Vegetables prosper when the surrounding soil is kept quite moist, but frequent overhead watering tends to encourage rust, mildew, blossom damage and disease. Closely spaced drip emitters, drip tape, or porous pipe can balance these requirements by thoroughly watering an area of soil without wetting the leaves.
A 1/2 GPH emitter will generally suffice for an area 16 inches in diameter. In coarser soils, 1 GPH emitters should be used for more lateral coverage. If plants are more widely spaced and deeply rooted, such as tomatoes, squash, etc., a single emitter can be placed at the base of each plant. For row crops, such as carrots, radishes, etc., a drip tape, driperline™, Laser Soaker Line™, or Porous Pipe™ will give a continuous wetted pattern down the rows.
Drip tape and driperline can be run straight down rows for lengths up to 100 feet. However, laser soaker line can only be run in lengths up to 15 feet, but can be wound around plants or around corners. Row crops similar to those listed above can be planted two or more deep on each side of the lateral line. With plants such as corn, strawberries, and peppers, one row on each side of the lateral line is preferred.
If intensive bed gardening is employed, the drip system should be set-up on a grid with laterals 18 inches apart and emitters placed every 
12 inches on the lateral lines. If the bed is 4 feet wide, three laterals will give complete coverage. A system set-up like this one does not need to be changed when planting changes. However, driperline, laser soaker line, and porous pipe will give a continuous band of surface moisture, while an emitter system allows you to add emitter or sprays at desired intervals. It should be remembered that, if you are planting seeds in your garden, emitters alone will not adequately germinate the seeds unless supplemented with over-head watering with either micro-sprays or micro-sprinklers. Once seedlings are established, overhead watering will not be necessary.