ANR-925 Calibrating Traveling Guns For Slurry Irrigation
ANR-925, Revised November 1995.
Prepared by Ted W. Tyson, Extension
Agricultural Engineer, Associate Professor, Agricultural Enginnering;
and Perry L. Oakes, State Conservation Engineer, Natural Resources
Conservation Service. Adapted from: Karl VanDevender, Phil Tacker,
and John Langston, Extension Agricultural Engineers; and Angela
Rieck, Assistant Specialist Waste Management. "Calibrating
Traveling Big Gun Sprinklers For Manure Applications," FSA
1022-4M-93-S459. University of Arkansas Cooperative Extension
Service, Little Rock, AK.
Calibrating Traveling Guns For Slurry Irrigation
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Waste storage ponds are used on many dairy, swine, and poultry
layer farms in Alabama as part of the waste management system.
These ponds collect and hold animal waste generated at these operations.
Most waste storage ponds are designed to fill up and be emptied
at least twice and in some cases three times a year. If waste
storage ponds fill up and overflow, they will pollute water sources.
On the other hand, if storage pond slurry is applied to cropland,
it can be an effective part of the waste management plan.
Calibration Procedure
The following example illustrates the calibration procedure
for traveling guns. It applies to both waste slurry and wastewater
irrigation using traveling guns.
|
|
1) Choose nutrient application rate based on the crop grown,
soil characteristics, and the existing nutrient level.
| Example: |
150 lb. N/acre |
| Your numbers: |
_____ lb. N/acre |
|
|
2) Determine waste slurry application rate in gallons per
acre (gal./acre). Divide the nutrient application rate from Step
1 by the pounds of plant-available nutrient per thousand gallons
of slurry (determined by actual test or by site or operation-type
history); then multiply by 1,000.
| Example: |
(150 lb./acre) / (17 lb. N/1,000
gal.) X (1,000) = 8,823 gal./acre |
| Your numbers: |
(___lb./acre) / (__lb.N/1,000 gal.) X (1,000)
= _____ gal./acre |
|
|
3) Determine in./acre of slurry to apply. Divide gal./acre
from Step 2 by 27,154 gal./acre-in.
| Example: |
(8,823 gal./acre) / (27,154 gal./acre-in.)
= .32 in. |
| Your numbers: |
(____ gal./acre) / (_____gal./acre-in.) =
___in. |
|
|
4) From Table 1, select diameter of throw
for existing nozzle size, expected psi, and GPM.* Multiply
by 0.7 for correct travel lane spacing.**
| Example: |
1.0-in. nozzle at 60 psi, 225
GPM,
Lane spacing = (0.7) X (325-ft. diameter of throw) = (227 ft.) |
| Your numbers: |
__-in. nozzle at __ psi, ___ GPM,
Lane spacing = (0.7) X (___-ft. diameter of throw) = (___ ft.) |
|
|
5) Calculate travel speed*** (ft./min.) required. Multiply
1.6 times GPM. Divide by lane spacing (ft.); then divide by inches
applied.
| Example: |
Travel speed = (1.6) X (225 GPM)
/ (227-ft. lane spacing) / (0.32 in.) = 4.95 ft./min. |
| Your numbers: |
Travel speed = (1.6) X (___GPM) / (___-ft.
lane spacing) / (__ in.) = ____ft./min. |
|
|
*Gallons per minute flow rate (GPM)
from any particular nozzle can easily be determined by pressure
at the nozzle. Most traveling guns are equipped by the manufacturer
with a 1/4-inch nipple tap located on the gun body. A presure
gauge can easily be attached at this location and used to check
gun nozzle operating pressure. Table 1 gives
typical flow rates and expected diameters of throw (24 degree
gun trajectory angle) for various size taper bore nozzles used
in traveling guns. This chart can be used to determine traveling
gun flow rate at actual operating pressure if a manufacturer's
chart is not available.
**Travel lane spacing should be 70
percent (0.7) of the nozzle throw diameter for uniform wastewater
application. See Figure 1 for a typical traveling
gun layout.
***Travel speed of the gun cart is
the most complicated of the traveling gun application rate factors
to calculate. Travel speed can be calculated from mathematical
formula, from information in Table 2, or from
a manufacturer's data on particular travel guns.
|
Land application of storage pond slurry with ssprinkler irrigation
equipment is becoming more common in Alabama. This is a good management
practice for two reasons: it allows recycling of on-farm nutrients,
and it reduces the pollution of the surrounding environment.
Land application should match the fertilizer content of slurry
to the crop requirements and soil characteristics. Fertilizer
concentrations in animal waste slurry are quite high, ranging
from more than 500 pounds of total nitrogen per acre inch for
dairy slurry to more than 800 pounds of total nitrogen per acre
inch for swine slurry. Poultry layer slurry may contain twice
these levels of total nitrogen per acre inch. When irrigation
applied, less than half of the total nitrogen is plant available.
Controlling the application depth of animal waste slurry irrigation
is essential to manage off-farm pollution and receive maximum
available benefits from fertilizer in the slurry.
To control the amount of slurry and nutrients being applied
to a field, the operator must properly calibrate slurry irrigation
equipment. Calibrating fertilizer application equipment is not
new to farmers, but calibrating irrigation equipment may be a
relatively new procedure for those unfamiliar with irrigation.
Traveling irrigation guns are commonly used for waste slurry application
and are the most difficult type of irrigation system to calibrate.
Table 1. Typical Nozzle Flow Rates And Diameters
Of Throw For 2-Inch Taper Bore Nozzle With 24 Degree Trajectory.
|
PSI |
Nozzle
0.7" |
Nozzle
0.8" |
Nozzle
0.9" |
Nozzle
1.0" |
Nozzle
1.1" |
Nozzle
1.2" |
Nozzle
1.3" |
| GPM |
DIA |
GPM |
DIA |
GPM |
DIA |
GPM |
DIA |
GPM |
DIA |
GPM |
DIA |
GPM |
DIA |
| 50 |
100 |
250' |
130 |
270' |
165 |
290' |
205 |
310' |
255 |
330' |
300 |
345' |
350 |
360' |
| 60 |
110 |
265' |
143 |
285' |
182 |
305' |
225 |
325' |
275 |
345' |
330 |
365' |
385 |
380' |
| 70 |
120 |
280' |
155 |
300' |
197 |
320' |
245 |
340' |
295 |
360' |
355 |
380' |
415 |
395' |
| 80 |
128 |
290' |
165 |
310' |
210 |
335' |
260 |
355' |
315 |
375' |
380 |
395' |
445 |
410' |
| 90 |
135 |
300' |
175 |
320' |
223 |
345' |
275 |
365' |
335 |
390' |
405 |
410' |
475 |
425' |
| 100 |
143 |
310' |
185 |
330' |
235 |
355' |
290 |
375' |
355 |
400' |
425 |
420' |
500 |
440' |
| 110 |
150 |
320' |
195 |
340' |
247 |
365' |
305 |
385' |
370 |
410' |
445 |
430' |
525 |
450' |
| 120 |
157 |
330' |
204 |
350' |
258 |
375' |
320 |
395' |
385 |
420' |
465 |
440' |
545 |
460' |
 |
Adjusting Gun Cart Speed
After determining travel speed required, either from the chart
or by mathematical calculation, adjust gun cart speed in the
field to this desired speed. Since travel speed is so critical
for slurry and wastewater irrigation, use only those traveling
guns with easily adjustable speed control and speed compensation.
Traveling guns with knob adjustments for a dial readout and with
mechanical linkage speed compensation seem to be the most reliable.
|
Table 2. Wastewater Applied by Traveling Gun Sprinklers.*
| Sprinkler Flow Rate
(GPM) |
Travel Lane Spacing
(ft.)** |
Travel Speed (ft./min.) |
| 0.4 |
0.5 |
1 |
2 |
4 |
6 |
8 |
10 |
| Wastewater Applied
(in.) |
| 100 |
150
200
250
300 |
2.7
2.0
1.6
1.3 |
2.1
1.6
1.3
1.1 |
1.1
0.8
0.6
0.5 |
0.5
0.4
0.3
0.3 |
0.3
0.2
0.2
0.1 |
0.2
0.1
0.1
0.1 |
0.1
0.1
0.1
0.1 |
0.1
0.1
0.1
0.1 |
| 200 |
150
200
250
300 |
5.4
4.0
3.2
2.7 |
4.3
3.2
2.6
2.1 |
2.1
1.6
1.3
1.1 |
1.1
0.8
0.6
0.5 |
0.5
0.4
0.3
0.3 |
0.4
0.3
0.2
0.2 |
0.3
0.2
0.2
0.1 |
0.2
0.2
0.1
0.1 |
| 300 |
200
250
300
350 |
6.0
4.8
4.0
3.4 |
4.8
3.9
3.2
2.8 |
2.4
1.9
1.6
1.4 |
1.2
1.0
0.8
0.7 |
0.6
0.5
0.4
0.3 |
0.4
0.3
0.3
0.2 |
0.3
0.2
0.2
0.2 |
0.2
0.2
0.2
0.1 |
| 400 |
200
250
300
350 |
8.0
6.4
5.4
4.6 |
6.4
5.1
4.3
3.7 |
3.2
2.6
2.1
1.8 |
1.6
1.3
1.1
0.9 |
0.8
0.6
0.5
0.5 |
0.5
0.4
0.4
0.3 |
0.4
0.3
0.3
0.2 |
0.3
0.3
0.2
0.2 |
| 500 |
250
300
350
400 |
8.0
6.7
5.7
5.0 |
6.4
5.4
4.6
4.0 |
3.2
2.7
2.3
2.0 |
1.6
1.3
1.1
1.0 |
0.8
0.7
0.6
0.5 |
0.5
0.4
0.4
0.3 |
0.4
0.3
0.3
0.3 |
0.3
0.3
0.2
0.2 |
| 600 |
250
300
350
400 |
9.6
8.0
6.9
6.0 |
7.7
6.4
5.5
4.8 |
3.9
3.2
2.8
2.4 |
1.9
1.6
1.4
1.2 |
1.0
0.8
0.7
0.6 |
0.6
0.5
0.5
0.4 |
0.5
0.4
0.3
0.3 |
0.4
0.3
0.3
0.2 |
| 700 |
300
350
400
450 |
9.4
8.0
7.0
6.2 |
7.5
6.4
5.6
5.0 |
3.7
3.2
2.8
2.5 |
1.9
1.6
1.4
1.2 |
0.9
0.8
0.7
0.6 |
0.6
0.5
0.5
0.4 |
0.5
0.4
0.4
0.3 |
0.4
0.3
0.3
0.2 |
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* If your exact numbers are not in the table,
use the formula below to calculate the application rate. The
mathematical operations should be done in order from left to
right. Wastewater applied (in.) = (1.6) X (sprinkler flow rate
(GPM)) / (lane spacing (ft.)) / (speed (ft./min.))
** The travel lane spacing should be approximately
70 percent of the sprinkler's coverage diameter. The coverage
diameter can be determined from the manufacturer's literature
or by measurement. Refer to Figure 1 for a diagram of a traveling
fun layout.
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Checking Gun Cart Speed
Checking actual traveling gun cart speed is a simple matter.
You'll need two flags, a 100-foot tape, and a wristwatch with
a minute and second indicator. Set up the gun, and extend the
hose. Then:
1) Measure off a 100-foot distance along the gun cart travel
path and mark with the flags.
2) Use a marker, ribbon, or string to mark a point on the retracting
hose or cable that is pulling the gun cart.
3) During traveling gun irrigation operation, measure and record
the time in minutes and seconds required by the ribbon to travel
the measured 100-foot distance.
4) Convert travel time in minutes and seconds to minutes and
partial minutes (minutes and seconds = whole minutes + seconds/60).
Example: 1 minute, 27 seconds = 1 + 27/60 = 1 + 0.45 =
1.45 minutes
5) Divide the travel distance (100 feet) by the travel time
in minutes to get travel speed in feet per minute. After determining
the travel speed, adjust the speed control as necessary to get
the desired travel speed.
For more information, call your
county Extension office. Look in your telephone directory under
your county's name to find the number.
For more information, contact your county Extension office. Visit http://www.aces.edu/counties or look in your telephone directory under your county's name to find contact information.
Issued in furtherance of Cooperative Extension work in agriculture and
home economics, Acts of May 8 and June 30, 1914, and other related
acts, in cooperation with the U.S. Department of Agriculture. The Alabama
Cooperative Extension System (Alabama A&M University and Auburn
University) offers educational programs, materials, and equal
opportunity employment to all people without regard to race, color,
national origin, religion, sex, age, veteran status, or disability.
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