We already have our beloved solar tunnel that moved with us from Scotland to here and doubled in size in the process. However, we eat such a lot of tomatoes that this polytunnel is no longer big enough. Plus we've also had enormous success this year with cucumbers so we want to build on that too. Plus we want to grow melons in the summer and more winter salads so we decided to build another.
This one is a more 'traditional' polytunnel though we have put in a very UNtraditional watering system that we hope will ease the number of labour hours required to water it. The solar tunnel has a seep-hose installed just under soil level. Although that reduces the time spent watering, it requires mains-pressure water to go through the hose so we're unable to utilise the water in our rain-water harvesting system unless we use watering cans, a very labour intensive process.
The new system for Polly 2 was inspired by a fascinating article by Steve James in Permaculture magazine (no. 66 Winter 2010) that used an Incan technique to self water a greenhouse. Basically, water is harvested from the roof of the tunnel or greenhouse into a lined gulley under the growing space. This seeps in between small stones beneath raised beds and waters the plants from below. The soil on the top remains dry so it is no longer a slug haven and it also counteracts the nasty problem of moulds. The tank/gulley has a wooden slatted walkway above that forms the pathway through the tunnel.
Even if we don't get masses of rain, we can still divert the water butts into this tank if needs be. So the tank has been dug out, lined, the stones put in (plus some branches in a hugelculture mindset), and the earth put back in. We've planted in some broad beans to increase the fertility of the soil for next spring. Here is the work in progress, aided by our lovely WWOOFers (and children!).