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Colorado Master Gardenersm ProgramColorado Gardener Certificate TrainingColorado State University ExtensionCMG GardenNotes #714Irrigating 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 5Garden 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 714-1
can be mmisleading to the novice. O compacted clayey soils it may be so On s, omewhat difficult when moist and very diff t ficult when dr On sandy soils, it may be ry. somewh easy wet o dry. hat or To chec moisture le ck evels, a soil pr robe is a usef tool to pull up ful l soil sam mples from the rooting zone at a six to ei e e ight inch dept A th. small ga arden spade ccould be used. . Housepl watering meters are he lant elpful in evaluating the soi il moisture content und mulch. Re e der ealize howeve that these er, inexpennsive meters a somewhat inaccurate. I the fertility level are If y is high, the meter wil read on the wet side. If t fertility is low, ll the s the mete will read on the dry side Learn to in er n e. nterpret the m meter reading for a specific soil by trial and error. [F c Figure 1] Figure 1. Although somewha inaccurate, a houseplant w at water meter is a tool to evaluate wa needs in th garden. l ater heAutomate the Sy m ystem with C Controllers Sprinkle or drip syst er tems can be eeasily automat with a mu ted ulti-zone cont troller like the lawn A small ga n. arden could be connected t the lawn’s controller as a separate to zone and run on a dif d fferent progra am. However do not have the lawn and r, e d vegetable garden on t same zone, as water ne the eeds are not th same. he Single z zone controlle connect to the garden h ers o hose. Some si imple models are s manuall turned on a automatic ly and cally turn off after the set n number of min nutes or gallons. More elabor battery op rate perated mode turn the water on and off at the els day and time interval set by the ga d l ardener. [Figure 2] Figure 2. Sing zone contro gle ollers connect t the hose line Left: This sty to e. yle is manually turned on and au utomatically tur off the wate flow after the rns er e set number of minutes. Righ This battery powered contr ht: roller turns wat ter on and off at the day and tim intervals set by the gardener. me 714-2
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. 714-3
A disadv vantage of a d system is that they req drip s quire relativel clean water ly r.Systems readily plug with dirt, alg or salts in the water. T is genera not a s g gae, n This allyproblem when using drinking quality municipa water suppl m al lies. Dependi on ingwater qu uality, drip irr rigation may not practical for many non n-potable wat tersources. The filtering system requ . g uired may be expensive an high mainte nd enance.Ideally, an in-line dri hose or soa ip aker hose is placed on the s surface u soil under themulch. The soaker h hose may also be buried a c o couple of inch into the so to hes oilprotect t hose from breakdown b sunlight. the m byOn a raiised-bed box, space the dri line/soaker hose at 12-in spacing. A four- ip r nchfoot wid box would have four run of the drip line/soaker h de ns hose up and d down thebox (as illustrated in Figure 1). Fo larger vege or etables like co squash, a cole orn, andcrops (th plants ac hree cross a four-fo wide bed) make three r oot ) runs up and d down afour-foo wide box. On a two-foo wide raised bed box for t ot ot d tomatoes or b beans, thedrip line e/soaker hose runs down an back. [Fig nd gure 3] Figure 3. On t this four-foot wide box, the drip line or r soaker hose m makes four runs up and down the box at 12-inch spacin ng. Carrot rows ar re running across the s box.Drip sys stems are designed to run o low pressu on ure. High pre essure may sp the plithose and pop connec d ctions. The deesired low preessure is easy to achieve w y withpressure regulators th have hose e hat e-end fitting (f found with th drip system he msupplies If the gard has chang s). den ging elevation a pressure regulator wil be ns, llneeded for every cou of feet ch uple hange in eleva ation. [Figure 4] e Figure 4. With h irrigation pipe, it is , easy to plumb a b tap at each raised bed box. Here ae pressure regulator with hose-end fittings reduce es pressure to 25 5 psi. It is connected to a ½- inch soaker ho ose. 714-4
Determi the run tim by examin ine me ning the soil m moisture content. Run tim will me vary wit the brand o hose, water pressure, and spacing. th of rSoaker Hose and Soaker Tu e d ube The soa aker hose and soaker tube t type of drip sy ystem allows water to seep out the p entire le ength of the h hose. It is easy to use in tra y aditional row style or raised-bed gardens. [Figure 5] Figure 5. Soaaker hose seeps wa ater out along the l length of the hose. It can be connected b manually c e by connecting the garden hose to each line at each e e irrigatio session or b connecting a series of d on by g dedicated gard hoses to a series of den lines. O raised-bed gardening, it is easy to run a water line with a tap to each box. On t n e o Several small boxes m run together on the sa zone. [Figure 4] may ame For unif form water deelivery, keep r runs short, ge enerally 25 fe or less. W long eet With lengths, water deliver will be hig ry gher at the top of the hose l and less a the p line at bottom. The ground must be reaso onably level. On slopes, r several sh run hort lengths. tyles are available in the home garden t Several brands and st trade. • Half-Inch So oaker Hose – Some brand (like Swans Soaker Hose are a ½- ds s e) inch hose tha connects w standard h at with hose fitting. T These are fou the und garden hose section. It ca be cut to an length and connected w garden an ny d with . hose fittings. A small plast disc fits in tic nside the fema hose conn ale nection as a prressure regulator (acctually a flow regulator). W the reduc water flow it may With ced w, need to run f around an hour to adequ for uately water t garden. It works the t better to use the pressure rregulators with hose-end ffittings found with the drip irrigatio supplies (fi on igure 4). With this type of regulator, the drip line h f runs 10-20 m minutes to adeequately water the garden. Without a pr ressure regulator of ssome type, th soaker hose tends to rupture sending out steams he e of water at sp rather tha dripping a pots an along the line. . This half-inc hose style i more tolera of small am ch is ant mounts of dir algae, rt, or salts in the water than o e other types of drip systems and may be f s, e successful on some nonpo n otable water s sources. Perio odically, open up the n end of the ho and flush out soil deposits. ose 714-5
• 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 ContainersAuthors: David Whiting, with Carol O’Meara and Carl Wilson; Colorado State University Extension. Artwork byDavid 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 714-6