I am not a drip irrigation expert but I stick with 1/2 gph emitters. If the plants need more water I just run it longer. The only thing you would be in danger of is not getting enough water to the corn when running the drip 24 hours a day... but that won't come close to happening even with 1/2gph drips.

I just put in a strawberry patch with 1/2gph emitters on 1 foot spacing under plastic mulch. I started with 45 minutes twice a day with a well pressure of 40psi. After 2 days I had mushy mud under my plastic mulch. I turned off the system for 2 days to let it dry out a bit then put a 10 psi pressure regulator on the supply line. I then tried 5 minutes twice a day and the ground dried out too much. I then went to 10 minutes twice a day and this worked really well for a couple of weeks. Just yesterday I upped the timer to 15 minutes twice a day for a little more moisture since the weather is getting really hot.

My numbers are going to be totally different from yours. I used plastic mulch to minimize water usage by minimizing evaporation. The plastic mulch is also supposed to promote plant growth by warming the soil. My soil is very porous volcanic ash. Water settles down through the soil very fast. I added a few yards of compost, many bags of peat moss and several bags of perilite all to help my soil retain moisture. This whole system is a first for me this year and figuring out the watering pattern has just been trial and error.

My recommendation is to start with 10 minutes twice a day and keep a close eye on the soil. Give it a couple of days then dig into the soil a bit and evaluate the moisture then adjust from there. Most adjustments seem to take a couple of days to settle to the point the adjustments can be evaluated.

Whether it is a 0.5 gph or a 4.0 gph we can both get the same amount of water just by regulating how long a run is going to take. My soil is a lot different from yours, maybe a clay loam (heavier to loam) to which I have added a good bit of grape pomace compost and goat manure. I now mulch with screened wood chips from a big pile an arborist truck left for me. Black plastic would be more effective and I can see weeds - and bermuda grass - already trying to poke their heads up through what I have already laid on, but I like the idea of an organic mulch. We'll see.

The great thing about gardening is you can do it how ever you want. :-) There is nothing wrong with 4gph drips. My first drip run in my garden had .5gph, 1gph and 2 gph emitters... that was quite a hassle! Now I just use all .5gph and life is easier. I think my point was that I wouldn't go through the hassle of replacing the 2gph emitters with 4gph emitters.

I was actually worried that 1 foot emitter spacing would be too far for my very porous soil and I would have large dry spots between emitters which is why I added the perilite... for water retention. Now that the system is up and running the whole raised bed is staying nice and moist but not wet. I didn't plant my strawberries right on the emitters either. I had 3 ten year old girls helping me so I was happy to just get the plants in the ground in one piece. I am actually kind of interested to see if the plants close to the emitters do better than the ones between the emitters.

My Strawberry patch is far from the street, between the house and the shop. I did a lot of reading before I went with the black plastic but I sure wouldn't want it where anyone could see it! Black plastic is pretty ugly to me! I like the look of natural mulch MUCH better! This strawberry patch is kind of an experiment for my daughter and me.