We completed the installation of our irrigation system back in November but we did not need it active over the winter as our stock is minimal at this time of year. Now we are starting to pot-on seedlings and plug plants into the trays we sell in and the volume is about to expand very rapidly so this week I have been working out how to operate the water. Our irrigation comprises:
* a big tank that holds rainwater that is captured on the roof of the polytunnel
* a small feeder tank underground where the water is pumped from and any surplus drains back to
* a fairly powerful pump
* 34 flood trays where the plants live and are watered from below when the trays flood
* a controller which luckily comes with a booklet that is written in standard English rather than techie jargon
The latter and I have been getting acquainted and after a lot of button pushing and head scratching I have managed to get the system set to come on at 9am on Mondays and Fridays and pump water into the trays. The tricky bit is working out how many minutes it needs to pump water for and then how long the water takes to drain back out of the trays. It turns out that we can fill 17 trays (it fills half at a time) in just 6 minutes but was then taking over an hour to drain out. The plants seem to be able to take up enough water in about 45 minutes so I resorted the very high-tech solution of drilling bigger drainage holes to speed up that stage.
Now I need to check it again and keep adjusting till the balance is right. I also checked that all the trays are completely level, which is really only possible when they have water in them to show any high or low points. The trays sit on rails made out of scaffolding poles that in turn are supported on simple U-shaped brackets with a screw fitting that enables them to be adjusted up and down by turning them.
Its all a bit time consuming but when its done it will save hours every day of watering and the plants will be much healthier watered from below as it avoids compaction of the compost. Overall, I am quite pleased with myself for managing to work it all out.