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DRIP IRRIGATION MANAGEMENT AND OPERATION
Steps to follow in setting the injection duration and timing
EXAMPLE
A. Calculate the amount of the pure element. Example: Nitrogen
• Quantity of pure nitrogen per month:
50 Kg per hectare.
• Total days in the month:
30 days.
• Quantity of pure nitrogen per day:
50/30 = 1.66 Kg/ha/day
B. Calculate how many liters of liquid fertilizer will be needed
• For 100 liters of final mixture (water and fertilizer) 20 Kg of urea or ammonium nitrate equivalent,
27.8 Kg are dissolved.
• That amount of urea or ammonium nitrate represents 9 Kg of pure nitrogen
(20 Kg * 45%, or 27.8 * 33%).
• If in 100 liters of liquid fertilizer there are 9 Kg of pure nitrogen, it follows that 1 (one) Kg of pure
nitrogen equals 11.1 liters of the mixture (100/9 = 11.1).
• Size of the plot to be irrigated: 20 hectares.
• Total injected liquid fertilizer every day will be:
Total hectares * Kg of pure nitrogen in irrigation * liters of fertilizer per Kg of pure nitrogen =
20 ha * 1.66 kg N per irrigation * 11.1 liters = 368 liters of fertilizer per irrigation.
• Irrigated every two days; therefore 736 liters (368 * 2) must be applied.
C. Required duration of irrigation
• Calculated hourly irrigation capacity of the system:
• The dripper flow is 0.8 liters per hour.
• The distance between drippers is 0.50 meters.
• The distance between the dripperlines is 1.60 meters.
• The hourly capacity irrigation is = 0.8 / (0.5 * 1.6) = 1.0 mm per hour or 10.0 m3 per hectare per hour.
• Daily evaporation tank as Class "A" is 8 mm.
• Replacement coefficient (Kc) = 0.8
• Amount of water to irrigate per day = 8 mm x 0.8 = 6.4 mm or 64 m3 per hectare.
• Run time per day = Total water to irrigate in mm / irrigation Hourly capacity in mm / hour =
6.4 mm / 1.0 mm per hour = 6 hours 24 minutes.
• However, as it is irrigated every other day, irrigate duration should be set for 12 hours and 48 minutes.
D. Required injection time
• In this example, the fertilizer injector is capable of injecting 100 liters per hour.
• Total fertilizer to be injected is 736 liters (step B).
• Time to be injected: 736 liters fertilizer / 100 liters per hour = 7.36 hours (7 hours and 22 minutes).
E. Injection program
Having calculated all the above data, the next step is to decide the timing of fertilizer injection during
irrigation.
Proposed program:
Nutrigation™ = 7:22 hrs
Activity
Irrigation = 13 hrs
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60 DRIP IRRIGATION HANDBOOK
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