[JCloth]

Hello

I have just created a bed on a slope which is 90cm deep one end and 30cm at the other.

I was thinking of putting an irrigastion pipe under the soil because I would imagine that the soil would get drier than in non-raised beds.

If this is correct and a good idea, how deep would I put the pipe? About 30cms?

Or am I better watering the surface?

Thanks.

[Trillium]

Raised beds do get drier than non-raised, but not that much drier if you've added lots or organic matter to the soil first.

I'd suggest you put the pipe about 5cm below the soil and if it's a slow system, then allow about 8 hrs/week of run so that the water slowly seeps down to the bottom roots. This is a superior way to water all plants, and being a bit under the soil you protect the pipe from any  degeneration by UV rays and evaporation. It's easily moved as you fluff up the beds next year.
It its a fast run system, then try to slow it down so the soil can absorb it.

[JCloth]

Excellent, thanks for that advice.

[Trillium]

I neglected to mention that the 8 hour run of water should be all at one time - this gives the most benefit rather than lots of shallow waterings which causes more plant stress than benefit.