Watering tips for vegetable gardens

June 22, 2011

By Debra Levey Larson
Media/Communications Specialist, University of Illinois College of Agricultural, Consumer and Environmental Sciences

URBANA, Ill.—To be productive, vegetable gardens need careful watering, and adequate soil moisture is very important for seed germination, uniform plant growth and productivity, said Maurice Ogutu, a University of Illinois Extension horticulture educator.

“Vegetables need 1 inch of water per week, which is equivalent to about 63 gallons of water per 100 square feet per week during the growing season,” Ogutu said. “The water can be in the form of rain or irrigation. The water source needs to be close to the garden.”

Ogutu said water loss from the garden through evaporation can be minimized by using organic or plastic mulches. Irrigation methods that apply water around the root zone of the plant, such as use of a soaker hose or trickle irrigation, can drastically reduce the amount of water used.

“Some vegetables can tolerate mild water stress without serious negative impact on yield during certain periods of their growth cycle,” he said. “However, all vegetables have critical water-need periods, and inadequate soil moisture during these periods may result in serious yield loss. The critical water need period varies among different kinds of vegetables.”

Following are some of the commonly grown vegetables and the developmental stages when the need for adequate soil moisture is most critical:

– Beans (including lima and snap)—pollination, pod development and pod enlargement

– Broccoli, cabbage, cauliflower—head development

– Tomato, eggplant, pepper—from flowering to harvest

– Dry onions—bulb enlargement

– Cucumbers, muskmelons, watermelons—flowering, fruit development

– Carrots, radish, turnips—root enlargement

– Potato—tuber set and when the tuber is enlarging

– Sweet corn—during silking, tasseling and ear development

with the critical growth stages in mind, these tips can help you achieve higher water-use efficiency in your ve-etable garden:

– Add plenty of compost or manure to your garden before planting to improve the water-holding capacity.

– Plant a small garden that will not require a lot of water.

– Use plastic or organic mulches to minimize water loss through evaporation and to control weeds. Cover the ground with plastic mulch, punch holes in the mulch, and plant vegetable seeds or seedlings in the holes. Alternatively, use organic mulches, such as straw, around the base of established plants.

– Plant early so that rainwater can provide most of the garden’s water needs.

– Space vegetable seedlings so that the ground is well covered in early summer; effective spacing will decrease water loss through evaporation.

– Water in the morning. Set sprinklers above the plant canopy and place small cans throughout the garden to measure the amount of water applied. Early watering helps avoid foliar diseases.

– Place a soaker or perforated plastic hoses with holes underneath organic or plastic mulches and along one side of the plants when placed above the ground.

– Do not water vegetables at mid-day because much of the water will be lost through evaporation.

– Avoid frequent, light watering as this results in shallow rooting. When watering during dry weather, soak the root zone of the vegetables thoroughly with up to 6 inches of water.

If you are starting seedlings outdoors for a late-summer or fall garden, follow these guidelines:

– Prepare the seedbed with a shovel or rototiller. Uniformly apply 1/2 to 1 inch of water on the seedbed. Let the topsoil dry, and then work the soil shallowly with a rake.

– Seed the vegetables. If it doesn’t rain within two days, apply 1/2 inch of water followed by similar applications every other day until seeds germinate.

– Try shading the seedlings from sun scorch.

From the June 22-28 issue

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