Basics you need to know about watering tomatoes: http://www.tomatodirt.com/watering-tomato-plants.html
Pinner said..Drip irrigation- A pinner wrote: I do this every year and it works great! Especially during a long Texas drought- less water waste. The only thing that kept my plants going, and once the plants get growing they hide the bottles. Quick and easy way to fertilize too! Should work well in Arizona too!
I imagine this would work well when "watering in" any new plant on a slope, not just tomatoes. "In a sloped garden space, two plastic containers create a double ring around a tomato plant, which was started indoors and transplanted. The ring channels the water straight down, encouraging the roots to move into the native soil."