This enterprising idea came from the Canadian Soil Association as a #soilmyundies challenge but is more than just a bit of fun. Biologically active soils grow better grass for beef and dairy herds because microbes and earthworms help to break down plant and animal matter which releases essential nutrients. Worms also bring nutrients up to the soil surface, where they are more available for grass growth. Their burrows create pores, improving aeration and drainage which makes for more fertile soil.

Soil structure can be destroyed by livestock out-wintering and excessive machinery movement, which close up the beneficial open-spaces. Ploughing also reduces the number of useful earthworms by breaking up their burrows.

The experiment highlighted this effect; a recently ploughed and seeded field revealed relatively intact underpants, indicating low activity and poor soil health. This contrasted with fields receiving a healthy dose of farmyard manure, which had excellent activity and produced heavily degraded pants.

Mike Harvey and his brother Christopher manage Middle Tregerest, a 120-hectare dairy farm in West Cornwall. They milk 150 Holstein-Friesians and also produce beef. The livestock relies on 80 hectares of grazing and silage pastures and Mike attributes their business success to a plentiful supply of good quality grass for grazing and silage. "A fertile and healthy soil is an essential part of our farm management. Looking at these pants I get the impression that there is plenty of action going on down below in our fields! In recent years we have been ably assisted by FACTs qualified adviser Jan from Cornwall Wildlife Trust who has carried out soil analysis for the farm. Recently she has provided much-needed help and advice on nutrient management planning and is helping us to comply with the new Nitrate Vulnerable Zone regulations for all of the Drift reservoir catchment area; a service which has been much appreciated by many farmers involved."

On a south-facing slope and benefitting from a combination of a balmy Cornish climate and well-drained, gritty black peat soil, Middle Tregerest Farm can grow grass year round. Mike and Christopher’s grass husbandry secrets include careful daily pasture rotation for their herd, as well as plenty of slurry storage to allow timely applications that maintain a high organic matter content in the soil. They also spot-treat problem weeds like docks, rather than boom-spraying, which keeps their grass-clover leys in good condition for much longer.

Mike is one of about thirty farms whose land drains into the Newlyn and Sancreed rivers, which end up in Drift reservoir. The reservoir is a drinking water resource which regularly suffers from algal blooms, fed by excessive nutrients coming down the rivers. Algae and its breakdown products must be removed from the water before it is safe to drink, which is a costly process. South West Water has partnered with Cornwall Wildlife Trust through the Upstream Thinking initiative, working with farmers to reduce soil and nutrients getting into rivers in the first place. The soiling-farmers’-undies initiative is one way to encourage improvements in soil structure and stability to safeguard Cornwall’s rivers and reservoirs. The project also part-funds farmyard infrastructure improvement like roofing, tracks, and fencing. Project ecologists carry out free farm wildlife surveys so farm plans can also maximise benefits for biodiversity. Farmers understand the need to manage the land sustainably to protect natural resources for future generations, so this kind of advice and practical support is well received.

As well as protecting the rivers – healthy and active soils also support a wider ecosystem. In particular, worms and insects in the soil are critical for the survival of farmland birds. The lapwing feeds exclusively on worms and insects and has sadly declined by 58% since 1970 in the UK. Soiling undies is one way of protecting Cornwall’s soil ecology to help reverse this decline.

Cornwall Wildlife Trust will continue to work with farmers and bury underpants to benefit soil, water, and wildlife. For more information visit http://cornwallwildlifetrust.org.uk/upstreamthinking.