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
|
|
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!
