No Dig Trial 2013-2019, current year at top
Photo above is 18th April 2019, dig bed left and no dig right. Same plantings, same compost.
This is similar to the trial I ran from 2007-2012 at Lower Farm. It’s to compare growth of the same vegetables in a dig bed and a no dig bed, all harvests recorded. At both Lower Farm and Homeacres, the area trialled was/is the same, 7.5sqm/80sqft for both dig and no dig.
12 year’s yields from 2007-2018 are 943.65kg (2080lb) from the dig beds, and 1027.61kg (2265lb) of same plantings from the no dig beds, at Lower Farm then Homeacres, six years in each garden.
Yields from the two Homeacres beds in the six years 2013-18 are
- 567.3kg (1250lb) dig bed
- 623.8kg (1375lb) no dig bed,
There are charts below, and analysis of the data by a statistician. This is the latest infographic, by Soul Farm UK:
For the seventh time, I dug the dig bed in December and incorporated two large barrows of compost, then simply spread the same on top of no dig.
The compost was 50% horse manure (6-10 months old, from the hotbed of last spring), 25% homemade and 25% mushroom compost/
On 1st April we pulled back the fleece to hoe the dig bed (many tiny weeds) and check progress. All plants sown and planted at the same time.
As last spring (see below), there are problems with the brassicas, beetroot and spinach of dig. Since spring 2018, the dig bed’s growth is weaker than it had been in earlier years, after I first dug the soil from pasture in December 2012. Yields 2013-17 were just a few % lower but last year was 24% lower, see below.
In the other trial we fork beds and apply compost on top. That reduces yields by less than this method.
By 12th June there is strong growth on both beds, except for dig’s spinach and beetroot. Most harvests are slightly higher on no dig, except for potatoes. Carrots are struggling on both beds and I am unsure why.
Through late summer and autumn, new plantings on the dig bed are stronger than in the spring. Notably the kale. However most harvests continue to be slightly heavier from the no dig bed.
Data analysis by Thibaut Olivier
Given the interest in the statistical analysis of the data generated from your dig/no dig trials, I used my scientific background to carried out some analyses and tried to extract as much conclusions as possible from the data you kindly provide us on your website.
For these analyses, I considered that: no soil bias and no plant outliers were present in the datasets. I also considered that for each year the same varieties were used and that the same surface was allocated for each vegetable type.
Indeed, in terms of methodology, as one of your Youtube followers already suggested, the fact that you apparently replicate your bed preparation types at the same place each year (no rotation) can indeed induce biases due to soil heterogeneity. Also, since the areas and numbers of plant individuals used are rather small in each statistical object, the data may be influence by outliers (data that differs significantly and abnormally from other observations in the same statistical object). We can indeed imagine that one of the plants in one statistical object does not thrive well (because of localised pest/disease or germination problem) and thus leads to an underestimation. Ideally, with such small plots, vegetable weights should be taken one plant at a time to allow detecting outliers and count the number of plants. It is of course a lot of work and not always possible. Another issue is the fact that not all year modality levels (2014, 2015, 2016…) refer to the same vegetable types and probably not to the same production surface for each type of vegetable (although I guess that most of the time it is the case). It is thus difficult to understand if the weights measured (in kg) can be considered as yield (kg/m²) and compared from one year to another for a given vegetable type. Also, variety names are not always mentioned in the datasets so it is sometimes difficult to figure out if the comparisons are possible (“carrot” vs “Carrot Nantes”; “Kale” vs “Kale Cavolo Nero” …).
On the other hand, I only analysed the “No Dig Trial 2013-2019” and the “three strip trial 2014-2019” datasets since I had the impression that, in the “lower farm” dataset, not all data were available on your website.
The datasets were analysed using linear models and the software “R” dedicated to statistical analyses.
In overall terms, no significant differences were found between “dig” and “no dig” levels in both analysed trials considering all vegetable types and all years (P>0.05).
Concerning the “No Dig Trial 2013-2019”:
Comparing “dig” and “no dig” levels, one vegetable type at a time, a significant difference was found for spinach (P=0.0338) and highly significant differences were found for kale (P=0.00726) and kaibroc (P=0.00123). In all these three latter significant differences, the “no dig” level showed greater weights.
Year comparisons showed that weights measured in 2017 was significantly different from those of years 2013 (P=0.0128) and 2018 (P=0.0275). But these results should be interpreted with caution (cf. remarks made here before).
Concerning the “Three Strip Trial 2014-2019”:
No significant differences were found between “dig compost”, “no dig compost” and “no dig manure” modalities (P>0.05) considering the whole dataset.
Comparing “dig – compost” and “no dig – compost” levels, one vegetable type at a time, significant differences were found for squashes (P=0.044) as well as “winter salads, spinach” (P=0.02), highly significant difference was found for parsnips (P=0.00938) and very highly significantly difference for lettuces (P=2.63e-05). In all these four differences, the “no dig” level showed greater weights.
Year comparisons showed that weights of 2014 was very highly significantly lower than those measured in years 2015, 2016, 2017 and 2018 (P<0.001). Weights of 2015 were significantly and very highly significantly different from those of 2018 (P=0.021) and 2017 (P<0.01) respectively. Weights of 2017 were very significantly and very highly significantly greater than those of 2018 (P=0.008) and 2016 (P<0.001) respectively. But these results should be interpreted with caution (cf. remarks made here before).
In overall, no significant differences of weights were found between “dig” and “no dig” levels in both analysed trials. Nevertheless, some vegetable types showed significant to very highly significant weight differences between these two levels. These significant differences were always due to greater weights in the “no dig” level. However, no similar vegetable type was found highlighted in both datasets (kale, parsnips, lettuce and spinach). Kaibrocs and squashes being only present in one trial, the significant difference found in their weights could not be further investigated.
December 2017 saw me on the dig bed’s sixth digging, with compost incorporated, and I spread the same amount of compost on top of the no dig bed. I used mostly horse manure from the greenhouse hotbed, which we had turned/moved out in May. This heap had been hot enough to kill the huge amount of grass and other weed seeds.
In early March there were weeds germinating on the dig bed and I hoed lightly, then again in late March. On the no dig bed there were hardly any weeds, thanks to the hot composting. Then on Easter Saturday 31st March, Steph helped to plant and cover both beds. Before that, in wet conditions where we could not hoe, she hand weeded both beds and found quite a difference in number of weeds, see photo.
The planting is, in order from the near end, onions 2 rows, kohlrabi, potato x 2 rows, cabbage, lettuce x 3 rows, carrot x 2 rows, beetroot, spinach, peas. Both beds are now all white, under 30gsm fleece.
Growth in spring 2018 showed more difference than ever before. The only things to grow better after digging were weeds and potatoes, perhaps onions though the harvest still awaits as I write this on 18th July.
Look at the differences between peas, spinach, beetroot, carrots, lettuce, cabbage and kohlrabi: all much stronger on no dig. Less pest damage on no dig as well – carrots were eaten by slugs on dig, and cabbage by wireworm.
During June and July we replant as soon as harvests are taken, so there will be a lot of second harvests in late summer and autumn. Already I picked the first cucumber, planted after potatoes. Biggest harvests so far are lettuce (9.42kg dig, 12.50kg no dig) and potatoes (15.79kg dig, 13.84kg no dig).
Total harvests to 18.7.18 are 27.97kg dig, 42.13kg no dig
By 6th October the dig bed appears, to some extent. to be repairing it’s soil. The June plantings of beetroot for example, are much stronger than the March ones.
However there are still bizarre anomalies. Celeriac on the dig bed looks good, but the celery next to it is measly and pale, half the size of celery on the no dig bed. Leeks and kale are smaller, carrots much shorter than on the no dig bed.
The drone photo below is mid September and the two-bed view is 12 days later. Harvests to 6.10 are 51.4kg/113lb dig, compared to 80.1kg/176lb no dig.
Looking ahead to the rest of autumn, there is still a lot to harvest!
Now it’s 20th November and most harvests are taken. The only one which saw more from the dig bed was celeriac, 4.23kg trimmed compared to 3.78kg trimmed from no dig. This is probably because the nearby peas were much more vigorous on no dig, and slowed the growth of newly planted celeriac in late May and June.
The leek harvest was 2.42kg dig bed and 3.82kg no dig, second crop after peas, seven modules of two leeks each.
Kaibroc broccoli is a third crop after potatoes then cucumber, up to mid November it gave 1.12kg dig and 1.31kg no dig, then we took a final harvest on 6th December. It would have continued to grow… but the dig bed needed digging! (which I did on 10th December). Incidentally, with no dig you can prepare ground for the coming year simply by mulching around existing winter vegetables if the spacing is wide enough, such as broccoli, leeks and kale: not salads!
Total yields for 2018 are 79.70kg dig and 104.13kg no dig. The largest difference in 12 years of doing this.
Preparing the two beds for 2017, in December 2016
See this video of spreading compost on the no dig bed, it’s a quick job. By comparison the digging of the other bed took longer!
On 13th March 2017, after some unusually mild weather with day maxima averaging 12C/54F, we sowed and planted both beds, with the same veg as last March, see below. The planting pattern is a mirror image of 2016, for a rotation of sorts, for example lettuce and potatoes swapped ends.
On 30th March, Steph and I removed the fleece covers, just for an hour, to check on growth. It was similar between both beds but a huge difference was the high number of weeds germinating on the dug bed, and very few on the no dig.
Growth through spring was steady, in temperatures mostly above average, with a last frost on 27th April of -2C/28F. Normally we have a frost mid May but not this year: May was almost the warmest ever, especially by night. See the results on this video.
There were strange differences with spinach, beetroot and onions struggling on the dug bed, while healthy on no dig. At the other end, peas and potatoes grew larger on the dug bed, harvests still to come. The images below are 1st June 2017, harvests to that date of 11.5kg dug, 15.1kg no dig:
By mid July, all first plantings are harvested, except for onions (soon) and parsnips. It’s a vintage year for onions here, with plenty of dry weather.
There were more potatoes and peas from the dug bed. Legumes generally yield a little more from tilled soil, while potatoes vary each year: in 2017 it was 11.07kg dug and 8.56kg no dig. Total harvests to 13th July are 37.65kg dug and 41.91kg no dig.
The beds were next planted with beetroot, French bean, kale, cucumber, radicchio and celery. Plus I sowed carrots between the lettuce, for October harvest.
By mid August the onions were dry enough to weigh, with 12.02kg/26.5lb on no dig and 11.9kg on dug, my best ever yield from that space of 11.5 sq.ft/1.08 sq.m. This adds to the spring onions we harvested from thinnings in late May.
The plantings we did on the day course of July 1st – chicory, celery and golden beetroot, small plants – grew fantastically in just six weeks and there were hearts of radicchio by 18th August.
Harvests of first plantings were 48kg dug and 54 kg no dig. Through August, we picked cucumber, French beans and beetroot, of the second plantings.
2017 harvests from both beds
|Lettuce, April to July||15.54||15.05|
|Cabbages, hearts in May||2.01||3.32|
|Spring onions May||0.34||1.31|
|Onion from own seed, July||11.90||12.02|
|Beetroot Boltardy, June||2.71||4.80|
|Spinach, May to June||0.46||3.25|
|Potato, first earlies, June||11.07||9.31|
|Summer sowings and plantings|
|Endive after onion, August, preceded Kaibroc||1.27||1.42|
|Kaibroc broccoli October-November||0.36||0.91|
|Carrots sown between lettuce, Sept-Oct||11.88||11.76|
|Endive, after shallot & onion, August to October||7.26||7.87|
|Cucumber after spinach, July-September, prolific!||12.42||22.25|
|Kale after beetroot, September to November||5.01||6.16|
|Cabbage after beetroot, October||2.51||2.15|
|Beetroot after cabbage, August||1.37||1.56|
|French bean after cabbage, July to September||1.86||2.22|
|Parsnips, October to November||7.44||6.14|
|Celery after potato, November||6.38||5.66|
Chicory after potatoes, August 18th
Beetroot Golden after cabbage, October
Chervil after onions, October-November
Mustards after cucumber, October-November
Chinese cabbage & fennel after chicory, November
|Totals 2017||104.72 dig||120.62 no dig|
Preparing the two beds for 2016, in December 2015
First sowings and plantings on March 14th, 2016 of carrot, parsnip (both sown direct) and spinach, onion, broad bean put in as plants
By March 21st, the beds are planted and sown, then fleeced over as its still cool with some frost and cold winds.
Now its wait and see what grows.
We finally removed the fleece covers on May 3rd and then growth took off in the new warmth, what a joy. By mid July, each bed has given just over 40kg of harvests with the dug bed slightly ahead thanks to higher harvests of lettuce, peas and potatoes, while no dig is ahead on carrots, cabbage and spinach.
Harvests and new plantings up to early August
Many summer harvests have finished, so there are now carrots growing where the lettuce were, endives after onion/shallot, kale and cabbage after beetroot, cucumber after spinach, French bean after cabbage and swede/kohlrabi after potatoes.
Harvest to August 4th are 51.0kg from the dug bed, 50.4kg from undug, of usable produce.
Autumn harvests were higher on no dig. It was a dry period and perhaps this reflects better moisture availability, from the higher numbers of mycorrhizal fungi.
Plus there was more canker on the dug bed’s parsnips, and more rotting of it’s swedes. Kale intrigued me too, the plants always looking more lush on no dig. During a gale in October, the kale on dug leaned over, those on no dig stood upright.
Table of 2016 harvests
|Lettuce, April to July||13.61||13.06|
|Coriander, dill interplant, April to May||0.30||0.30|
|Onion from own seed, July||2.57||3.35|
|Beetroot Boltardy, June||2.92||2.95|
|Spinach, May to June||4.08||4.34|
|Broad bean dwarf variety, July||2.87||3.27|
|Peas, June to July||5.29||4.78|
|Cabbages, hearts in June||4.84||5.06|
|Potato, first earlies, June||6.51||5.86|
|Summer sowings and plantings|
|Carrots sown between lettuce, Sept-Oct||13.46||12.94|
|Endive, after shallot & onion, August to October||7.26||7.87|
|Cucumber after carrot, got downy mildew (not powdery)||0.71||1.57|
|Kale after beetroot, September to November||5.03||7.89|
|Cabbage after beetroot, October||2.51||2.15|
|Beetroot after cabbage, November||6.14||6.85|
|French bean after cabbage, July to September||2.80||3.93|
|Parsnips, October to November||9.93||10.99|
|Swede and kohlrabi after potato, November||2.69||6.30|
|Mispoona, parsley after cucumber, October to November||0.95||0.97|
|TOTALS 2016||99.58 dug||109.57 no dig|
Preparing the two beds for 2015
Through March I plant and sow, the same vegetables as last year, in different places.
I removed fleece off both beds on April 12th. Growth is steady on both beds: broad beans look stronger on the dug bed while lettuce, spinach and radish are bigger on the undug bed. There have been many more weeds to hoe and pull on the dug bed!
I harvested some spinach and the radish in mid April, then we took a first pick of lettuce on April 21st, see the before and after photos, the yield was 880g of leaves from the dug bed and 1400g from the undug bed, whose leaves were noticeably firmer and larger.
In May the growth has been steady on both beds, nice weather. Cabbage look better on dug, potatoes look better on undug, as do spinach and lettuce, see photos below. Harvests to May 27th of spinach are 2.8kg dug, 3.1kg undug and of lettuce are 5.4kg dug, 7.1kg undug.
August update Both beds are now replanted with vegetables for summer, autumn and winter harvests, see table below. Already I have harvested some cucumbers (Tanya) which I planted after the lovely harvest of cabbage hearts in early June. We just laid mesh over the carrots, against root fly. French beans and the second planting of beetroot started cropping in mid August, photos are at that time.
December 3rd, final harvests are
|Harvests kg||Dig||No dig|
|Coriander, dill (9 plants) planted 25.3||0.56||0.58|
|Carrots Early Nantes sown 17.3||1.62||1.25|
|Cabbage Golden Acre (5) planted 25.3 (then cucumber planted 11.6)||6.23||6.61|
|Potato Swift (5) planted 22.3 (then French beans planted 22.6)||3.55||4.48|
|Beetroot (8×4) planted 22.3 (then fennel planted 19.7)||5.28||4.94|
|Spinach Butterflay (8) planted 17.3 (then swede planted 6.6)||4.04||4.43|
|Lettuce (mixed, 24 plants) planted 17.3 (intersown with carrots 6th June)||10.64||12.45|
|Broad bean (then Palla Rossa chicory planted 13.7)||8.71||8.03|
|Shallot (then beetroot planted 20.6, 8 plants x 3-4, multisown modules))||2.51||2.55|
|Onion (then Cavalo Nero kale planted 24.6, 5 plants each bed)||4.65||4.93|
|Cucumber, planted late June after cabbage||4.03||3.73|
|Dwarf beans, planted late June after potato||2.26||2.89|
|Beetroot planted late June after shallots||7.37||8.23|
|Radicchio (chicory) planted July after broad beans||2.24||2.99|
|Fennel Perfektion planted July after beetroot||0.79||1.82|
|Carrot sown 6th June between lettuce||8.00||10.44|
|Kale Black Cabbage interplant 24.6 between onions||7.42||7.82|
|Leaf radish after radicchio, planted 2.9||1.78||1.68|
|Again the pattern is of small, interesting differences, and broadly similar growth. Autumn carrots were amazingly different in favour of no dig, also with more slug damage to the dug carrots.|
Starting out in 2013
I made two large beds, five feet wide and sixteen feet long (1.5x5m), the same area as Lower Farm’s experiment, and used old oak planks from a tree at Lower Farm which I had had to cut down in 2003, as it was dying.
The planks are ten inches (25cm) wide so the beds are deeper than before, and more level thanks to the lack of slope at Homeacres.
These figures are after the FINAL HARVESTS on December 4th.
Excellent quality through October and November of celery, fennel, endive and beetroot, in the mild weather: look at the productivity of endive, from just 14 plants on each bed, planted after the magnificent onion harvest, picked every ten days of outer leaves, with harvests from 2nd September to 29th November.
I have not added the cucumber harvest to the main totals because it would distort the figures: there was a vole in the dug bed which ate the cucumber plant!
|Vegetable||Dug Beds kg||Undug Beds kg|
|Lettuce Leaves *||8.32||9.85|
|Beetroot (April planting)||2.58||3.02|
|Onion Red Baron||4.38||4.69|
|Beetroot (June planting) **||4.34||4.66|
|French Bean **||1.64||1.74|
|Endive Leaves **||5.65||4.69|
|Totals for season||81.82||83.24|
* 22 plants on each bed, picked every week from May 13th to July 23rd
** 2nd planting
*** I have not added the cucumber harvest to the main totals because it would distort the figures: there was a vole in the dug bed which ate the cucumber plant!
The experiment in 2014
Before and after digging and composting, December ’13.
Bed on left dug with 3 barrows homemade compost in the trenches. The same amount of compost has been spread on right-hand, undug bed. In this case the compost is lighter colour than the soil on left, which also has some of last year’s cow manure on the surface, brought up in digging. Soil is more crumbly that at Lower Farm, loam over the clay below.
How I dug the ‘dug bed’, wheelbarrow top right has soil from the first trench, to go in the last trench. Photo on right is a first sowing on December 8th of Aquadulce broad beans, which were then dibbed in. A foot to their right I intend planting another row of Aquadulce which I soed in modules in November, in the greenhouse.
In early March I spread a three quarter bucket of SEER rockdust on one side of each bed, to see what differences it makes
Also in early March, with fine weather bringing plants on fast, I filled the beds with onion, shallot, beetroot, cabbage, lettuce and spinach plants, also I sowed carrot, parsnip and planted potato Swift. So by March 9th the beds are full, and fleeced over.
Module raised plants from the greenhouse, not hardened off as they are covered immediately with fleece, they include lettuce, cabbage, beetroot and onion (small, on right), and the right hand photo is both beds planted and ready to fleece over on March 9th.
Sowings and plantings 2014 with spacings between rows
8cm Garlic own bulbs, cloves planted 26.10, harvest 20 June
11cm Onion Sturon (7) v small sown 19.2
12cm Onion Red Baron Moles (8) again v small, sown 19.2
12cm Shallot Zebrune POD (5) sown 14.1 and 3 own Red Sun from 2013, harvest early July
10cm 8.3 Carrot E Nantes Milan + radish Cherry Bell – eaten by slugs, replaced by celeriac Prinz 28.5
13cm Beetroot Boltardy (7) SH sown 14.1 – harvested late May to late June
14cm Cabbage Greyhound (5) sown 14.1 – harvested early June to mid June
15cm Lettuce 4 Maravilla, 4 Relay
9cm Lettuce Red Cos POD (8)
9cm Lettuce 4 Eibacher Fels SH, 4 Mottistone – all lettuce harvested weekly, late April to
15cm 8.3 Parsnip Gladiator POD + radish Cherry Bell
14cm 8.3 Potato Swift 5 plants per bed – harvested late May to early June
15cm Spinach (8) Mississippi Moles, 1 or 2/module – harvested mid May to late June
15cm B Bean Aquadulce plants sown November- harvested late May to mid June
12cm Same but sown direct on 8.12, own seed, 13/row
Image below is mid July, garlic harvested and followed with golden beetroot, new celeriac, cabbage followed by French bean, broad beans at far end followed by swede and kale, hidden behind the parsnips which are on the large side. Dug bed on left, undug on right.
By the end of July, many changes have happened again. Golden beetroot are well established where the garlic was. Onions are now drying in the greenhouse and I have planted beetroot and endive where they were. Lettuce are almost finished and the French beans have grown enormous in no time; they were planted after the cabbage harvest.
These figures are after the final harvests on December 4th. First harvests were in May.
|Vegetable||Dug Beds kg||Undug Beds kg|
|Lettuce Leaves *||9.31||10.38|
|Beetroot (April Planting)||2.95||2.92|
|Onion Red Baron||3.79||3.84|
|Boldor (June Planted) **||8.43||8.33|
|Endive Leaves **||2.78||3.05|
|Kale, small leaves for salad **||0.76||0.82|
|Parsnip (One 5ft row!)||12.47||14.40|
|Beetroot (July Planted) **||2.68||1.7|
|FINAL TOTALS to December 2014||104.86||104.92|
* 22 plants on each bed, picked every week from May to July
** 2nd planting
As of mid-September, both beds look full and productive but the dug bed’s crops now look slightly stronger
As of mid-October, crops look quite similar and gaps are now appearing adter the leek and carrot harvests.
By early November, the only harvests to make are red beetroot, celeriac, swede and salad kale.
By 4th December, the last kale is harvested and its time to to dig the dug bed, back to top for 2015.