Using tech to talk to soils

As technology advances, so do soil assessment approaches. Ellie Dearlove reflects on some options that promise to add value to tried-and-tested techniques.

In simpler times, your senses, a spade and how machinery worked the land were the main ways to assess soils.

Yet, recent advances in technology are generating an ever-expanding list of options to measure numerous aspects of soil health.

Such advances often promise to deliver virtually instantaneous results (you’ll see the term ‘real-time’ a lot) and even provide predictions to inform crop management.

With the general condition of arable land declining (e.g. see this UK government report (2023) and Rothamsted Research paper (2020)), we need as much help as we can get.

But it is important not to let cool tech distract us from getting the fundamentals right.

One readily adopted innovation has been mounted or handheld soil scanners.

These generate field-level data on soil texture, moisture and organic matter, via two approaches:

• Electrical conductivity (EC) scanners (require soil contact)
• Electromagnetic induction (EMI) scanners (held above the soil)

The scanners, which provide comparable information on soil variability, work best on bare soils in discrete zones (areas with similar soil properties).

However, their readings need careful interpretation to account for variation in soil properties, especially texture. For example, clay and sandy soils give very different signatures.

The University of Plymouth is trialling a novel approach that detects natural radioactivity signals from soil minerals to estimate soil organic matter and moisture levels.

The sensors have been mounted on a robotic platform to deliver faster and potentially more accurate data than traditional field-walking approaches.

Other above-ground sensing technologies include those that provide eyes in the skies, allowing measurements to be conducted from greater distances and scales.

Soil brightness maps are a good example, where satellites measure how intensively bare soil surfaces reflect sunlight, which can be used to indicate soil moisture, organic matter content and texture.

But such maps have limitations. For example, it’s not possible to compare results with those taken on different dates or locations.

The UK Soil Observatory (UKSO) also provides an interesting and free-to-use resource. It combines satellite information with national survey results and long-term monitoring data in one interactive map.

Various soil probes can provide information on moisture, temperature and nutrient levels, with data either captured by in-field loggers or, increasingly, beamed straight off to a remote device.

Apps are also being developed to visualise the readings and highlight the trends.

Probes can help target nutrient applications and even model crop development and predict yield weeks, maybe months, in advance.

There are already interesting portable soil testing devices already on the market.

For example, one can measure volatile organic compounds (VOCs) produced by microbial activity and claims to provide in-field data on about a dozen soil health indicators (including soil organic matter, various nutrients and pH).

Although trained on mineral arable soils, the company recommends it’s used in conjunction with traditional analysis methods.

As a technology to watch, we are testing it in our Strategic Cereal Farm network, alongside other innovations, such as Paul-Tech probes, which can provide information on nitrogen uptake.

Elsewhere, ecoacoustic technologies are being developed that listen to invertebrate activity by analysing sound signatures with a Soil Acoustic Meter (SAM).

In-field DNA metabarcoding kits may also be able to reliably profile soil invertebrates and fungi.

Another exciting initiative is the cosmic-ray soil moisture monitoring network, which was set up in 2013 (COSMOS-UK).

Run by the UK Centre for Ecology & Hydrology (UKCEH) and funded by the Natural Environment Research Council (NERC), the 47-site UK network is based on fascinating science.

Put simply, cosmic-rays naturally generate neutron particles that interact with soil water molecules. Sensors can measure this interaction and estimate soil water content.

Each sensor is extremely sensitive and can indicate soil moisture over about 12 hectares. It has the potential to transform the way that we understand and model the natural environment.

Soil health is complex. As the options to measure it increase, it’s important not to lose sight of the basics.

Used on a rotational basis, our soil health scorecard is a practical and tried-and-tested way to make sense of soil testing results. It can also be used to help ground-truth some sensor data.