A visit to Charles Dowding's No-DIg garden and Kew Gardens

Introduction

Recently we have been learning more and more about the benefits of No dig gardening.

We have visited Charles Dowding’s garden in Somerset, the vegetable plots at Kew Gardens and had conversation with an organic farmer at the Alresford Show. We would like to share our findings with you. Firstly thoughts on Dig v No dig using trial results of Charles Dowding.

Dig v No dig

Two beds 5x16ft were started in 2013 and the harvested yields over the following six years are compared in the table below.

There were the same sowing and plantings into both beds. First sowing and plantings 12th March, then covered with fleece for 6 weeks. Growth was sometimes similar, sometimes very different.

	Dig	No dig
	Dug each December. 2in compost put under a spit of soil. 3-4 hrs extra needed for digging and then weeding the extra weeds in dug soil.	2in compost spread on top in December. No forking or disturbance except when harvesting potatoes (pulled out) and Parsnips (levered out with spade).
	Sow into surface soil	Sow into compost
Year	Kg saleable veg	Kg saleable veg
2013-14	186.68	188.25
2015	96.63	101.40
2016	99.37	109.43
2017	104.72	120.62
2018	79.70	104.10
Total	567.10	623.80

It looks as if there is not much difference in yields for the first two years but then the no dig bed outperforms the dug bed. Why is this? It may be because mycorrhiza develop in the No dig bed. It may be because when the soil is dug oxygen is added and the bacteria break down the organic carbon in the compost to carbon dioxide and the water holding capacity of the soil is lower.   

Comparing Dig and No dig and no rotation

Charles Dowding set up another trial comparing Dig and no dig, using different composts with no rotation year on year with surprising results

In this trial each strip of 2m x 9m was divided into 6 small beds where a wide variety of the same vegetables were planted each year.

Year		Minimal Dig Bought compost	No Dig Bought compost	No Dig Cow manure compost
		Soil loosened by forking each winter (no inversion) Then 2in bought compost (mix of green waste/ mushroom compost) on the surface each winter	2in bought compost (mix of green waste/mushroom compost) on the surface each winter.	2in composted cow manure on the surface each winter.
		Kg saleable veg	Kg saleable veg	Kg saleable veg
2014		67.92	78.55	74.51
2015		90.23	101.71	102.42
2016		120.33	142.14	111.97
2017		144.69	148.08	157.18
2018		105.27	115.37	112.03
[AR1] Totals		528.44	585.85	558.11

The vegetables grown were winter salads, beans, broad beans, Uchiki Kuri squash, spinach, land cress, cabbage, potatoes, leeks, lettuce, chicory and kale. Some beds were interplanted. Major weights came from Lettuce 16-20kg,  spinach 11-14 kg, broad beans  15-17 kg and potatoes 16 kg each year.

He commented that he had excellent beans and broad beans. But that the squash were not so good this year(2019). I observed from his more detailed results that there was no difference in the potato yields between the three strips this year. Maybe the lack of rotation is finally causing some nutrient deficiencies for some crops.  In other areas of his garden, Charles Dowding does not always follow a strict 4 year rotation as it is then easier to interplant and succession plant.

An overall conclusion from these two trials is that simple mulching with compost does improve yields of vegetables over digging or loosening soil by forking. Let the earthworms do the work!

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 [AR1]