Jack,
If you're planning on buying a mulch layer then you're farming on a much larger scale than I am.
I've never seen how the lettuce growers plant under the plastic mulch (or if they do) but I just assumed it was by growing the seeds in plugs and then plugging them in through slits in the plastic (and next to the tape). I've seen some field flower growers use this method - usually to keep the critters from eating the seeds before they germinate. And yes, if seeding in sandy soil I think it would be necessary to walk the line for the first waterings to make sure there are no dry/bare spots. For short season crops plastic mulch might not be a desirable or cost effective option. Maybe some "real" farmers will chime in on this.
Also, I seem to remember reading that the thicker wall drip tape was recommended if you are burying it more than a few inches. Not sure the reasoning there - I bury the cheap tape an inch or two by when I "lay by". Usually, though, I end up digging it out to repair the gopher holes...
|