Farmers aren’t scientists.
They work long, hard hours outside in all conditions – it’s tough, manual labour.
They don’t have white coats and laboratory equipment.
So, analysing the fertility of their soil can be a slow and costly process to undertake.
But knowing the fertility of their fields is crucial.
Because that’s where everything either grows or it doesn’t.
That’s what’s really creative about the Canadian Soil Association’s initiative.
They showed farmers how to test their soil for fertility, quickly and cheaply.
All they need is a pair of dirty cotton underpants.
When they’ve worn them for a while, they bury them in a field and wait two months.
After two months, they dig them up.
If they’re full of holes and disintegrating, it means the soil is healthy and organically thriving, great for crops.
But if they’re still in the same state they were when they buried them, it means the soil is poor quality and not good for crops.
Organically thriving soil needs to be full of microbes, bacteria, fungi, protozoa, nematodes, anthropoids and earthworms.
These will make short work of a pair of cotton underpants.
If the underpants aren’t eaten away, it means the soil has none of this activity.
Therefore, it doesn’t have sufficient nutrients for healthy plant life.
Farmers in California and Canada began spreading the word about this simple test.
They called it #soilmyundies.
It became amazingly popular and it spread to the UK, Australia and New Zealand.
Famers can plant dozens of pairs of underpants all over their farms, in different areas of different fields.
They need to know whether the soil is too dry, too wet, too acidic, too alkaline, over-worked, lacking nutrients or low in other organic matter.
Then they can work out how to treat their soil in order to improve it.
Evan Wiig, executive director of the California Farmers’ Guild, said: "Cotton is an organic material and breaks down naturally just like anything else you’d put on your compost pile.
"So, if you bury cotton in soil teeming with life, all those creatures will begin to feast on it.
"If you have dead soil, if it is totally lifeless, you should be able to pull the underpants out of the ground, throw them in the washing machine and put them on like nothing happened.
"But if you have healthy soil, you should have nothing left but an elastic waistband."
Fertile soil isn’t just crucial for crop farmers.
Cattle farmers or sheep farmers need lots of lush healthy grass for their grazing herds.
That’s why #soilmyundies caught on with farmers all over the world.
Hard-working people who need a fast, simple answer they can do something about.
And word has spread throughout the international press as well as the farming press.
The learning for us is what made it catch on, how did it go viral?
The truth is, the test will work just as well with anything that’s 100% cotton.
Whether it’s a T-shirt, a tea towel, a pair of socks or just any piece of cloth.
It doesn’t have to be underpants.
But calling it a name like #cottonsoilchallenge just wouldn’t have caught on.
It doesn’t sound silly and naughty, it doesn’t sound fun, like #soilmyundies.
The test would work with anything cotton, but it wouldn’t get as much press.
It wouldn’t make people laugh, so it wouldn’t go viral.
As Walt Disney said: "We have to entertain in order to educate, because the other way round doesn’t work."
Dave Trott is the author of Creative Mischief, Predatory Thinking and One Plus One Equals Three.