news

Too clean?

November 12, 2015 Harley Farmer

It’s amazing how those old phrases are so often proven correct, isn’t it? The “hygiene hypothesis” is one of science’s attempts to explain why a bit of dirt is a good thing. But is all dirt equal? And does timing have a lot to do with the outcome? No, all dirt is not equal and yes, timing is very important. Both are really relevant aspects of this much debated topic and there is only time to skim over the issues here.

Olivia strawberries 151010

Dirt is dirt to the uninitiated. This photo shows Olivia from next door helping transplant strawberry plants in my back garden. For several years she’s been a keen beneficiary of our strawberry crop yet a bit young to take part in production. This year I offered her the chance to have a row of her own, as long as she helped with the ‘work’ of planting her row. I was correct in predicting her enthusiastic acceptance yet I was quite surprised with her willingness to get a “little bit” dirty. Olivia is quite the tidy lady who normally leaves “mud” to her little brother Henry — more of that in another post. But this time she was in there really taking part. Apparently the prospect of her own strawberries took precedence over getting dirty.

What’s the point of this story? The dirt in my organic vegetable patch contains high levels of compost and therefore huge numbers of bacteria and other microbes.  That soil is heaving with wildlife yet it’s perfectly safe because it’s in balance. The strawberry plants grow strong and productive and people getting dirty are safe, especially when they eat the strawberries.  No artificial chemicals are involved as I feed the soil, the soil feeds the plants and the plants feed us.

How does timing relate to that?  What if this had been happening 200 years ago? It’s likely horse manure would have been in the compost and also spread raw over the soil. That would have meant a lot of anthrax spores in the soil and even a few on the tasty strawberries. Had the gardening process caused a break in the skin those spores could have penetrated resulting in a very painful toxic death from anthrax. Or it might have boosted the gardener’s immunity. A bit of a lottery in which those still alive at harvest time would have enjoyed the strawberries.

Now we vaccinate against anthrax and the medical challenge is to have people boost their post-vaccine immunity with tiny regular amounts of exposure. There will almost certainly be anthrax spores in the soil shown above yet Olivia and I are safe and can expect to be alive when the crop is ready; partly because of our vaccinations and partly because we regularly boost our immunity with exposure to ‘dirt’ and all that goes with it.

Now Olivia has a lesson in patience — 6 months to wait for her mouth-watering sweet strawberries!

Dr Harley Farmer PhD BVSc(hons) BVBiol(path) MRCVS

Organic gardener, developer of young minds, apparently a ‘fun’ neighbour.



Older Post