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.
