The No-Dig Garden was one of the four family scale gardens that I established when I first started
this RED Gardens Project all those years ago. It has been the garden that I had the highest
hopes for and probably been most disappointed by, until recently.
This No-Dig Garden is now doing quite well, producing lots of high quality vegetables,
but it took more time to become really established that I had thought, for a few reasons.
I think the potential benefits of a No-Dig approach like this can be really interesting,
and could lead to better crops and bigger harvests,
and I wonder why it hasn’t started to produce significantly better than the other gardens yet.
I first established this No-Dig Garden using the lasagne method of covering the undisturbed ground
with undecomposed organic matter, a method I had learned about through the permaculture movement.
But I didn’t really do it very well, mainly because of a lack of resources and time, and I
didn’t really know what I was doing back then. I continued with that method for quite a few
years, and noticed that there were a few key issues that made the method less successful
in this temperate maritime climate. The layer of decomposing organic
material became an excellent breeding ground for slugs, one of our main pests,
and the covering kept the soil underneath cool, which seemed to delay the growth in the spring.
Five years ago I decided to switch to a No-Dig method that I had learned about
from Charles Dowding, which was apparently much more appropriate for a cooler climate,
and involved mulching with compost, or organic material that had already been decomposed.
Because the area of the garden had already been established, with the vegetation removed,
I decided to use less compost than is usually recommended to start with.
Looking back I think it would have been better to have started with a
lot more compost, if I had been able to get it.
I only had a limited amount of my own compost available for this garden, and for the first
year I supplemented it with horse manure and bedding that we hauled in from a local farm.
Together this added up to almost 3 cubic meters of compost, which spread over the
4 large beds of this 100 square meter garden, produced a layer of compost only
3 centimetres deep, or just over one inch. This is significantly less than what is
usually recommended for the first year of establishing a garden like this.
But it is close to what is recommended as an annual top up layer of compost,
so I thought that this would be fine, as this space was already established.
The garden grew reasonably well for that first year after switching to a new method,
but not necessarily better than it had in the past or in comparison to the other gardens.
The following year I decided to finally start buying in municipal compost,
as I wasn’t able to make enough compost myself, and I needed an easier option to
get a lot more compost for the increasing amount of growing spaces in this project.
That year I spread over 4 cubic meters or about 44 wheelbarrow loads of this
clean and easy to manage compost onto the large beds of this garden,
producing a layer of 5 centimetres or 2 inches deep.
And for each of the next three years I added an additional 2 to 3m3 of the
same municipal compost, adding another over the old layers of compost on the same beds.
So I have brought in a total of about 15 cubic meters of compost in five years for
this one garden, with the 12 large bags that I bought in the past 4 years costing €900,
which is a fairly big investment, especially compared to some of the other gardens.
So, over the last 5 years we have added layers of compost that add up to about 17.5cm or 7 inches,
but of course the level of the top of the beds in this garden
are only marginally above the surrounding soil.
There was some compaction of course, but all the compost that we have added has further decomposed,
reducing in volume, and a lot of the carbon within the material would have
been consumed by soil organisms, and released into the atmosphere as CO2 gas.
Some of the nitrogen that was in the original compost would have been lost to the air through
common biological processes, and some of it probably leached into the groundwater.
Hopefully a lot of the nitrogen stayed in the soil, along with a lot of the other nutrients,
which is what the plants are looking for, and a fair amount of carbon is still there,
which has significantly darkened the topsoil. When I dig test holes in the soil of this garden
there is a gradual transition from darker to lighter, which is what happens in a lot
of natural ecosystems, but is not really visible in the soil that I regularly dig.
I recently took soil samples for testing from all of the gardens, before adding any of the compost
or fertility for this growing season, and after drying the samples, the soil in the No-Dig Garden
is noticeably darker than the other gardens. This is because there is a lot more carbon
or organic matter in the top layers of the soil of this garden, which is what I would
have expected with all the compost that we have added, and that we have never dug it.
This is essentially the remains of the compost that has been added over the years,
some of it near the surface seems to be still decomposing, and the worms
and other soil organisms have brought a lot of it deeper into the soil, and transformed
it into a diversity of soil organic matter. It is fascinating to see this happening over
just a few years, and it is definitely a sign that the topsoil is improving in this garden,
possibly becoming better than the soil in the other gardens.
This should increase the nutrient and water holding capacity of the soil, and provide a
lot more food for a wide diversity of soil biology, which remains largely undisturbed.
All of which should help make more of nutrients available to the plants,
either from the compost that we added or from the soil itself, and in theory this should help make
this garden more resilient and productive, though I’m, not sure I am seeing that yet.
I think the municipal compost we have been using is part of the issue, as it still has
a fair amount of decomposing to do when we add it to the surface of the garden beds.
And because it was made with a lot of woody material there is still quite a
high carbon to nitrogen ratio, with a lot of the nitrogen essentially locked up or
unavailable to the plants, at least until there is further decomposition.
I confirmed this with the potato grow bag trials last year, where the plants growing
in this type of compost didn’t produce well unless regularly fed with something high in
soluble nitrogen while they were growing. And the compost didn’t seem to be releasing
enough nutrients for the potato plants until later in the season,
possibly because of the warmth of the summer speeding up the decomposition process.
I realise now that a relatively thin layer of compost sitting on the surface of the soil is
not going to be decomposing very quickly, but a new layer will be covering the remains of the
compost from the year before, and what remains of the even older compost underneath that.
I suspect that a lot of the nutrients taken up by the plants last year was
brought into the garden in the compost that we added several years before that,
which had finally decomposed enough to release a lot of the nitrogen and nutrients it contained.
I wonder what would have happened if I had bought in enough compost to cover all of the
beds to the recommended depth of 10-15 cm in the first season of switching to this method.
At the time I was really hesitant to buy in the 10 or 12 large bags that
I would have needed to do this, but I now think it would have sped up this process.
A thicker layer of compost would have provided a greater volume
for the plants to forage in for the nutrients that they need.
And as the sun and wind can dry out the top part of the compost, with a deeper layer, more of the
material would remain moist and protected from the elements enough to continue active decomposition.
The other option that has been recommended by other growers would be to use a layer
of much better quality compost on top of the soil, with a thicker
layer of lower quality compost in top of that. This makes sense to me, as the higher quality
compost would be better able to release enough nutrients to feed the plants for the first year.
The better compost would also potentially bring in a lot more useful biology, which could speed
up the whole process of decomposing within the poor quality compost that was covering it.
With this method, the lower level will be feeding the plants that year and boosting the biology,
the middle layer will be continuing to decompose for feeding the plants in the future, and the top
layer will act as a mulch to protect it all, which will be covered in the following year.
Because I didn’t start with such a thick layer, and have only been adding lower quality compost,
the potential benefit to the plants and the development of the garden,
probably took an extra few years.
When buying this compost I knew that it was not very rich, and added some
chicken manure pellets as a concentrated fertility, thinking it would help a bit,
and have added some more over the years, though not very consistently.
Looking back I now realise that it probably wasn’t enough to make any significant difference.
Between all of the amendments and liquid feeding, I calculated that I added a total of about 800g of
nitrogen over the past 4 years, which translates to a total of about 10g/m2 of nitrogen added to
the growing beds of this garden over 4 years. I now think that 10g/m2 each season would
been better to supplement the poor quality compost, and as some of the nitrogen would
have been absorbed and locked up in the compost itself, perhaps even more would have been useful.
Essentially I bought in a lot of carbon that didn’t contain enough nitrogen.
So I could have bought in additional nitrogen to amend it, and to feed the plants until things get
established, or waited until the material decomposed or matured enough to a much
more useful carbon to nitrogen ratio. The other option of course is to get
better quality compost, but clean farmyard manure can be difficult to get around here.
And in this context it is probably easier and cheaper to buy in a supply of concentrated
nitrogen than it would be to buy in and spread even more of the lower quality compost.
I am quite pleased with the crops that we have been able to get out of this
garden over the past few years, but is is still not as good as I would have thought,
at least compared to the other gardens. This is a difficult thing to really compare,
as the gardens aren’t set up for direct comparisons, which would
require eliminating a lot of the other variables. But it is possible to compare some crops growing
in three or four of the other gardens, even if plant spacing and other factors are different.
A crop of curly kale in the No-Dig Garden did about as well as it did in the other gardens,
comparing both the yield per area and per plant, and the plants all looked
equally healthy across the different gardens. The squash plants produced a lot when measured
per square meter, but not a lot from each plant, but the plants in the No-Dig Garden seemed to
die back earlier in the season than in some of the other gardens, which I though was strange.
The courgette plants in the No-Dig Garden produced a lot more than in the other gardens,
and these plants seemed to have what they needed to grow really big, and to produce a lot of fruit.
The early potato crop wasn’t great in comparison to the other gardens, though it was nice to easily
pull out the buried potatoes by hand from plants that were earthed up with even more compost.
The runner beans were similar to the rest, and any difference in the yield per square
meter or per plant is likely due to differences in plant density.
And this was probably also the case with the different crops of peas, especially as the peas
and beans can use the help of special bacteria to produce extra nitrogen in their root systems.
The carrot crop in the No-Dig garden was probably the best out of all the gardens,
with a bigger crop of roots that were not forked. But this difference was probably more because this
was the only garden that we had successfully prevented the carrot root fly from getting into
the crop, but it was nice to see that they could grow well in the uncultivated soil.
So, overall the No-Dig garden did about as well as the other gardens,
at least in terms of what I was able to observe and compare,
and most of the plants looked quite healthy across all the different gardens.
Any difference is probably better explained by some other factor,
including mistakes that I made as a grower, but I guess I was expecting that the soil in the
No-Dig Garden would produce something noticeably better, and I haven’t been able to see that yet.
This No-Dig method is definitely less work in some ways, especially when not needing to dig the soil,
and less time spent weeding, and both of these can be really beneficial in a busy season.
So it can definitely be worth starting a garden with a No-Dig method like this,
if you can get, and can afford the amount of compost that’s needed.
And I think it might be better to invested in more compost earlier when starting this garden, and
better quality compost or any amendments, rather than adding smaller quantities over the years.
But I don’t really know that yet, and it will be interesting to see how
successful this approach is in the No-Till trials that we set up a few months ago.
But there are supposed to be other benefits of not disturbing the soil, at least compared to the soil
of the other gardens that are regularly dug over. The soil profile looks great and it looks like
there is significantly more organic matter in this topsoil, and a lot of worms and other soil life,
which hasn’t been disturbed through cultivation. All this should help lead to increased and more
diverse soil biology, as well as better nutrient and water holding capacity in the topsoil,
and all of this should help to grow healthier and more resilient plants,
which should be able to produce more. Perhaps some crops are doing better,
but this could be due to other factors, and the plants in this garden do not seem to be
consistently better than the same plants growing in gardens that are regularly dug.
There are some other variables involved, and I am planning to regularise the planting
plans between a few of these gardens this year for better comparisons.
We are also adding supplies of nitrogen, as well as some seaweed meal below the layer of
compost this year, as I think this will help. And it will be interesting to see the nutrient
profile when the soil tests come back from the lab, as there could be other imbalances
or deficiencies that could be fixed. Perhaps this No-Dig benefit might be
delayed for some other reason, or it’s possible I am just expecting too much from this garden,
but if not digging the soil can be potentially beneficial in so many different ways,
I would have thought I would have seen more of a difference between the gardens by now.