When it comes to watering the lawn, you have a choice "to water or not to water" as explained in my last column. However, when it comes to watering the vegetable garden, your only choice is to water. Water makes up 80 to 90% of their fresh weight, so vegetables should never be short of water. Water affects yield, fruit size, and quality. It also prevents a variety of disorders such as toughness, off-flavor, poor filling of pea and bean pods, cracking, blossom-end rot, and misshapen fruit.
Besides the first few weeks after seed germination and immediately after transplanting, vegetables have certain "critical stages" in their growth and development when water is extremely important. For example, lima, pole, and snap beans need water when they're flowering. Sweet corn should have adequate water available during silking, tasseling, and ear development. Keep cucumbers and squash well-watered during flowering and fruit development. The same advice applies for eggplant, pepper, and tomato which require water from flowering until harvest.
The rule of thumb for watering vegetable gardens is simple: vegetables need an inch of water per week in the summertime, whether it's provided by you or Mother Nature. This converts roughly to six gallons per square yard per week. This inch of water will wet the root zone to a depth of 6 to 8 inches.
Don't wait for your vegetables to signal their need for water with wilted leaves or young leaves that have become dull-colored, darkened, or grayish. They could already be injured when they show these signs of drought stress and their yield and quality could already be compromised.
Monitor weekly rainfall amounts and check the soil for moisture. With a trowel dig down 2 to 4 inches deep and feel the soil. With some of our Piedmont clay soils you'll find that simply not being able to dig down easily is enough to know that it's dry.
• Shallow-rooted vegetables will have a greater demand for water than deep-rooted crops, so keep a watchful eye on them. A few shallow-rooted crops include lettuce, corn, potato, and radish.
• Moderately deep-rooted vegetables include bean, carrot, cucumber, eggplant, cantaloupe, pepper, pea, summer squash, and turnip.
• Deep-rooted vegetables include asparagus, lima bean, pumpkin, winter squash, sweet potato, tomato, and watermelon.
You can irrigate your vegetable garden with a variety of tools: a watering can, a garden hose with a fan nozzle or spray attachment, a moveable lawn sprinkler, a soaker hose, or drip or trickle irrigation. If you want to be conservative about the amount of water you want to apply to your vegetables, consider drip or trickle irrigation which is the most efficient irrigation method available. For more information about watering your vegetable garden, purchase a copy of Irrigating your Lawn and Garden, EC 580, for $2.00 from your local Clemson Extension office or from the Web at http://www.clemson.edu/psapublishing/
To help conserve moisture in the soil, maintain a shallow layer of mulch around your plants. Before you start your fall vegetable garden next month, add organic matter to the soil. Organic matter such as compost increases the moisture-holding capacity of the soil.
Finally, when you water your vegetables, don't go overboard and give them more than necessary. Besides being wasteful, excessive watering leaches nutrients out of the soil, encourages diseases, and reduces flavor, especially in cantaloupes and watermelons.
Although keeping up with the watering needs of your vegetables may be an unglamorous chore like weeding or picking off tomato hornworms, it'll be worthwhile at harvest time. Your vegetables will not only have the look and size of those in the supermarket, but they'll have that home-grown, fresh-picked flavor.
--Bob Polomski, Extension Consumer Horticulturist--Clemson University.
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