I came across a large sheet of thick black polythene - about 2m x 5m and thought it would be good to warm the soil before planting. Is this a good idea, and what crop would benefit from it? I'm not about to start planting just yet, but thought I would plan ahead,
Definitely a good idea but I would wait until the frost has had a chance to break down the soil and kill off a few bugs (the unwanted ones!) then get it down before the weeds make a start and it will help in two ways.
The plants that are planted early in the season will obviously benefit most and if we have a wet spell it will keep the ground drier (assuming it is polythene sheet and not groundcover material that lets the water through.
I use black polythene to warm the soil from the beginning of Feb for about 3 weeks prior to planting early potatoes. Works a treat, I then put fleece on for another 6+ weeks and earth up until the frosts finish.....works for me here in Derbyshire! ;D I also tried planting squash through a large sheet last year and it was a disaster, so won't be doing that again! ::)
Like Deb, I immediately thought of potatoes but take care that the slugs don't take up residence under it for the winter. I planted pumpkins through it last year with great success. As it isn't porous it will keep moisture in but also prevent rain getting through so I would suggest you keep an eye on soil moisture levels.