Growing potatoes under black plastic

[svalli]

Last year I tried growing some potatoes under black plastic and since the trial was so successful I planted more that way this spring. In mid May I spread two pieces of 1 meter wide and 20 meters long plastic sheet on top of the tilled soil. I made two rows of slits in both plastic sheets and planted a potato in each slit.

This is how the potato plants looked in June.

[svalli]

Today was time to start harvesting them since most of the stems had started to die. It had rained couple of nights, but the soil was still quite dry and easy to dig. I was amazed about the size and amount of the tubers which had grown without watering them during them during the dry summer.

Sari

[svalli]

The first photo shows how close the tubers were planted to each other and how the potatoes were when the plastic was removed. This variety is King Edward, which I had only few seed potaoes.

Second photo shows harvest from four Mayan Gold seed tubers. Each of them had made about 12 potatoes. These had still quite much green on the leaves, but since the potatoes were already quite large, I ended up lifting also rest of them.

I have still three varieties growing under plack plastic and all the ones planted the traditional way in rows by the tractor pulled potato planter are still growing.

Sari

[brownrexx]

You got a nice harvest. I am surprised that they would grow in such dry conditions.

[nancyruhl]

Very impressive yields. Sounds like a successful and low maintainence experiment.

[Cole_Robbie]

Nice work. I am a fan of black plastic mulch, too.

[MI Farmer]

Wow - that's terrific, svalli. I'm curious, though, as to how deep you originally planted them? Also, did you add anything else at planting time?

[svalli]

Before planting I rototilled the soil and added granular fertilizer. The seed potatoes were just pushed beneath the soil through the slits, so they were not really deep.

I noticed that some varieties had grown many potatoes away from the stem and potatoes were either below the soil or just under the plastic and no green potatoes. The ones which have Solanum phureja crossed in them had the tubers close to the stem, so the potatoes on the top had got green in them. Those varieties may need some organic mulch or a bit of soil put on top of the opening in the plastic.

This was definitely so easy way to grow potatoes that we may skip doing it the traditional way. This takes more manual work during planting, but yield is much better. I can easily grow what we eat in three 1m x 20m beds. Once again we had to empty the root cellar from sprouted potatoes, which we grew for my father-in-law last year, so he may also now admit that there will be no famine even the cellar does not burst from potatoes at fall.

Sari

[bower]

Thanks for sharing this method. It seems almost inconceivable to me that potatoes can be grown without trenching/hilling them! Once or twice I planted potatoes and then failed to get them trenched when the time came, and yields were really poor. But perhaps that is because the trenching we do is a way of suppressing the weeds too. (We turn the weeds over with the spade so they also serve as a green manure, and usually put fish around the plants under the trenching.)


This method might work well at my friend's farm, where the soil is really rich (and of course applying some ferts at planting time as you do).



Is there anything you can tell me about the right plastic mulch? Is it durable enough to use for several seasons, or is one type better/more durable than another? I would like to look into the cost for that. Thanks!

[Nematode]

Very nice thanks for sharing.
I would eat the variety with green tops first, i think the drying of tops toughens the skin for storage.

[svalli]

The plastic, which I use is similar to the one used in the thick large trash bags. The one sold here is UV-protected and is sold for planting strawberries. I have used same plastic for many years for garlic and onions and with care at harvest time it can last multiple seasons.

I think that the potatoes do not really have to be grown in hills, if the soil is good and there is some kind of mulch to prevent weeds and sunburn on the growing tubers. We have grown potatoes many years, but it seems that there is still lot to learn about the methods and how the weather affects the size and quality of the harvest.

Usually we throw the green potatoes away at harvest time, but since the Phureja crosses are hard to find, I'm planning to save all green ones as seed potatoes.

Sari

[korney19]

Originally Posted by svalli

The plastic, which I use is similar to the one used in the thick large trash bags. The one sold here is UV-protected and is sold for planting strawberries. I have used same plastic for many years for garlic and onions and with care at harvest time it can last multiple seasons.

I think that the potatoes do not really have to be grown in hills, if the soil is good and there is some kind of mulch to prevent weeds and sunburn on the growing tubers. We have grown potatoes many years, but it seems that there is still lot to learn about the methods and how the weather affects the size and quality of the harvest.

Usually we throw the green potatoes away at harvest time, but since the Phureja crosses are hard to find, I'm planning to save all green ones as seed potatoes.

Sari

What low temps did you have when you planted them & throughout the season? I thought I read (or Tom told me) nights needed to be below 60F or something like that... I forgot the degree needed to form fruits...

[svalli]

Originally Posted by korney19

What low temps did you have when you planted them & throughout the season? I thought I read (or Tom told me) nights needed to be below 60F or something like that... I forgot the degree needed to form fruits...

Lows here when planting potatoes, can go below freezing, but hopefully not anymore after there is top growth. This year we had a frost even in July, which killed top leaves of some of my potato plants in the field, which is in a open area. Luckily my first planted patch was not affected.

If the lows have to be below 60°F, this area is the good for growing potatoes, since the average low does not get above that. Last summer there were some warmer nights, but also the colder ones too.

Sari

[brownrexx]

I do not grow mine in hills. I plant the seed potatoes shallowly in the soil and then cover with a deep layer of straw. I guess that I actually hill up the straw. You need to keep light excluded from the developing tubers.

This works well for a home gardener but wouldn't work so well in a farm application because you would need LOTS of straw.

DSC00880 by Brownrexx, on Flickr

Here is what the potatoes look like when I pull the straw back using just my hands. The 2 red ones must have come from a volunteer plant because my potatoes were planted in the same location as last year when I grew red ones. .

20180812_122732 by Brownrexx, on Flickr

[bower]

That's also a cool method, Brownrexx.
Tx for info about the mulch Svalli. I spent a few hours looking at different types last night - I'm amazed there are woven plastic fabrics that are rated to last up to 25 years. It would be so worth it, although you do have to burn the holes or else they unravel. I think this is what PH and PMcG are using for garlic.

I had some woven blue plastic tarps when I was first cutting wood here.. my goodness they didn't last more than a couple of years, and I literally spent.. days I guess if not weeks of my time trying to pick up the million little blue fibers that scattered everywhere. Something that lasts long is the best choice, but I will need some reassurance it can survive our freeze and thaw winters.



One thing mentioned about the woven stuff is that it allows air and water through. But you had success with a solid piece as well, and no drip irrigation - that's good to know.


Garlic and potatoes are two crops that rarely ever get watered even once during the season here.