Advantages to Using Sprinklers in Your Vegetable Garden
During the growing season, sprinklers should provide vegetable gardens at least 1 to 2 inches of water per week. If the soil is sandy, the garden will probably need 2 inches, whereas clay-like soils and denser soils will need the 1 inch of water, whether from natural rainwater or from sprinklers.
Portable Lawn Sprinklers
You don't necessarily need a built-in sprinkler system to be able to irrigate your garden with sprinklers. Portable lawn sprinklers are good enough for most vegetable gardens.
Place the sprinkler somewhere so that all plants will receive good coverage, like with no large plants blocking water from reaching plants in rear rows. Sprinklers that are mounted above plants offer rain-like irrigation that can be great for your garden. This can also prevent a problem with plants blocking the pattern of application.
When using overhead mounted sprinklers, be sure to water early in the day when the air is coolest and calm. This will allow the leaves to dry thoroughly so they won't be damp during the cold of night. Also, early watering lets the leaves continue to absorb water throughout the period of the day when the sun is hottest and can be most damaging.
When using underground sprinklers to irrigate the garden, keep in mind that pop-up sprinklers take 40 or 45 minutes to deliver about an inch of water. Double the time for sprinklers with rotor heads.
How Much Water?
When you use sprinklers to water your vegetable garden, be sure that you wet the soil thoroughly. You want at least the top 3 inches of soil to be wet. You can poke through the soil with your finger to see if it feels dry. Depending on the kinds of vegetables you're growing and how sandy the soil is, you may want to wet the soil up to 5 inches deep.
If you water less than the plants need and the soil only gets wet an inch or 2 down, it prevents plants from growing deep, strong roots. The roots will stay at the top of the soil where it gets wet, and the plants will get weak and die.
How Long to Run the Sprinklers
Since you'll need between 1 and 2 inches of water per week, you should find out how much water you actually apply each day. Get some empty cans of equal diameter and place them in various places throughout your garden.
Run the sprinklers for a single cycle and then check the cans to see how much water is inside. This will not only help you determine how much water pressure to use to ensure that your vegetables receive enough water, but it will show which parts of your garden are getting less water than others. Use this information to help you reposition your sprinklers accordingly.