CMG GardenNtes #265 Methds t Schedule Hme Lawn Irrigatin Outline: Irrigatin scheduling, page 1 Sprinkler-type methd, page 2 Precipitatin rate methd, page 3 Adding cycle and sak features, page 5 Observatin and manual cntrl methd, page 5 Using emerging technlgy, page 6 ET cntrllers, page 6 Sil misture sensrs, page 6 Rain shut-ff devices, page 7 Fine-tuning any schedule methd, page 7 Irrigatin Scheduling In many areas f the semiarid West, gardeners cannt cunt n natural precipitatin t deliver misture at the right times r in sufficient amunts t grw mst intrduced landscape plants. Supplemental irrigatin is necessary unless the plant pallet is limited t species tlerant f natural precipitatin levels. Due t limited precipitatin and peridic drughts that limit available water supplies, using efficient irrigatin is f interest t all. Scheduling landscape irrigatin is a critical part f lawn and garden care. When irrigating, gardeners have tw gals: 1) water enugh t keep plants healthy, and 2) minimize water waste. Irrigatin management cmes dwn t tw basic questins: 1) hw much, and 2) hw ften. Gardeners ften hear recmmendatins such as water deeply and infrequently r water t adequate depth withut runff. Such advice is usually t brad t translate int effective irrigatin management practices. Rather than using brad generalizatins, this CMG GardenNtes lks at several management appraches with differences in the time investment and ptential water savings. The textbk figures will need t be fine-tuned t the specific site needs, taking int accunt sils, expsure, heat, wind, and ther water-use factrs. Methds fcus n cl-seasn turf, such as Kentucky bluegrass and turf-type tall fescue. Xeric and dryland plants may need significantly less water. 265-1
Sprinkler-Type Methd One f the easiest ways t schedule an irrigatin system is based n sprinkler type. Different types f sprinklers deliver very different amunts f water in the same amunt f time. By cnsidering sprinkler type, gardeners can begin t match their watering practices t the lawn s water needs. Pp-up spray heads typically apply 1-2½ inches f water per hur, whereas rtr heads nly deliver ¼ t ¾ inch f water per hur. Therefre, znes that have ppup spray heads can run fr a shrt time, while znes with rtrs will need t run lnger t deliver the same amunt f water. A gardener culd estimate that a zne with pp-up spray heads applies 1¾ inches f water per hur, and znes with rtr head apply abut ½ inch per hur n average. Table 1 estimates run time (based n histrical water use). The typical Clrad sil requires that this be split between a cuple f irrigatins. Table 1. Estimated Sprinkler Run Time Based n Sprinkler Type fr Cl-Seasn Lawns Late May & July & Early April June August September Octber Inches f water per week 0.75 1.0 1.5 1.0 0.75 (irrigatin plus rain) Late May & July & Early Run Time (minutes/week) April June August September Octber Pp-up Spray Head 1 Irrigated 1 time per week 3 26 34 52 34 26 Irrigated 2 times per week 4 13 17 26 17 13 Irrigated 3 times per week 9 11 17 11 9 Irrigated every 6 days 22 29 45 29 22 Irrigated every 5 days 19 24 37 24 19 Irrigated every 4 days 15 19 30 19 15 Irrigated every 3 days 11 15 22 15 11 Irrigated every 2 days 7 10 15 10 7 Rtr Head 2 Irrigated 1 time per week 3 90 120 180 120 90 Irrigated 2 times per week 4 45 60 90 60 45 Irrigated 3 times per week 30 40 60 40 30 Irrigated every 6 days 77 103 154 103 77 Irrigated every 5 days 64 86 129 86 64 Irrigated every 4 days 51 69 103 69 51 Irrigated every 3 days 39 51 77 51 39 Irrigated every 2 days 26 34 51 34 26 Percent f July/August 50% 67% 100% 67% 50% 1 Pp-up spray head estimated at 1 ¾ per hur. 2 Rtr head estimated at ½ per hur. 3 Recmmended fr mst Clrad sils in the spring and fall 4 Recmmended fr mst Clrad sils in the summer 265-2
An easy tl fr making seasnal adjustments is the Percent Key fund n mst cntrllers. The cntrller is set fr the July/August irrigatin schedule. The percent key is set at 50%, 67% r 100%, based n the seasn. The methd will need fine-tuning as described belw t match the actual water need fr the site based n sil, expsure, heat, wind, etc. Althugh this methd utlines a starting pint fr gardeners wh want an easy apprach, it des nt factr in the actual water applicatin rates fr each zne. Precipitatin Rate Methd A far better apprach is t d a Precipitatin Rate (Catch Can) Test n each zne t determine the actual water delivery rate (knw as precipitatin rate). The actual precipitatin rate is determined by the sprinkler type and brand, water pressure and head spacing. It is generally slightly different fr each zne. T d the calculatins yu will need six identical, straight-sided, flat-bttmed cans such as sup, fruit, r vegetable cans. (D nt use shrt cans like tuna cans as they are t shallw, and water may splash ut.) Yu will need a ruler, a watch and paper/pen t recrd yur findings. Many water prviders and sd grwers have calibrated plastic cups specifically designed fr this test. Precipitatin Rate (Catch Can) Test Step 1. Place six identical, straight-sided, flat-bttmed cans randmly arund the area between sprinkler heads in the zne. Step 2. Turn n the sprinklers fr exactly ten minutes. Step 3. Pur all the water int ne can. Step 4. With a ruler, measure the depth f the water in the can. This is yur precipitatin rate in inches per hur. Write it dwn fr future reference. Step 5. Repeat steps 1 and 2 fr each irrigatin zne. Step 6. Use Tables 2 & 3 t calculate the run time fr each zne. Nte: if the amunt f water in sme cntainers is significantly mre r less than thers, the system is prly designed r head(s) are malfunctining. In many lawn sectins, ne zne waters the area frm the left while anther zne waters the same area frm the right. In this situatin, cut run times fr znes in half, s that each applies half f the needed water. An easy way t make seasnal adjustments is with the Percent Key fund n mst cntrllers. The cntrller is set fr the July/August irrigatin schedule. The percent key wuld be set at 50%, 67% r 100% based n the seasn. The methd will need fine-tuning as described belw t match the actual water need fr the site based n sil, expsure, heat, wind, etc. Table 2. 265-3
Minutes t Run Sprinklers PER WEEK Based n Precipitatin Rates Fr Cl-Seasn Turf in Clrad Late May & July & Early April June August September Octber Inches f water per week 0.75 1.0 1.5 1.0 0.75 (irrigatin plus rain) Precipitatin Rate 1/4 180 240 360 240 180 3/8 120 160 240 160 120 1/2 90 120 180 120 90 5/8 72 96 144 96 72 3/4 60 80 120 80 60 7/8 52 69 103 69 52 1 45 60 90 60 45 1 1/8 40 53 80 53 40 1 1/4 36 48 72 48 36 1 3/8 33 44 65 44 33 1 1/2 30 40 60 40 30 1 5/8 28 37 55 37 28 1 3/4 26 34 51 34 26 1 7/8 24 32 48 32 24 2 23 30 45 30 23 2 1/8 22 28 42 28 22 2 1/4 20 27 40 27 20 2 3/8 19 25 38 35 19 2 1/2 18 24 36 24 18 2 5/8 17 23 34 23 17 2 3/4 16 22 33 22 16 2 7/8 16 21 31 21 16 3 15 20 30 20 15 Percent f July/August 50% 67% 100% 67% 50% Table 3. Cnversin f Run time PER WEEK t Run Time PER IRRIGATION Irrigatins Per Week Cnversin t Run Time Per Irrigatin 1 time per week 1 minutes per week 2 times per week 2 minutes per week / 2 3 times per week minutes per week / 3 Every 6 days minutes per week X 0.86 Every 5 days minutes per week X 0.71 Every 4 days minutes per week X 0.57 Every 3 days minutes per week X 0.43 Every 2 days minutes per week X 0.29 3 Recmmended fr mst Clrad sils in the spring and fall 4 Recmmended fr mst Clrad sils in the summer 265-4
Determining the number f irrigatins per week becmes cmplex as sil waterhlding capacity and rting depth are factred in. Fr details, refer t CMG GardenNtes #263, Understanding Irrigatin Management Factrs. Hwever, many gardeners knw by experience hw ften they need t irrigate. Fr the majrity f Clrad sils, irrigating nce per week wrks in the spring and fall, and twice a week wrks in the summer. Watering as infrequently and deeply as the sil allws gives better resilience during ht spells and helps reduce many weed species. Adding Cycle and Sak Features On slpes r cmpacted, clayey sils, water is generally applied faster than it can sak int the sil, resulting in water being wasted as it runs ff-site. The cycle and sak apprach cuts the irrigatin perid int multiple shrt runs with sak-in time in between. Prgramming a cntrller fr cycle and sak is simply a matter f using multiple start times. Adding Cycle and Sak Step 1. Frm the methds discussed abve, calculate the ttal run time fr the irrigatin. Step 2. Using Table 4, figure the number f cycles and saks desired. Fr example, if the run time is 26 minutes, three cycles are suggested. Step 3. Divide the run time per irrigatin by the number f cycles t get the run time per cycle. Fr example, if the run time is 26 minutes and three cycles will be used, run time per cycle is nine minutes (26 / 3 = 8.67, runded t 9). Step 4. Set prgram with multiple start times, as needed. Generally, the cntrller is set t cycle again after all the znes have run. If the cntrller nly has a few znes, start times need t be at least ne hur apart. Table 4. Estimated Number f Cycles t Reduce Surface Runff Type f Sprinklers Run Time Per Irrigatin Number f Cycles Pp-up Spray Heads Greater than 16 minutes 2 Greater than 24 minutes 3 Rtr Heads Greater than 48 2 Greater than 72 3 265-5
Observatin and Manual Cntrl Methd A simple methd t manage lawn irrigatin and cnserve water is t manually activate the cntrller as needed. With careful attentin, this methd can maximize plant health and water savings since the gardener cntinually adjusts the irrigatin system t actual weather and lawn needs. The dwnside f this methd is that it takes daily attentin t the lawn s water needs. Run times n the cntrller are set as previusly described. The difference is that the cntrller is turned t the ff psitin. It is manually activated when the lawn shws signs f water stress (clr change frm bluish-green t grayish-blue and ftprints are still visible an hur r mre later). After the znes run thrugh, the cntrller is turned back t ff. Using Emerging Technlgy Advances in irrigatin technlgy have led t several innvatins. ET Cntrllers and sil-misture sensrs are examples. Even thugh they may be mre expensive r require prfessinal installatin, these prducts can be used t further imprve water delivery t a landscape. Because they autmate the irrigatin cntrller, they can ptentially reduce the amunt f effrt needed t water effectively. ET Cntrllers The ET cntrller is a relatively new piece f equipment that autmatically adjusts the irrigatin t the daily ET. ET cntrllers are designed t water nly enugh t fulfill the lawn s water need, thereby reducing ver and under watering. Sme mdels use Histrical ET, which is a multi-year average fr the day. With these, dry spts will pp up with extreme heat ver multiple days. They d nt take int accunt actual rain received lcally. Fr a small annual fee, ther mdels cnnect by cell phne, Wi-Fi, r satellite cmmunicatin netwrks t dwnlad actual ET and rainfall frm a lcal weather statin system. On a day-by-day basis, they adjust the irrigatin t match actual water need. Fr additinal infrmatin n ET cntrllers and the use f ET in irrigatin management, refer t the Nrthern Clrad Water Cnservancy District website at www.ncwcd.rg. Sil-Misture Sensrs Sil-misture sensrs measure the water cntent f the sil, allwing the cntrller t run nly when sil dries dwn t a threshld level. One f the advantages f a sil-misture sensr is that it uses n-site sil cnditins t cntrl the irrigatin system. Usually ne sensr is buried in the hme landscape in a representative area. Run times fr reduced irrigatin znes r shady znes are prgrammed int the cntrller relative t the representative zne. 265-6
Rain Shut-ff Sensrs Rain shut-ff devices, als knwn as rain sensrs, interrupt the schedule f an irrigatin cntrller when a specific amunt f rain has fallen. They are wired int the irrigatin cntrller and placed in an pen area where they are expsed t rainfall. They save water by preventing an irrigatin system frm running during mderate and heavy rains. Many states, but nt Clrad, require rain shut-ff sensrs n autmated systems. Fine-Tuning Any Scheduling Methd Any scheduling methd will need fine-tuning t match the actual water need f the site based n sil type, expsure, wind, heat, rting depth, etc. This is dne by careful bservatin f the lawn. When adjusting all znes, the Percent Key n mst cntrllers prvides an easy methd t fine-tune fr the actual site by adjusting the percentage up/dwn in 10% increments, as needed. The key can als be adjusted by increasing/decreasing the run time fr each zne in 10% increments, as needed. When adjusting a single zne, adjust the run times fr that zne up/dwn in 10% increments, as needed. In typical summer weather, if the lawn starts t becme dry between irrigatins, increase the run time in 10% increments, as needed. By trial and errr, it is easy t fine-tune each irrigatin zne. On multiple days f unusually ht weather, dry spts shuld pp up if the cntrller is precisely fine-tuned. In unusually ht weather, if dry spts d nt pp up, the lawn is being ver-watered. Cut back the time in 10% increments, as needed, t fine-tune each zne. Many water prviders encurage hmewners t water their yards between 9 p.m. and 9 a.m. Winds are typically less at night, and evapratin lss will be lwer. Authr: David Whiting, Clrad State University Extensin, (retired). Revisin: Kurt M. Jnes, Chaffee Cunty Extensin Directr (9/2017). Clrad Master Gardener GardenNtes are available nline at www.cmg.clstate.edu. Clrad State University, U.S. Department f Agriculture and Clrad cunties cperating. Extensin prgrams are available t all withut discriminatin. N endrsement f prducts mentined is intended nr is criticism implied f prducts nt mentined. Cpyright 2011-18. Clrad State University Extensin. All Rights Reserved. CMG GardenNtes may be reprduced, withut change r additins, fr nnprfit educatinal use. Revised Octber 2014 & September 2017 265-7