If you want to have only one spacing, one year ago, I would have said 12 inch. However, I tried 8 inch and I am never going back. You get much better coverage between emitters. This closer spacing works better with root crops like carrots/radishes/turnips, etc.

Jay

I agree with Jay. I need to order a new roll of driptape and I believe I'll go with Aqua-Traxx with 6" spacing, .67 GPM per 100'. For clay soils the emitter spacing is less of an issue but I see advantages to closer spacing. Oddly the tape price is more closely related to tape thickness than emitter spacing. So for your mixed row crops the closer spaces emitters is ideal.

Thanks all. I was leaning towards the closer spacing, and its good to hear others' experience. I'm going with just one spacing because I need about 1000 ft, and it seems like that is a good price point for bulk rolls as opposed to buying several different rolls. Also easier to keep track of what I've got where.

One farmer I talked with mentioned he always planted transplants no more than 3" away from an emitter. He had sandy loam soil.

In my backyard clay soil, I've measured the water dispersing about 5" away from an emitter at a depth of several inches. I was not as much as I had expected. I gave away all my rolls of 12" emitters and got 6" ones.

i use 12" spacing. i get good results.

The summation of responses seems to be that any of the closer spacing tapes will be OK. I mentioned that I would be buying closer spacing tape but this year I useed 7 rows of each 8" and 12" spaced emitters in the same high tunnel and I could not tell any real difference with tomatoes. You will likely see more differences with sandy soils and with row crops like onions, carrots, beets. You might even be better to use a wider spacing if you think you can turn the water off as soon as wetting paterns meet.