Here's another option.

I've been told, and hope to experiment this year, that arrangements like the ones on the left work fairly well, and are supposed to work even better if there is a second supply line on the far end. The advice that I got last year, coupled with my own unsuccessful experiments (best advice, lay this stuff out and pin it down before your plants are big). Long stretches of curvy soaker tubing, even if it is connected at both ends, will tend to deliver water unevenly.

Okay, that's exactly what I was concerned about. I'll go with the bottom left option on the first picture. Should I put the soakers under or above the mulch?

I would go with the first option. Here is why:

The longer any individual length of hose is, the more uneven the pressure will be at the far end. I have run 50' lengths of soakers arranged like your second drawing and it worked fine for a couple months, but hard water deposits started clogging the micropores which increased pressure on the remaining pores and the beds nearest the main supply sprung leaks in the far end of the hoses. These were repairable with duct tape (what isn't repairable with duct tape ;-), but the frequency of leaks increased with time.

By the end of the season the soakers closest to the water supply were in horrible shape. I was using a timer so it was possible for the water to be horribly uneven for awhile before I would notice.

The advantage of your first drawing is less pressure variance and if a hose does become defective you don't have to replace the entire soaker, just that one section.

Will one soaker line per square suffice or should I go with two lines per square?

The spacing of soakers is somewhat dependent upon what you are growing and what the growing media is made of.

If you need the soakers to keep seeds moist then you need tighter spacing with loose soils like Mel's mix and can go with further spacing for tight soils like topsoil. This is because the smaller the particle size of the media, the more capillary action will wick the water horizontally as it sinks down in the soil.

Using Mel's mix with soakers I get about a 2.5" band of wetting on the surface, but then it fans out horizontally as I inspect lower in the soil column.

With Mel's mix if you need the soakers to keep a seed bed moist at the surface for something like radish or carrot or anything with 3" spacing or less then you don't want more than 6" spacing between soakers.

If you can handle manual watering until germination then you can space further apart because just a few inches down all will be moist with 12" spacing.

For your first year I would suggest 9" spacing as a good compromise and see how it goes. You can always adjust as needed next year.

Alternately you can go with one soaker per square if all plants in that 'row' are 12" spaced plants. Just plant the seed right next to the soaker. Go closer for plants grown closer.

Thanks a lot, timewind and justaguy! Starting in the AM!

Do you have to use soaker hose? What about the 1/2" poly hose where you punch holes for the little 1/4" tubing with the different drip heads? Already bought supplies and am drawing up the plan tomorrow morning.

Aulani, that is what is being used here. Instead of using drippers you can use 1/4" soaker hose that attaches to the 1/2". There are different kinds of 1/4 soaker, one that is just punched with holes and the other that's more like a tradition permeable soaker hose.

I'm so glad to have found this thread. I asked a similar question without the nifty diagrams that are very helpful.

Yes, I'm glad to have found this thread too, and great diagrams! I saw that 1/4" soaker hose yesterday in the store. This helps a lot. I think I'm pretty well set now. I laid most of the 1/2" line day before yesterday, but it rained a little yesterday and it's too cool today and no sun. Good for transplanting, but not laying irrigation. That stuff is unwieldy without the sun. Must be patient!!! Thanks for the comeback.

Okay, now I have another question. I made a mistake with layout and needed to change to a T-joint. For the life of me, I couldn't get the hose out of the T-joint so I just had to cut it off. I was working here in the house this morning, trying to get the piece of hose out of the T-joint and am even using a pair of pliars to no avail. Am I missing a secret? I'm about to throw it away. The stuff stretches, doesn't it?

on barbed fittings, sometimes it will come out, sometimes no matter what you do it wont...

clip it off, then score it along the fitting a few times to split the pipe. you only lose an inch or two...

it is MADE not to let the pipe out remember!