To Dig or Not to Dig; That Is the Question

I have just taken over an extra half plot of land to augment my existing allotment; and my eldest son Andrew and I are in the process of preparing it for  cultivation next Spring [2017.] The reason behind this extra work is that I now have three homes to feed with fruit and vegetables. There is my own home, Andrew's young family and now Peter, son number two, is married and settled in Manchester. His wife is a vegetarian, so vegetables form a large part of their diet.So there is added demand on my gardening. I don't mind, for I have the time to garden, especially as I am winding up my tuition business and will have ended it by June. So more time for the allotment!

The plot was held by a young couple who had a young family, which they home educate. Lovely people, but they could not keep up the demands of a plot while rearing a family and the husband is working difficult hours. They have done a pretty good job of being rid of perennial weeds, but the ground surface show signs that it has been allowed to become overgrown with tussocky grass. So Andrew and I have begun the clearing process. Andrew took off much of the surface vegetation while I trimmed the bushes in the flower bed. Then we both set about digging, turning over the clods and extracting couch grass roots. This is  troublesome weed species that must be rooted out.  I am glad of the help of  a younger man, and we are going to get help from my two daughters-in-law in Spring, but they have already decided that they want to help with herbs and flowers. 

So without some digging no gardening can take place. Vegetables like a good, fine tilth, a soil turned into a fine crumb structure, and there they thrive. Furthermore, if you grow root crops such as potatoes you need to dig them out, and the same goes for carrots and parsnips. Furthermore, hoeing has a seriously important place in creating tilth, but hoeing disturbs only the surface and does not go as deep as digging does. In fact some digging can go down to two spades or more in depth,Sometimes you need to do this to eliminate pernicious weeds, such as Japanese knotweed.  

Trees and rhubarb, both involve occasional digging. Every five years or so you need to lift and divide your rhubarb crowns to ensure continued vigour. So you must dig them up and break them into two or more pieces. If you plant trees you need to dig a hole for them to go into. So gardeners cannot avoid digging sometimes.   

Charles Dowding is an expert gardener whose beautifully tilled plot lies in Dorset in South West England. For many years he has encouraged the no-dig theory of organic gardening, for he believes that digging lessens the soil's fertility. His plot has been no-dig for fourteen years.  Recently in Country Smallholding magazine [January 2017, which I received in December]  he published the results of a study in which he compared dug beds with undug beds. The study has been carried out over ten years, but in this magazine we got one year's results. For the sake of scientific accuracy he ensured that both beds were equally fertilized with compost, manure and rock dust. Charles does not use artificial fertilizers [ a view with which I personally agree] because they damage the soil fungi which do so much to enhance fertility. 

Taking the weight of vegetables produced during April to October 2016 the dug bed produced 98.86 kilograms of vegetables, while the un-dug bed produced 108.62 kilograms. But within these figures there is detail about specific vegetables.  Coriander produced exactly the same amounts, and shallots, peas [Delikett] , potato [Swift] and carrots were more productive in dug beds. But many other vegetables were more productive in the undug bed. Carrots sown between lettuce seemed more productive in the dug bed. But significant differences in favour of the undug beds were observed. These differences were in successional vegetables, these being beetroot after cabbage [dug 6.14kg to undug 6.85] kale after  beetroot [4.47 to 7.17] and dwarf bean Cupidon after cabbage [2.80-2.93. Both cabbage and kale are the same species, so maybe there are problems with the members of the Brassica family [to which they belong] in that the dug soil needs more time to recover from them than undug soil does. 

Charles notes other advantages to undug beds. They seem to retain water better than dug beds, probably due to their stronger soil structure. He believes that dug soil can produce a hard "pan" layer on the surface that slows down water absorption, yet it lets water drain away quicker when it gets in. He also notes that plants are better anchored against wind in undug soil.The dug plots seem more susceptible to weed growth later in the year than the undug plot does.  

He cites Professor Elaine Ingham who believes that digging and ploughing break up the networks of fungi in the soil that do so much for its fertility. Soil fungi, known as mycorrhizal fungi, dwell in symbiosis with plants, exchanging sugars, mineral salts and water with them to  their mutual benefit.  Digging and ploughing, she believes, also cause loss of carbon from the soil into  the atmosphere, contributing to global warming and soil loss, a kind of double trouble.

So what should we do about digging. To dig or not to dig is not the question, for we should be asking when and how much to dig. It is clear that Charles has a case, and he can make it on good scientific grounds. However, he must hoe the topsoil very well to produce beds with such a beautiful soil as he has. He admits to hoeing the soil and does not regard doing so as being in contravention to his no dig principles. But hoeing and digging are related activities, differing only in that one has a lighter impact than the other, for both break up the soil. 

It seems to me that there are gardening tasks that require digging, such as dividing your rhubarb crowns, which is a  process that is important for enhancing their vigour, but which involves digging them up. However, deep digging should be done but rarely and only for a specific purpose.  We do not need to dig every bed every year, for digging is not something to be done for its own sake. A simple hoeing of the soil and an overlay of compost might be sufficient in many cases. But a dug soil loses some of its cohesion, and so artificial fertilizers applied to it might be more easily washed  away than they would be in an undug bed. This suggests that the best materials for augmenting fertility in dug beds must be manure and compost, the latter of which holds nutrients in non-soluble form and so prevents them from being washed away.

We need to avoid excessively strict adherence to rules in gardening, and most rules may be better regarded as guidelines rather than rigid enactments that one cannot contravene.Certain pernicious weeds, such as couch grass, which tends to take over if left alone, have to be dug out. Moderation in all things!