Put a 5 gallon bucket at each tree with a small hole drilled on the side near the bottom and point it at the tree. Fill the 5 gallon bucket from the truck tank as fast as you can and then go to the next one. I'd get a tank with a big hose so you can fill the buckets quick.

The buckets aren't aesthetically pleasing, but they won't be there forever.

Every person should have an interest in life - I think I'll go fishing. ~ Thoreau