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Colorado Master Gardenersm Program Colorado Gardener Certificate Training Colorado State University Extension CMG GardenNotes #714

Irrigating the Vegetable Garden

Outline: Garden irrigation, page 1 Measuring soil moisture content, page 1 Automate the system with controllers, page 2 Furrow irrigation, page 3 Sprinkler irrigation, page 3 Drip irrigation, page 3 Soaker hose, page 5

Garden Irrigation

In vegetable production, an adequate supply of water during the growing season is directly related to produce quality and yields. Many vegetables become strong-flavored or stringy with water stress. For details on specific water needs of vegetables, refer to CMG GardenNotes #716, Water Conservation in the Vegetable Garden.

Several gardening techniques (including soil preparation, mulching, and efficient irrigation) help conserve water in the vegetable garden. For additional information, refer to CMG GardenNotes #711, Vegetable Garden: Soil Management and Fertilization; #715, Mulches for the Vegetable Garden; and #716, Water Conservation in the Vegetable Garden.

As a rule of thumb, vegetables use around ¼ inch of water per day during typical summer weather. If the garden is watered every four days, apply one inch of water per irrigation. Hot, windy weather will increase water demand significantly. Beans and corn will be significantly higher in water demand during blooming or tasseling/silking.

Checking Soil Moisture Content

Check soil moisture regularly. Irrigate when the top two to four inches of soil is dry to the touch. This is especially important if using mulch, where surface evaporation is reduced.

Evaluating when the soil needs irrigation is rather subjective. The “stick” method (judging moisture by the relative easy or difficulty of pushing a stick or screwdriver into the soil) is an old farmer’s standard. It will be easier when wet than when dry. However, this very subjective method is specific to soil types and

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Furrow Irrigation

For gardeners who have irrigation water from a ditch, furrow irrigation in the traditional row-style garden layout may be most practical. As a rule of thumb, adjust water flow for the furrow so that the water reaches the end of the row 1/3 of the time into the irrigation period. For example, if the irrigation period is 15 minutes, the water should reach the end of the row in five minutes. Soil erosion and runoff are major disadvantages of furrow irrigation.

Sprinkler Irrigation

Sprinkler irrigation is considered more efficient in water delivery than furrow irrigation. It is easy to measure the amount of water applied and easy to manage. Because it wets the entire soil surface, weed seed germination may be high.

Sprinkler irrigation is discouraged on vegetables prone to foliar diseases such as Early Blight (tomatoes, peppers, and potatoes). The splashing water spreads disease organisms and water on the leaves creates favorable conditions for disease development. For additional information on Early Blight management, refer to CMG GardenNotes #718, Tomato Early Blight. Tall crops, such as corn and pole beans may interfere with water delivery patterns.

As a rule of thumb, vegetables use around ¼ inch of water per day, depending on temperature, wind, and stage of crop development. For example, if the garden is watered every four days, apply one inch of water per irrigation. The gardener can quickly learn how long to run the sprinklers by measuring the amount of water in several straight-sided cans placed around the garden.

Delivery rates depend on the type of sprinkler heads used, pressure, and the spacing of heads in the garden. For example, pop-up spray heads deliver around 1½ inches per hour and would typically run 40 minutes to apply 1-inch of water. Rotor type heads deliver around 1/2 inch per hour and would typically run for 120 minutes to apply 1-inch of water.

Because the water needs of the vegetable garden are different from a lawn, it should be on a different irrigation zone than the lawn. Water use will be low in the spring when crops are small and temperature are cool and will increase as the temperatures rise and crops come into bloom.

Drip Irrigation

Drip irrigation is well suited for the block-style garden layout and raised beds. Several different types of drip systems are available including:

o In-line drip tubing – Emitters are found in the tubing every 6, 12, or 24 inches; 12 inches is most common in the home garden trade.

o Soaker hose and soaker tubing – Emits water along the entire length of the hose.

o Bubblers and drippers – Emitter or drippers are placed to water individual plants.

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• Quarter-inch Soaker Tubing – A ¼ inch soaker tubing is availble in the drip irirgaiton section at garden stores. Cut the soaker tubing to desire length and connect with drip system components. An in-line pressure regulator (figure 4) is required; otherwise, the fitting may pop or leak.

Because the soaker tubing has a higher delivery rate, it can not be on the same zone as other in-line drip hoses, button emitters, or bubblers.

Additional Information – CMG GardenNotes on vegetable gardening:

#711 Vegetable Garden: Soil Management #718 Early Blight of Tomatoes and Fertilization #719 Vegetable Garden Hints #712 Sample Vegetable Garden Seed Catalogs #720 Vegetable Planting Guide #713 Block Style Layout in Raised Bed #721 Sample Planting for Raised-Bed Garden Vegetable Gardens #722 Frost Protection and Extending the #714 Irrigating the Vegetable Garden Growing Season #715 Mulches for the Vegetable Garden #723 Growing Vegetables in a Hobby #716 Water Conservation in the Vegetable Garden Greenhouse #717 Growing Tomatoes #724 Vegetable Gardening in Containers

Authors: David Whiting, with Carol O’Meara and Carl Wilson; Colorado State University Extension. Artwork by David Whiting. o CMG GardenNotes are available online at www.cmg.colostate.edu. o Colorado State University, U.S. Department of Agriculture and Colorado counties cooperating. o Extension programs are available to all without discrimination. o No endorsement of products mentioned is intended nor is criticism implied of

products not mentioned. o Copyright 2003-2012. Colorado State University Extension. All Rights Reserved.

CMG GardenNotes may be reproduced, without change or additions, for nonprofit educational use.

Revised January 2012