Growing vegetables in a drought year
Water rationing in drought years can leave home vegetable gardeners wondering what to do. Water is obviously essential for vegetable growth. Vegetables are mostly water: an ear of corn is 70 percent water, a potato is 80 percent water, and a tomato is 95 percent water. Vegetables will not grow and yield without consistent, even watering.
When water is scarce, the vegetable gardener needs to make wise decisions. This year you may want to limit the size of your garden – if you grew four tomatoes last year, you might want to grow just one or two this year. Instead of growing beefsteak tomatoes – which require 90 or more days to reach harvest – you may want to grow smaller, mid-season tomatoes which are ready in 70 days.
Watering tips for vegetables
• Most vegetables need an inch of water per week. That is about 62 gallons for each 100 square feet; this amount will soak down to about 8 inches in the soil. Use a rain gauge to be sure your crops are getting the water they need.
• The best way to water is to deliver water to the base of the plant: hand water with the hose or use drip irrigation or small trenches that will allow the water to flow and seep into the ground.
• Drip and trickle irrigation systems are very efficient and can place water very near plant roots. These systems have drip heads that can measure the amount of water delivered to the garden.
• The amount of water needed will depend on the type of soil in the garden. Clay soil will hold more water than sandy soil and require less watering. Soil rich in organic matter is best; it is moisture retentive and drains well. Vegetables grown in containers require frequent monitoring and may require more frequent watering.
• Plants with healthy root systems will need water every five to seven days on average unless the weather is hot or windy; temperature and wind can affect the soil’s water-holding capacity.
• Shallow-rooted vegetables require more frequent watering.
• The best time to water is in the morning as plants begin to use water during the day. Watering in the heat of the day will result in loss of water due to evaporation. Watering in the evening can lead to foliar diseases if foliage does not dry before nightfall.
• Water when the air is still. Watering in windy weather will mean greater evaporation.
• Lightly cultivate around plants before watering, but not deeply; this will allow the soil to accept and retain moisture.
• Watering to a depth of 5 to 6 inches encourages the growth of deep roots. Avoid quick, shallow watering which encourages shallow root growth. Shallow roots are more susceptible to damage by the sun and heat.
• Water before plants become wilted and stressed. When plants wilt the damage may already be irreversible. Plants that are wilted in the morning need water immediately. Check the soil moisture every day or two to make sure the soil is moist, not dry or too wet.
• Do not over water. Too much water can leach nutrients from the soil and drown plants; plant roots require oxygen from the soil to help them grow.
• Mulch around plants to conserve soil moisture. Add aged compost and organic matter to the soil regularly. This will increase the soil’s moisture-holding capacity.
• Do not let weeds grow in the garden. Weeds compete with vegetables for water and nutrients.
• Harvest vegetables when they are young and just ripe. Young vegetables will require less water and will be more tender and tasty than vegetables that sit in the garden past their peak.
Tips for specific crops:
• Beans: During pollination, flowering, and pod development, blossoms may drop and pods may fail to enlarge if watering is inadequate; 1 gallon per week per foot of row.
• Germinating seed: Water frequently to keep the soil moist but be careful not to wash away seed.
• Greens: Consistent even moisture through the season; leaf crops are shallow rooted and need frequent irrigation; one gallon per foot of row, or two to three gallons per square yard a week, nine inches per season; where regular watering is difficult, do a heavy watering of four gallons per square yard every 10 days.
• Herbs: Keep soil just moist, not wet; herbs do best with less water; wait until they begin to wilt; 1 gallons per plant per week at most.
• Melon: During flowering, fruit set, and fruit development; 1 gallons per plant per week or 18 inches per season.
• Pepper: Even, consistent watering from planting to fruit set and enlargement; one pint per plant a week when young, increasing to 1 gallons per plant a week or 18 inches per season.
• Seedlings: Keep seedlings evenly moist, but avoid too wet soil which can cause damping off; water to avoid wilting early in the plant’s life.
• Squash: Even, consistent watering during bud development, flowering, fruit development; 1 gallons per plant per week or 18 inches per season.
• Tomato: Consistent, even watering is critical during flowering, fruit set, and fruit enlargement; 2 gallons per plant each week or 24 inches per season. More water may be needed for unmulched plants. Older, late-maturing varieties may require less water near harvest.
• Transplants: Keep transplants evenly moist; water to avoid wilting as roots develop and take hold; the first five days are critical.
Steve Albert is the author of The Kitchen Garden Grower’s Guide available at Amazon.com. He teaches in the landscape design program at the U.C. Berkeley Extension. He lives in Oakmont.