I would think under if the drip holes are tiny
cuz in the heat of summer the cardboard could dry out
and get brittle in places and it would just suck the water
up from the drip.

But what do I know just a guess.

Tree

I'd put it under the mulch so that the moisture soaks into the ground and not just into the mulch. Having it under the mulch also will reduce the amount of moisture lost to evaporation.

If rainfall remains low and fire danger remains high, you'll need to water the mulch every now and then too so it won't be tinder-dry.

I don't use cardboard (would if I had it). I have tried placing the tubes on top and on bottom. I think I like on top a little better because I can see the amount of water flow I having going to my plants.((I like the 1/16 dia. holes pointing up to keep sediment from clogging the holes, on the side works OK also)

There will be a little more lost to evaporation but I think the amount is small because I place the tubes close to the plant so the water that remains in the tube will not heat up from the sun. I like a ball valve for each tube and the water adjusted to go about 2 or 3 inches high. What I describes is how I do okra, tomatoes and peppers. Beans, peas and most other veggies I plant closer together and run the tube down the center between rows.

As I get to having more mulch I may change.

I really don't think there's a wrong way to do it.

I hope to start adding my tubes and mulch in a week or so.
I am running behind on that to.

Larry

Thanks to you all! I think maybe I've got it figured out....

Tree - you're right. I hadn't thought about the cardboard getting brittle in the heat so Good Point!

Larry - I took a lot of notes from you last year and we use the 1/16 drill bit too. With tomatoes & peppers, we also try to put the pipe right next to the plant. That's what we've done in the raised beds. Also like you, I was thinking putting the pipe in the middle of the rows of beans & okra would work better.

Dawn - with this weird weather - who knows what the heck to do??? We usually try to water the mulch down every once in a while just to keep it in place.

I think what we'll end up doing is laying the pipe between the rows of beans, peas & okra. Point the holes over on their sides. Lay the cardboard over that, then lay mulch over the cardboard. A few good rains will probably soak it all down really good so it will hold and hopefully, everything will be happy & grow!

You sure are being optimistic...."a few good rains"? lol

I hope you get a few good rains. Or even a whole lot of good rains.

Paula,
I also thinking to build PVC pipe irrigation system similar what you have built. I need to build that system for 14 new beds. I just wonder is that PVC or pre-holed dripper pipes are economical? I would like to know more about your system. Regards -Chandra

Over time, UV rays will degrade your PVC pipe. Put it under the mulch. Water the mulch on top as needed. Your total water usage will be less this way because you shouldn't have to saturate your cardboard everytime you water in order to get water to the plants.

I use dripworks.com products. Love the products, love the service. Easy to assemble, easy to store, easy to use. THEY should have the copyright on the EASY button.

If you use the grey electrical PVC (you see it on the side of utility poles and on housed) it is UV resistant and a little cheaper where I live.

Chandra, you can drill the holes anywhere you want them.
I have experimented with .015 to .093 dia. The 1/16 hole (.062) works fine for me.

Larry

Larry - the grey stuff? Sheesh....and here I have all this white stuff! LOL! BTW - that grey stuff is what they ran the plumbing under my home with...and it DOES NOT hold up.

Chandra - I'll drop by soon and I'll share what I've learned, but I agree with Larry - the 1/16th drill bit is the best overall to use.

Paula

Paula, I hope they did not run regular water lines with electrical PVC, it has formed fitting on the end (why its cheaper to use) and will blow apart easier under static pressure, but you wont get that in a drip system. There is less than a pound of pressure on my system down stream from the ball valve.

Now if you are talking about the stuff used in mobile homes, that is a different breed of duck altogether. I would never use that because it cost too much. I have thin wall white PVC, sch. 40 white PVC and sch 40 grey PVC. My system is 8 years old now and the only problem I have had is with the thin walled. Even my headers are made with grey PVC, but I used the white fitting on it. At times they are subjected to 45 pounds of pressure if I am running the water hose off of them. You must always prime the joints in all PVC before you glue them to get the strongest bond.

Larry