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Watering the Garden

by Don Janssen, Extension Educator

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Trickle Irrigation

Trickle Irrigation

Sometimes rain comes exactly when you need it; other times - most times - growing a productive vegetable garden means adding water.

Certain times are more critical for water than others. Just after seeds are sown, for instance, you need to keep the soil around them moist. This promotes quick germination and keeps newly emerged roots from drying out.

Newly transplanted vegetable plants generally have very limited root systems. They, too, need frequent watering to help them get established.

Once plants are growing well, the next critical time is when they are flowering and producing the fruits, seeds or tubers that we harvest. Insufficient water when potatoes are setting tubers, tomatoes and peppers are producing fruits, onions are forming bulbs, snap beans are producing pods and sweet corn is being pollinated will mean reduced yields. Dry weather at other times may simply slow or halt plant growth.

Meeting crops' needs for water may mean exceeding the rule-of-thumb 1 inch of water per week, including rain. The kind of soil you have is a big factor in determining how often you irrigate and how much water you apply.

Water moves quickly through light, sandy soils, so they dry out quicker after rain or irrigation than soils with a higher clay content. Because water soaks in rather than runs off, you can apply more water to sandy soils than to clay soils, but you usually have to water more often. Water seeps slowly into clay soils, so you need to water slowly - otherwise the water simply runs off and forms puddles. Once it's wet, clay tends to stay wet.

Plant roots need air as well as water in the soil around them. When too much rain or a combination of rain and irrigation drives all the oxygen out of clay soils, plant roots begin to die. If enough roots die, the whole plant dies.

An advantage of lighter, sandy soils is that it's almost impossible to overwater plants; a disadvantage is that they need frequent watering. An advantage of clay soils is that they hold moisture and don't need such frequent watering. But they can be overwatered.

hatever the soil type, water infrequently - every seven to 10 days if plants aren't in a high-need time - so the soil is moist to a depth of at least 6 inches. Deep watering promotes deep root growth. Shallow watering results in plant roots that remain near the soil surface. There, they're very susceptible to drying out in dry weather.

Techniques for taking some of the time and effort out of watering include trickle irrigation, which applies limited quantities of water directly into plant root zones, and mulching, covering the soil surface around plants and between rows with straw, compost or other organic materials to slow the evaporation of water from the soil. Mulching also helps control troublesome annual weeds. This translates into fewer plants competing for the available moisture.

Hand watering, either by hose or sprinkler can, is feasible in a very small garden, but many gardeners resort to overhead sprinklers to water their plots. Overhead watering is less efficient than trickle irrigation, in that it applies water between the rows and loses significant amounts of water to evaporation. Wetting the foliage can also promote certain plant diseases so use overhead watering irrigation early in the day. The sun and summer breezes can then dry the foliage quickly. Watering in the late afternoon or evening can leave foliage wet all night and provide ideal conditions for some plant diseases to get established.

A method midway between trickle irrigation and overhead sprinkling is use of a soaker hose. Lay it alongside the row and turn the water on so that it barely trickles out of the hose. This will wet the root zone without wetting the foliage or the empty areas between the rows.

(This resource was added July 2002 and appeared in the Lincoln Journal Star Newspaper Sunday edition. For information on reproducing this article or using any photographs or graphics, read the Terms of Use statement)

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University of Nebraska-Lincoln Extension in Lancaster County is your on-line yard and garden educational resource. The information on this Web site is valid for residents of southeastern Nebraska. It may or may not apply in your area. If you live outside southeastern Nebraska, visit your local Extension office