In our on-farm variety trials, we generally ask that collaborating farmers use their usual seed-piece spacing for the trial, but to use the same spacing for all varieties. If you haven’t laid out a research trial before, you may be wondering how to ensure that tuber spacing is consistent between varieties. Consistent spacing allows for the fairest possible comparison between different varieties. Here are some spacing guidelines that you may find useful:

1. Between-row and within-row seed-piece spacing.

If planting into rows, most potato growers space their rows 30-36 inches apart. If you are planting into beds, you’ll want to plant 2 rows down the bed, with 2-3 feet between rows. You will be planting 10 seed-pieces per variety, as 2 side-by-side rows of 5 seed-pieces each. Within rows, tubers are generally planted 8-12 inches apart.

 

 

The table below shows the length of row needed for 5 seed-pieces. 

Desired within-row spacing of tubers	Row length for 5 tubers
8”	3 feet 4 inches
9”	3 feet 9 inches
10”	4 feet 2 inches
12”	5 feet

Length of row for 5 tubers (in feet) = (within-row spacing x 5) ÷ 12

2. Measure the total length of your planting area.

When you get to the end of the row (or bed) and find that there isn’t enough space for the last few seed tubers, it’s a frustrating experience – ask me how I know this! Take a couple of minutes to measure the area you have set aside for the trial, to ensure that it matches your plans. As an example, if you have 12 varieties to plant, and want to use 10 inch spacing, you will need 50 feet of bed, or 50 feet of paired rows. As the above table shows, each plot will be 4 feet 2 inches long (50 inches).

(12 varieties) x (5 seed-pieces per row) x (10 inch spacing) = 600 inches.

600 inches ÷ 12 inches = 50 feet.

3. Mark out the variety plots.

Stretch out a measuring tape and place a stake to mark the ends of the variety plots. In the example above, you would put a stake every 50 inches. If your plot is an odd length, you may find it easier to use a piece of twine cut to the correct length as your measure. I generally place a stake in only one of the rows, and estimate the end of the other by eye as I plant.

4. Plant!  

Once the plots are marked, it is easy to space the tubers evenly along each row by eye. This saves you from having to measure (for example) exactly 10 inches between each tuber in a row.

The small scale of the variety trial means that you will probably plant by hand. In a garden setting, this is fairly easy, and probably no change from your usual methods. If you plant mechanically on a field scale, you may find it easiest to leave the trial rows open, place the tubers by hand, and then mechanically close the rows.

Hopefully you’ll find these suggestions helpful. As always, if you have any questions about the trial, please feel free to contact me.

Ruth

This article was posted in Blog Posts.