Can you really grow potatoes under mulch with no digging at all? And if so, how would the yield and labour requirement compare to methods that did require digging? That is exactly what I set out to learn in a controlled trial this season. We grew potatoes using three different methods on the same plot so we could compare the results. The video below shows you the full growing process from bed preparation to harvest, and at the end, I take some time to walk you through the results to help you decide whether you would like to grow potatoes with or without digging.
The Three Growing Methods
The three methods compared in this trial are No Dig, Double Dig, and No Till. I demonstrate each technique in the video, but here is a quick overview:
The No Dig technique avoids all forms of digging by simply placing the seed potatoes on the surface of the soil and covering them with a thick layer of mulch for the remainder of the growing season.
The Double Dig technique requires extensive turning and digging of the bed space, after which the potatoes are planted below the surface of the soil.
The No Till technique uses a broadfork or garden fork to loosen but not invert the soil first and then the seed potatoes are again buried a few inches below the surface of the soil.
In order to achieve a fair comparison between these three techniques, we needed to control all other variables to the best of our ability. First there are the obvious factors like irrigation, sun exposure and temperature, but our control couldn't stop there. In past Q & A sessions, we have covered how we know that the depth of a seed potato can influence yields, along with hilling. The size of the seed potatoes has also been shown to influence the overall yield. Therefore, it was critical that every one of these variables was controlled while we changed the primary growing method in each bed.
Our Trial Process
Now, here's a video showing the full growing process from spring to fall. I wanted to be thorough and clear about how the variables were controlled and show everything that happened throughout the season. As a result, there is a lot here, so feel free to jump around to different parts of the video to find the subjects you are most interested in. There are timestamps below.
Video Chapters: Background 1:28 / Bed Preparation 6:10 / Planting 11:14 / Maintenance 17:08 / Harvest 22:02 / Results 25:48
As I anticipated, one of the biggest differences between these three growing methods was the amount of labour required. I did not know what to expect from the final yields, but I did expect the No Dig method to be the least work, and that it was. The No Dig bed required only 32 minutes of work from start the finish, followed by the No Till bed at 44 minutes, and the Double Dig bed at 69 minutes. As you can see from the clip below, I am simply picking up the potatoes from the No Dig bed without any digging at all! That was a treat!
Conclusion
After watching this video of the process, I hope you have more of an appreciation for the level of control that is required to perform a fair comparison. Any one of these beds grown by itself would have provided us with very little information because we would lack any form of side-by-side comparison. I think I controlled things sufficiently well here, and I am especially thankful that I decided to run the trial with two different potato varieties in each bed. Had I chosen just one variety for the entire trial, my conclusion could have been quite misleading. For example, if I had just grown Norland potatoes and found almost identical yields in each bed, I might have concluded that the growing technique has a negligible impact on yield. Alternatively, if I had just grown Smart potatoes, I would have dismissed the No Dig technique for the much lower yield it offered with this variety. Thankfully though, we ran the trial with the two varieties and gathered evidence to support the following conclusions:
It is possible for No Dig potato growing to rival the performance of digging methods with significantly less labour.
The performance of a potato with each growing method will depend on the variety.
Since our two potato varieties performed so differently in this trial, I can't help but wonder what might happen if we continue to put other varieties through the same trial. I would also be curious to see how repeatable these results are on plots with different soil types, so perhaps this is only the first of many potato trials we will conduct! For now, I will rest satisfied in what was learned from this first effort and start collecting ideas for what to try next. I will post all of the result tables from this trial in the Classroom as well so we can continue the conversation there.
