them for analysis.
Organic matter, pH, P, K and mg levels are required for the scorecard.
It is also great for farmers to get a measurement of microbial activity at the same time, as benchmarks will eventually be included in the dashboard.
The soil should be moist, but not wet, to make the Vess assessment, and should be warm for worm activity.
The ideal time is when the soils get wet in the fall, which can be around the beginning of November, depending on the weather.
This can also be done in the spring, but it is more difficult to find the right time because the soil dries out quite quickly, which makes the window shorter. This is why fall is preferable.
However, Dr Stockdale cautions that farmers cannot compare the results of fall and spring worms because they will be different.
She recognizes that neither is the right time, with everyone coming up against key growing or planting times. “But if you let the winter pass, you will get zero results,” she warns.
“It may be a rainy day when you can’t drill, but it’s okay to do the soil assessments. “
How did he behave?
The soil health scorecard approach is tested in trials and it has successfully shown changes in soil health during manure application and plowing.
To test the approach, a network of seven experimental sites was set up. One trial at Loddington focused on tillage, another at Adas Boxworth focused on drainage, and a long-term trial at SRUC focused on pH.
One of the researchers involved, Adas soil specialist Anne Bhogal, says she is a fan of the scorecard.
“The approach found differences, showing that you don’t need to do anything out of the ordinary to get an indication of the effect on soil health.”
In Loddington, the field was not plowed for seven years, and researchers plowed a few strips to see the impact. Plowing has considerably reduced the number of vulpines.
The scoreboard showed a drop in the number of worms. But after three years, the numbers had recovered, says Dr Bhogal.
Vess’ score increased after plowing as he attacked a compacted 15cm layer.
At Harper Adams, the approach was used in a trial of adding organic matter.
One observation was that there was more greenery where compost and manure had been applied, showing that light textured soils responded well to the application of organic matter.
This approach also showed that soil health declined over the four years of arable farming, with a decrease in the number of organic matter and earthworms.
The Soil Health Scorecard is expected to launch later this year. For more information, visit the Large soils page of the AHDB