The usual term is "consistent soil moisture levels", not "consistent watering". Very different things. ;)

It means keep the soil the roots are growing in slightly moist all the time rather than dry/wet/dry/wet etc. That way they have a consistent source of water. But it doesn't mean soaked or drenched, just damp. And it isn't just lettuce but most all garden vegetables.

The easiest way is to use a drip irrigation system set on an auto timer so that several times a day the plants receive a small amount of slowly delivered water.

Dave

Great explanation, Dave. So often the difference between success and dismal failure in a garden is the result of good or bad watering techniques. I love soaker hoses and I'm in the market for a good timer. Any suggestions? (Yes, I'm going to ask on the irrigation forum, too.)

I use drip irrigation from Dripworks, including a digital Orbit timer I bought from them. It's held up well and is very easy to program for up to 4 waterings on whatever days of the week you choose.

I don't think that soil should always be kept moist. I like to let the top few inches of soil dry out between deep, thorough waterings, to prevent rot and encourage plants to put out wide, deep roots. Lettuce may have special requirements.

Got it !! Thank you so much for your explanation Dave ;)

Now days the drip technology has evolved a lot and I used drip tapes for my row crops

https://www.dripworks.com/drip-irrigation/irrigation-kits/drip-tape-row-crop