[dorsetmills]

We have just taken over an allotment that is relatively new - it was pasture a couple of years ago. We don't have time to dig it all before the growing season starts. We have dug two plots and the third was dug last year and is now very weedy. We thought about knocking the weeds down with a weed killer (Weedol) and planting potatoes through slits in black plastic sheeting. Do you think this will work?

[Trillium]

If you're spraying the whole area with the weed killer, then there's little point covering it with black plastic. A bit of overkill here.

When the sun hits the black later in the season, it will heat up the soil too much for potatoes which don't care for such heat. It will also limit the amount of rain the soil gets, if any.
Potatoes are better off being hilled up later in the season, which will also effectively kill off young weeds in the immediate area.

[Yorkie]

It may be too soon in the season to be using weedkiller, depending on the active ingredient in the particular weedol product you're planning on using.  Some of the products aren't suitable for use on land where you intend to grow crops, either.  Make sure you check this out before you start using the chemicals.

Others have reported some success in growing spuds through plastic.  One problem is that actual plastic is not water permeable and so it is possible that the spuds won't get enough water when they need it to swell the growing potatoes.

The other thing you should be aware of, is that former pasture land is commonly infected with wireworm, which loves potatoes.  If you're prepared for the fact that your spuds may have holes in (can cut them out on preparation) then you won't be so worried if it does happen for the first couple of years or so.  If you put plastic down, you prevent the birds from eating any spare wireworms which may make it to the surface.

[TheSpartacat]

We have just taken over an allotment that is relatively new - it was pasture a couple of years ago. We don't have time to dig it all before the growing season starts. We have dug two plots and the third was dug last year and is now very weedy. We thought about knocking the weeds down with a weed killer (Weedol) and planting potatoes through slits in black plastic sheeting. Do you think this will work?

Even if you used weedkiller, the soil will be full of weed seeds from years of being pasture land which will germinate over time- so you'll need to keep on top of them anyway with a hoe, so weedkiller won't solve that.
 
If you want to use plastic to stop them from germinating, giving you less hoeing to do, it will also serve to kill the weeds that have already sprouted.

Yes, you can grow spuds through plastic- i did it last year. When you're watering its a lot more fiddly as you have to take your hose to each hole and water each potato plant seperately, which is a big job if you're growing a lot of them.

On a plus point, they don't need watering as often as the plastic acts as a mulch, stopping evaporation.
On a negative point, even if the holes are small, because you're not earthing up, there'll be plenty of spuds that will turn green on you. (more than using the hill method)
Despite that, i got a good crop and it was a good way of using an area that i hadn't fully cleared.

There are other plants which also grow nicely through plastic and with fewer negatives like greening and long winded watering sessions- like squash and pumpkin?

[dorsetmills]

Thanks for the advice. Have got on with the digging/weeding and will give the plastic a miss this year. Lots of couch grass and a few wireworms  .