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To dig or not to dig?

By 30th August 2021No Comments

That is the question! Until very recently, I was firmly in the digging camp. Well-schooled in the art of turning over the soil to a full spade depth at the end of the growing season, I was convinced of the merits of digging to bury the annual weeds, to incorporate compost or well-rotted manure and to expose the compacted earth to the winter frost. My approach was supported by none other than Adam the Gardener whose pearls of wisdom were aired in a weekly cartoon strip in the Sunday Express (sometime in the last century!). He identified the purpose of the exercise as ‘to get the topsoil exposed to the severe weather so that many of the harmful insects and weed seeds are killed’. The only drawback to digging that Adam acknowledged was the hard labour it involved. This was undoubtedly true in my parents’ garden where heavy clay soil required the use of a fork rather than a spade, but here in Tayport, on Ogilvy Street, we have light sandy soil which makes digging to a full spade depth much easier. So, if digging offers all these benefits and is not particularly hard work in our garden, why decide to try ‘no dig’ cultivation?

The answer to this question is quite complicated but has its roots (please pardon the pun) in efforts to improve the soil. Although light sandy soil has many advantages for a gardener (free drainage, easy cultivation etc), it also presents significant problems. Free draining sandy soils are vulnerable to drought and are often nutrient poor. To make matters worse, periods of extended wet weather can leach nutrients out of the topsoil into the ground water, further reducing the fertility. To address this, I tried to improve the soil with regular (and frequent) additions of organic matter in the form of compost and well-rotted manure. A treatise on composting is beyond the scope of this blog but, suffice it to say, I compost everything I can and enrich the heaps with manure generously donated by our three chickens. My home-made product is occasionally supplemented by a trailer load of Discovery compost from the Riverside depot in Dundee. However, my efforts to improve the soil have had only limited success. Vegetable crops are reasonably good, but I am not achieving any obvious long-term improvement in soil structure, so moisture and nutrient retention is still poor. What am I doing wrong?

To answer this question, I started to read about the fundamentals of good soil structure and soon realised that there was more to it than just digging in compost. Soil structure is dependent on the presence of an incredibly diverse microbial population, both bacterial and fungal, which is essential to break down the organic matter (in the compost) and release the nutrients that the plants require. Soil dwelling invertebrates (particularly earthworms) also play an important role in the incorporation and degradation of organic matter by encouraging the growth of a beneficial microbial community, and by secreting compounds that bind soil particles together to create a crumb structure. So how can we encourage the development of this community of beneficial soil-dwelling microbes and invertebrates?

This is a question that has nurtured a growing school of ‘No dig’ enthusiasts exemplified by a market gardener called Charles Dowding. At face value, I find the arguments for ‘no dig’ very persuasive, but coming from a scientific background, I have decided to run my own no dig experiment which I will present in this blog as soon as I have more evidence. In the meantime, you might wish to check out Charles Dowding’s website at https://charlesdowding.co.uk/ and see what you think.

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