Farming the past and the future

Henry Webber – one of our PHD students at the University of Bristol – discusses the surprising intersection between archaeology and precision farming.

Agriculture and archaeology may not seem related fields, but my research project – at the universities of Bristol and Reading, alongside Historic England– has shown how a common fascination with the soil could both benefit farmers and rewrite the history books.

As a farmer’s son, I’m familiar with farm management, and the latest developments in agricultural technology. But where most farmers might use a drone, or a satellite, to record and manage variation of their crops to reduce inputs, increase yield and enhance environmental sustainability, I’ve been using the power of precision farming to gain insights into Roman villas and Stone Age monuments.

Currently around 60% of the UK’s farmland is under some form of ‘precision farming’ management and the UK government’s recent paper promised to grow markets for “innovative farming technologies such as drones” – as part of a post-Brexit move towards “efficiency driven agriculture”. The question is how could this help the study of archaeology, and how can current knowledge of archaeological sites help inform future agricultural advice?

The clues are in the crops; changing soil properties caused by ancient man-made features affect the health of the plants above, revealing the buried features below at the right time of year. For the first time, I’ve been using a type of multi-spectral sensor attached to a drone to map archaeological features from Neolithic henges, to Iron Age enclosures and Roman villas, while also testing whether this archaeological information could be useful for a farmers agronomic management.

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Archaeological features buried under ground can affect plants that grow above them. Plants that grow on soil above the remains of a foundation for a wall (left) will generally not fare as well as plants that are above the remains of an old ditch that has been filled in (right). Image courtesy of Micasense.

Moving away from drones towards the dirty end of the tech scale, I completed detailed soil sampling and geochemical analysis using an X-Ray analyser called a portable XRF, to find out whether these archaeological sites affect the nutrients in the soil. This has shown a doubling of topsoil phosphorous over areas of archaeological remains.

Phosphorus is one of the major nutrients needed for crop growth and it’s applied by farmers every year to keep their crops healthy. This phosphorus most likely came from concentrations of people or animals living in the same area for hundreds of years. Other elements like zinc (see Figure 2) are also closely related to archaeological remains for reasons that are still unknown.

This sort of information might be useful to farmers because many archaeologists and archaeological companies survey large areas of land with geophysics or drones to narrow down possible locations to dig. Once gathered, this data could be useful for a farmer explain soil and crop variations. For example, if it can be shown that a patch within a field has an archaeological site in it, the soil might have double the amount of phosphorus in it, meaning the farmer can apply less there, saving money, and ensuring soil phosphorus levels are not excessive.

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 From archaeological geophysics (left) and detailed soil sampling showing zinc variation (centre) can help explain crop marks seen by farmers in precision farming data (right).

Of course this data sharing can work the other way. Archaeologists might welcome data gathered by farmers to help learn more about the extents and details of an archaeological site. Multi-spectral drone imagery has already led to new archaeological features discovered on the other sites I have looked at.

What this research has proved is how important sharing knowledge and data are. Farmers sometimes have mixed feelings about archaeologists and vice versa, but using these comparative datasets I’ve been able to explain to farmers and archaeologists how to add value to farm businesses and data to the archaeological record.

To achieve this, I’ve been keen to engage with industry, opening up access to the latest agricultural equipment and developing a rapport with farmers; alongside taking part in an RCUK policy internship at the Royal Society to understand the wider policy angle to this research for future agriculture and heritage conservation.

For more detail see a recently published article in the Journal of Archaeological and Anthropological Sciences.

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