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Irrigation
scheduling with subsurface drip
uses the same methods of calculation as above-ground irrigation.
The subsurface grid system is designed to wet the irrigated area
completely by methods similar to those used in above-ground
irrigation, supplying water in inches per hour. For efficient
water application, it is necessary to apply water rates equal to
or less than the rate at which the plants use water
(evapotranspiration rate; ET). The ET rate is expressed in inches
per unit of time, thus our application rates are expressed in
inches per hour. (For regional ET data, refer to the Toro
Rainfall and Evapotranspiration Data Book, Form No. 490-1358.)
The following formula is used to
determine application rates for subsurface drip irrigation.
Application rate (inches per hour)
= 231.1 x Emitter flow (GPH)
Dripper spacing x Dripline spacing (in inches)
|
| For example: |
Dripline row spacing = 12"
DL2000 emitter spacing = 12"
Emitter flow rate = .53 GPH |
| 231.1
x .53 GPH |
= |
0.85
inches per hour |
| 12
(inches) x 12 (inches) |
Or, use the Water Application Rate Table
below to determine application rates.
TABLE 3.1
| WATER
APPLICATION RATE IN INCHES PER HOUR @ 20 PSI |
| |
Item
Number |
Flow Rate |
Dripline
Spacing |
| 12" |
15" |
18" |
24" |
| Pressure-Compensating
|
RGP-212-01 |
0.53 GPH |
0.85 |
0.68 |
0.57 |
0.43 |
| RGP-212-03 |
0.53 GPH |
0.85 |
0.68 |
0.57 |
0.43 |
| RGP-212-10 |
0.53 GPH |
0.85 |
0.68 |
0.57 |
0.43 |
| RGP-218-01 |
0.53 GPH |
0.57 |
0.45 |
0.38 |
0.28 |
| RGP-218-03 |
0.53 GPH |
0.57 |
0.45 |
0.38 |
0.28 |
| RGP-218-10 |
0.53 GPH |
0.57 |
0.45 |
0.38 |
0.28 |
| RGP-224-03 |
0.53 GPH |
0.43 |
0.34 |
0.28 |
0.21 |
| RGP-224-10 |
0.53 GPH |
0.43 |
0.34 |
0.28 |
0.21 |
| RGP 412-01 |
1.02 GPH |
1.64 |
1.31 |
1.09 |
0.82 |
| RGP 412-03 |
1.02 GPH |
1.64 |
1.31 |
1.09 |
0.82 |
| RGP 412-10 |
1.02 GPH |
1.64 |
1.31 |
1.09 |
0.82 |
| RGP 418-01 |
1.02 GPH |
1.09 |
0.87 |
0.73 |
0.55 |
| RGP 418-03 |
1.02 GPH |
1.09 |
0.87 |
0.73 |
0.55 |
| RGP 418-10 |
1.02 GPH |
1.09 |
0.87 |
0.73 |
0.55 |
| RGP-424-03 |
1.02 GPH |
0.82 |
0.65 |
0.55 |
0.41 |
| RGP-424-10 |
1.02 GPH |
0.82 |
0.65 |
0.55 |
0.41 |
| Non-Pressure-Comp. |
RGN 212-05 |
0.62 GPH |
1.00 |
0.80 |
0.66 |
0.50 |
| RGN 218-05 |
0.62 GPH |
0.66 |
0.53 |
0.44 |
0.33 |
| RGN 412-05 |
1.08 GPH |
1.73 |
1.39 |
1.16 |
0.87 |
| RGN 418-08 |
1.08 GPH |
1.16 |
0.92 |
0.77 |
0.58 |
| Microline |
MCRG-206 |
0.62 GPH |
3.98 |
1.99 |
1.33 |
1.00 |
| MCRG-212 |
0.62 GPH |
1.99 |
1.00 |
0.66 |
0.50 |
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Zone Run Time Scheduling Worksheet
To determine zone run times, obtain the
following information:
n monthly evapotranspiration value for the location
n irrigation application rate
(For regional ET data, refer to the Toro Rainfall and
Evapotranspiration
Data Book, Form No. 490-1358.)
The following formulae can be used to
determine run times.
| Run time
per week |
= |
Weekly
evapotranspiration rate |
| Application
rate |
| Run time
per day |
= |
Run
time per week |
| Days per
week |
TABLE 3.2
| MONTH: |
| ZONES |
| DAY |
1 |
2 |
3 |
4 |
5 |
6 |
| Sun. |
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| Mon. |
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| Tues. |
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| Wed. |
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| Thurs. |
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| Fri. |
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| Sat. |
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| * The number of zones may vary depending on the
specific needs of each installation. |
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