Saturday, 12 December 2015

Internal Consistency in Gardening

It is not consistent to attempt to dispel myths by producing more yourself. 

One of the most powerful concepts of science is internal consistency.  The laws of science operate in whichever science is being studied and consistency must be maintained within a science. 

So how does this apply to my gardening? 

Dowding suggests in his book "Gardening Myths" that digging is not necessary in a vegetable garden.  He is making the same assertion as Bill Mollison did in his book, "Permaculture: A Designers Manuel" written in 1988.  I'll go along with this.  I will avoid digging, however I reserve the right  to dig when I feel it is necessary. 

They both say that digging causes damage and death to soil inhabitants such as worms, beetles, bacteria and in particular mychorrhizal fungi and it also causes a loss of existing soil structure. 

Now to be internally consistent this should apply whenever digging is used. 

I have been turning over the compost in my compost bins today.  I try to turn the compost every two days as Geoff Lawton suggested in the Permaculture course I have just completed.  While the compost is being turned, I shake it out well with a fork.  After about ten days the constituents of the compost start to fall apart and turning becomes progressively easier. 

The compost is full of wildlife especially various types of worms.  However, there are also lots of beetles, slugs, snails, millipedes, centipedes and woodlice.  All of which are helping with the process of decomposition. 

As we have decomposition, there must be both bacteria and fungi mixed in with the compost.  Indeed fungi mycelium can be seen particularly in the woody material and tree leaves. 

So, if digging damages organisms in the soil, why  doesn't it damage them in the compost when it is turned over? 

Dowding says that there is a loss of organic matter from the soil as carbon dioxide if it is dug.  This is consistent with the reduction in volume of the compost as it rots down.  But, how is the carbon dioxide produced in the dug soil if there are no bacteria and fungi decomposing the organic matter? 

Bacteria and fungi use the carbon in organic matter to produce their mass and energy.  The final product of both these processes is carbon dioxide and water.  (For the scientists: catabolism when they are alive and anabolism when they die.)

Carbon dioxide is not produced by magic.  There is a biochemical process that can be described to explain its appearance and this involves the presence of bacteria and fungi. 

I would really suggest that bacteria and fungi are not killed off and digging does not sterilise the soil.  I wish it would because it would be an easy way of getting rid of club root and white rot fungi. 

So if club root and white rot are not killed in the soil by digging is mychorrhizal fungi?  I doubt it, but I still like to add mychorrhizal fungi spores when planting out fruit and vegetables.  The more spores there are near the roots the more likely they are going to be infected by mychorrhizal fungi. 

The same people that are telling me mychorrhizal fungi are killed due to digging then tell me it is not worth adding mychorrhizal spores because they are ubiquitous in the soil.  This is not consistent. 

There is some well documented data that suggests that there are less worms in cultivated soil than in  lawns and pastures.  However, beware of correlation.  Is the cause of this cultivation or are we just seeing a habitat preference?  Identifying cause and effect is not always that easy. 

There is no doubt that some worms are killed during digging.  The silly myth that one half of a worm will regenerate if it is sliced in two is false.  What you get is two dead halves.  There is also evidence that worms do not like disturbance so avoiding digging whenever possible is probably a good strategy if you want to encourage worms into your garden. 

Lets see if there is internal consistency with soil structure.

I would say that it takes about three to four weeks of turning every two days to make some good friable, well structured, open compost that looks very like good soil.  So if turning the compost does not destroy structure but, on the contrary, improves it greatly, why does digging destroy structure in soil?  I don't think it does.  It is the loss of organic matter that causes collapse of soil structure. 

There are many good reasons for not digging the soil but I don't think that killing soil organisms and destroying soil structure are two of them. 


  1. Surely digging breaks up the mycorrhizal networks which is not a good thing. But mycorrhiza can regenerate from all the spores that remain. No one is suggesting digging seriously reduces bacterial spores albeit no doubt a few are destroyed by exposure.
    I maintain my own opinion that mycorrhiza in a packet are of no value unless your growing media is sterile or has been sterilised.

    1. Just keeping all my options open Roger. Even I am susceptible to misconceptions. In my defence, I'm in good company. The RHS is still promoting mychorrhizal soil amendments.

  2. Dubious company in this case Anthony. I recently attended a lecture by a very well thought of expert in this field and you should have heard what he had to say - and that was a toned down version of what he privately said to my friend!