Do those SIPs have instructions, saying how much water is in the reservoir? This is a good thing to know, to figure out how frequently to water. Here is my experience, and methods, for adjusting this, depending on the plants, and the various SIPs.
My old Earthboxes look much like your SIPs, but with a fill tube, not a side filler, just a small side overflow. These have a 2 gal reservoir, but more recent ones are 3 gal, so they learned that larger is better, up to a point. I learned the first year that planting 4 cucumber plants, as Earthbox recommended on their website, the soil would be totally dried out in less than a day, and this was with a plastic cover! 2 large tomatoes would also dry them out, while 2 cherry tomatoes wouldn't dry them, despite having large vines.
So I set up my drip lines, with 2 gal/hr emitters, to go into the fill tubes, on a timer, to go on twice a day, and initially, I watch to see how long it takes to get the containers to just start overflowing, then 12 hrs later, I check the depth of the water by sticking a dry bamboo stick in the fill tube. Early in the season, since plants are small, and it's cooler, I don't have to water every day, but once it gets hot, and plants are getting larger, I have to do it, twice a day, to prevent overflow - just run it 20 minutes each time, maybe a little more, which would be about 1 1/3 gal per day, but when it gets very hot, it will need to be increased, and I do that by increasing it to 3 times a day, instead of increasing to the point of overflowing - this way, I don't waste water. The homemade SIPs I made to have much larger reservoirs, and only run those timers twice a day, even in extreme heat. The cucumbers I grow in bucket SIPs, which have a lot more water, for just one plant.
Here's one of the first ones planted this year, showing the cover I put on, and how I tuck it down the side. This way, any rain is not wasted! And you can see the watering system - you definitely don't want to water all those by hand!
One of the SIPs with tomatoes, planted on 5-1, Big Beef on L, Brandy Boy F2 on R. by
pepperhead212, on Flickr
Here's one from a couple years ago, with 2 cherries, in late May - not even a month after planting!
Cherry Bomb 5-29. by
pepperhead212, on Flickr
And here are some cherries, on just 6-16 the year before. As you can see, you don't need to grow dwarfs!
Cherry tomatoes, on just 6-16 by
pepperhead212, on Flickr
).
