Friday, June 12, 2015

Mulching experiment with yacon and oca

I have just finished digging the last of the oca and some of the yacon. After reading this little article on mulching potatoes:   I decided to do a bit of experimenting with mulching myself.

Last spring I planted six beds each of oca and yacon - two each with a thick straw mulch, two each with no straw just like usual, and two each with no mulch and no summer shade.

When I first tried growing oca many years ago I mulched it and all the tubers rotted. At the time I did note to myself that the mulch and the soil was too wet which is what contributed to the rotting but it did put me off mulching and I have  advised people against it since. I have to admit now that I was wrong and I should have tried it again.

Here are the results of my experiment.
Mulched bed - The tubers took weeks longer than the bare bed to shoot which is not a problem in my long growing season but I did worry that the tubers had rotted and did overplant one of the mulched beds with melons, which actually did surprisingly well growing in among the oca when they did get going.
The plants took a long time to catch up to the height of the bare bed plants but the eventual harvest was around the same.
Usual unmulched beds with summer shade: The harvest was a bit down on last year but still ok. I usually use shadecloth for my yacon until they grow too large for the covers.
Unmulched beds with no summer shade: These plants stayed very small and sickly, around 60 or so cm tall. They all survived but the harvest was abysmal and there were very few eating size tubers.

Conclusion: Yacon need shade when small here in summer but mulch is unnecessary.

Mulched bed: The tubers took weeks longer than the bare beds to shoot which is not a problem, later shooting even seems to help with plant health. The tubers came up in dribs and drabs which made me think that some tubers had rotted but eventually they all grew.

The plants were bigger and healthier with very little stem rot problems. They took a couple of weeks longer than those in the bare beds to die down after the frost weather started which seemed to give them more time to grow their tubers. The harvest was much better than the bare beds and with a much bigger proportion of eating size tubers (over 5cm). The tubers were also cleaner and easier to harvest. Most plants gave just under 1kg of tubers.
I was worried about mouse and slug damage but there was little evidence of either though I think in another year with more mice they might prefer to live in a mulched bed.

Usual unmulched beds with shadecloth covers: Harvest was down this year with a large proportion of small tubers. Usual amount of stem rot. Shadecloth was left on all summer and until the first frosts in late autumn.

Bare beds with no shade: As I expected nearly every plant died during the heat of summer, only two plants survived with no shade and that was only because a nearby plant gave them a little afternoon shade. They produced only a handful of tiny tubers.

Conclusion: Clean mulch really makes a huge difference in oca plant health and harvest size. I am still a bit worried about pest problems but I think the mulch is still worth it. Next spring I will experiment to see whether straw or geocloth makes a better mulch.

Just an extra note: I also hilled up another bed of oca when they started showing a lot of stem rot in the hope that it would help the plants put out new roots from the good parts of the stems. It worked well and when the weather cooled down in autumn (the heat seems to cause the stem rot) they had a new lease on life and started to grow vigorously and produce tubers.

1 comment:

  1. Thank you for sharing your experience with the mulch. I used cut grass with some of mine this year. They were the only ones to survive. When temps went to 97f I lost most of my Oca. I feel so much better now after reading your post.