Welcome to the eighth instalment of our Know your Soils series sharing practical tips for monitoring the soil health on your land. Keep an eye out for our bitesize videos and fact sheets on simple tests you can do yourself on farm.
“If you can’t measure it, you can’t improve it.”
Try 3 easy soil tests to understand your soil health
After almost a year of supporting farmers with soil testing, the Soilmentor team share insights on empowering farmers to monitor and build soil health for themselves.
It’s clear that we need to build more resilient soils, both for the future of our farms and for the long-term health of the land. Satellite images of muddy waters spilling out of brown rivers after heavy rainfall are hair-raising. Soil health advisors are certain this scenario is avoidable, it’s all down to how land is managed.
If this is the case then building soil health should be one of the top priorities on every farm, but how do farmers do this? It starts with soil testing and monitoring, going out into the fields and seeing for yourself how your soil is doing.
Monitoring how your land is changing with different management practices and what works to build healthy soils and crops is the core of successful farming. This is why dedicating just one day to do a few simple soil tests on your land is the most important thing you can do for your soil this year.
Spring and Autumn are the best times to do soil tests.
Here’s the 3 most important AND EASY tests you can do now using equipment already on your farm.
1. Slake Test (Wet Aggregate Stability)
The Slake test allows you to really see how well your soil structure holds up in water. It is also an indicator of biological activity. Well structured soil is composed of aggregates, so in the slake test you put a few small pieces of soil in a sieve, submerge them in water and then shake them around quite vigorously. If the small pieces survive without breaking down at all they are true aggregates. The water around them will also remain totally clear. So after heavy rainfall, your soil would retain its structure and even keep little droplets of water in the nooks and crannies of the irregularly shaped aggregates. For non-aggregates there is considerable break down of the pieces and the water can become murky. This implies that the pieces of soil are only held together because of compaction, and as soon as there is a heavy rainfall the soil structure just falls apart and then what’s left re-settles and compacts further – no air gaps anywhere.
You score the breakdown on a scale of zero to eight, eight indicates a soil full of microbes and made up almost exclusively of aggregates. You can then easily record your observations and results using the Soilmentor app – including notes and photos all automatically assigned to the field you are in. Here is a step-by-step guide of how to the test and the simple equipment you need.
We are working with Soil Health Expert Jenni Dungait and have adopted the method she used in her research with farmers on multiple farms in Cornwall and Cotswolds regions. An additional benefit of this test was highlighted by Jenni’s research (soon to be published) which shows that the slake test is an excellent proxy for Soil Organic Carbon.
2. Earthworm count
All growers inherently understand the value of earthworms as we see them physically move nutrients around the soil profile. Earthworms are one of the larger organisms in the soil food web, so lots of earthworms is a good indicator of plenty of life in your soil. In the UK, an average of 15-20 worms in a 20x20cm soil pit is considered good. Taking a spade, digging a pit and counting earthworms is a very easy and valuable test and if you are using the app, it will automatically record which field the count was in and give you an average for each field at the end of the day. It’s also easy to look back and compare when you do the count again next year. Here is a step-by-step guide of how to do the test and the basic equipment you need.
There is a more detailed earthworm count you can do based on the work of soil scientist Jackie Stroud at Rothamsted. There are three main types of earthworm: the litter-feeders which break down organic matter on the surface of the soil; the top-soil worms who work on soil aggregation and nutrient mobilisation; and then the deep-burrowers that keep water flowing from the soil surface to deep pools below, as well as increasing aeration and root development. Jackie’s research shows that if you identify numbers of each type of worm, it can tell you what the worms are working on and uncover any changes you might need to make in your soil management to encourage all types – ideally you want to have all three types of worm working in harmony.
3. Infiltration rate
The Infiltration rate test clearly shows how ready your soil is to soak up water when it comes, and indicates the ability of your soil to hold water when it’s dry for long periods. Imagine if every farmer and grower around the land had a clear idea of the average infiltration rate in each of their fields. We would definitely be better equipped to prevent those muddy rivers and top-soil losses. To do this test we use a 150mm diameter pipe and hammer the pipe 75mm into the ground (We have pre-marked this on the side). Then we pour in 444ml of water and time how long it takes the water to infiltrate. If you use the app, it will automatically tell you the average infiltration rate for each field, each year, so you can easily compare between your fields as well as from year to year. Here is a step-by-step guide and list of the basic equipment you need to do this test.
Originally we used a much smaller diameter baked bean tin to do the infiltration tests but we were finding it took over 20 minutes for the water to infiltrate which made it impractical to do in the field. One thought was forcing such a small diameter cylinder into the ground was causing artificial compaction in itself, which is why we have moved to a larger diameter cylinder. We have found this size to be much more reasonable in terms of the amount of time it takes, our aim is that this method that takes a maximum of five minutes in most soils.
4. Bonus! Photo Diary
We are going to sneak in a 4th here because it’s not really a ‘test’. Farmers have told us that a photo diary of each field above and below ground is very helpful alongside the soil tests. You can see from the example on Fidelity’s farm below what this can look like in the Soilmentor app. And thankfully the app automatically adds a date and time to each photo and assigns it to the field you are in, plus you can add notes, so it’s all organised for you automatically when you get back home. No more scrolling through photos endlessly trying to find the right one or what exactly it was your were photographing!
The Soilmentor app makes it easy to record these observations in the field as you go, and then turn those observations into graphs and insights. Just a few taps and you have everything recorded, alongside photos showing what you saw both above and below ground. Essentially you can build up a visual diary for each field combined with numerical results from the tests. All those results are easily searchable (no more shuffling through piles of papers to try and find those scribbled notes) and quickly show how your soil health is changing over time. What do you reckon? Are you on board? What’s stopping you? If you have any questions at all just email us! We are here to help.
We believe that if we all take this on the UK can be world-leaders in healthy soils and clean waterways!
See our free online soils guide for soil tests you can do at home and find out how our app Soilmentor helps you record & learn how your soil is changing.