The document discusses fertigation, which is the process of applying fertilizers through irrigation systems. It covers the need for fertigation to address issues like soil fertility depletion. Key topics include characteristics of fertilizers suitable for fertigation like solubility, compatibility between fertilizers, and common fertigation equipment like fertilizer tanks, venturi injectors, and injection pumps. The document provides guidance on calculating fertilizer requirements and examples for determining the needed quantities based on recommended doses.

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Integrated Rural and Agricultural Development
Association (IRADA), Satara
Online Training on
“Advanced Irrigation and Precision Agriculture”
Use of Various Fertigation Devices
By
Er. A. A. Shelke
Ph.D. Scholar (Irrigation & Drainage Engineering)

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Contents
• Need of ferigation
• Fertigation concept
• Characteristics and compatibility of fertilizers
• Fertigation Equipments

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If you take care of
your soil, the soil will
take care of your plants.
water, 25
air, 25
organic
matter, 5
mineral
matter, 45
The ideal soil must consist 50% pore space and
50 % solids

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Need of Fertigation
• Uneven growth in fertilizer consumption resulting in state wise crop
wise variation in consumption.
• Mining of nutrients from soil at alarming rates (soil fertility
depletion due to inadequate and imbalanced fertilizer use.)
• Decline in crop response to fertilizer
• Stagnation in fertilizer production
• Weakening relationship between fertilizer use and food grain
production
• Increasing dependence on fertilizer imports

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What is Fertigation?
• Fertilizer + Irrigation = Fertigation
• Nutrient “spoon feeding”
• Can be done by:
– hand
– sprinkler system
– drip irrigation system

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Distribution of plants nutrients

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Advantages of fertigation
• Increase in yield by 25 to 30 %
• Saving in fertilizer by 25 to 30 %
• Precise application and uniform distribution of fertilizers
• Nutrients can be applied as per plant requirement
• Acidic nature helps in avoiding clogging of drippers
• Minimizing nutrient losses
• Major and minor nutrients can be applied in one solution with
irrigation
• Fertilizers can be applied as per required concentration
• Saving in time, labour and energy
• Light soils can be brought under cultivation

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Characteristics of fertilizers suitable for
fertigation
• High nutrient content readily available to plants
• Fully water soluble at filed temperature conditions
• Fast dissolution in irrigation water
• No clogging of filters and emitters
• Low content of insolubles (less than 0.02 %)
• Minimum contents of conditioning agents
• Competible with other fertilizers
• Minimal interaction with irrigation water
• No drastic change in water pH (3.5< pH>9.0)
• Low corrosive for control head and system

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Solubility of fertilizers
• The quantity of fertilizer that can be dissolved in unit quantity
of water is called fertilizer solubility
• Solubility of fertilizer is affected by temperature vatiations

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Types of fertilizers
a) Nitrogenous Fertilizers
these fertilizers are most commercially available and
readily soluble in water and hence treating as good fertigating
agents.
Solubility of nitrogenous fertilizers
Type of fertilizer Nitrogen content
(%)
Solubility
(gm/litre)
Ammonium
sulphate
21 750
Urea 46 1100
Ammonium nitrate 34 1920
Calcium nitrate 15.5 1290

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Characteristic Of Nitrogenous Fertilizer
Suitable For Fertigation
Fertilizer Grade Formula pH (1 g/L at 20°C )
Urea 46-0-0 CO(NH2) 2 5.8
Potassium Nitrate 13-0-46 KNO3 7.0
Only Fertigation Grade
Ammonium Sulphate 21-0-0 (NH4)2SO4 5.5
Urea Ammonium Nitrate 32-0-0 CO(NH2)2. NH4 NO3 5.5
Ammonium Nitrate 34-0-0 NH4 NO3 5.7
Mono Ammonium
Phosphate (MAP)
12-61-0 NH4 H2PO4 4.9
Calcium Nitrate 15-0-0 Ca(NH3)2 5.8
Magnesium Nitrate 11-0-0 Mg(NH3)2 5.4s

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b) Potassic fertilizers
these are best suited for fertigation.
Solubility of potassic fertilizers
Type of fertilizer Potassium content (%) Solubility (gm/litre)
Potassium sulphate 50 110
Potassium chloride 60 340
Potassium nitrate 44 133

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Characteristic Of potassic Fertilizer Suitable For
Fertigation
Fertilizers Grade Formula pH Other nutrients
Potassium chloride@ 0-0-60 KCl 7.0 46% Cl
Potassium Nitrate 13-0-46 KNO3 7.0 13% N
Potassium Sulphate# 0-0-50 K2SO4 3.7 18% S
Potassium
Thiosulphate*
0-0-25 K2S2O3 - 17% S
Mono Potassium
Phosphate
0-52-34 KH2PO4 5.5 52% P2O5
@: Only white, #: Only fertigation grade, *: Liquid

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c) Phosphatic Fertilizers
• P+ Ca = Calcium Phosphate (insoluble)
• P+ Ammonium + Magnesium = magnesium ammonium
phosphate (insoluble)
• P + iron = Iron Phosphate (insoluble)
• Even good P sources like poly phosphates gets precipitated if
Ca + Mg in water is > 50ppm and bicarbonate > 150 ppm.
• If bicarbonate content is < 100 ppm, the Ca + Mg content can
go up to 75 ppm.

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Characteristic Of phosphatic Fertilizer Suitable
For Fertigation
Fertilizer Grade Formula pH(1 g/L at 20°C )
Phosphoric Acid 0-52-0 H3PO4 2.6
Mono Potassium Phosphate 0-52-34 KH2PO4 5.5
Mono Ammonium
Phosphate
12-61-0 NH4 H2PO4 4.9

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d) Micro nutrients
Elements which are required for plant growth which are
required in small amounts less than primary nutrients such as N,
P and K.
Solubility of Micro nutrient fertilizers
Fertilizer Content % Solubility ( gm/L )
Solubor 20 B 220
Copper sulphate 25 Cu 320
Iron sulphate 20 Fe 160
Magnesium
Sulphate
10 710
Ammonium
molybdate
54 430
Zinc sulphate 36 965
Magnesium
sulphate
27 1050

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Compatibility of fertilizers
• Mixing the solution of two or more than two water soluble
fertilizers can sometimes results in formation of precipitate.
• To avoid such problems of formation of precipitates, their
solutions should be prepared in two separate tanks.

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Interaction between fertilizers nutrients -
Compatibility
a) Calcium Nitrate with any sulphates = formation of CaSO4 (Gypsum)
precipitate
Ca (NO3)2 + (NH4)2SO4 ◊ CaSO4 ↓+…………
b) Calcium Nitrate with any phosphates = formation of calcium
phosphate precipitate
Ca (NO3)2 + NH4H2PO4 ◊ CaHPO4 ↓+…………
c) Magnesium with mono ammonium phosphate = formation of
magnesium phosphate precipitate
Mg(NO3)2 + (NH4)2 H2PO4 ◊ MgHPO4 ↓+…………
d) Ammonium sulphate with KCl or KNO3 = formation of K2SO4
precipitate
SO4 (NO3)2 + KCl or KNO3 ◊ K2SO4 ↓+…………
e) Phosphorus with iron = Iron phosphate precipitate

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Compatibility chart for different water soluble
fertilizers

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Fertilizer evaluation for suitability to fertigation
Property NH4 NO3 (NH4)2SO4 K2SO4 KCl KNO3 H3PO4 MAP
Solubility High Medium Low Medium Medium High Medium
Precipitation Low High High Low Low Low High
Compatibility Good Poor Poor Medium Medium Medium good
corrosion Medium Poor Poor Poor Good Poor Medium

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Chemical Aspects of Fertigation
• Solubility limits of the least soluble salt in solution.
• Precipitation of Ca-Mg/P compouds:
a) Clogging of drippers and filters
b) Less nutrient availability
• Corrosivity
corrosivity of fertilizers
Kind of metal Ca(NH3)2 (NH4)2SO4 NH4 NO3 Urea H3PO4 DAP
Galvanized
Iron
2 4 4 1 4 1
Sheet
Aluminium
No 1 1 No 2 2
Stainless Steel No No No No 1 No
Bronze 1 3 3 No 2 4
Brass 1 2 3 No 2 4
No = None, 1= Slight, 2 = Moderate, 3 = Considerable, 4 = Severe

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Fertigation Equipments
• Fertilizer tank
• Venturi Injector
• Injection pump

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Fertigation tank
• Mild steel construction
• Powder coated Turbulent inlet
• Separate valves are
• Special provision of strainer on the outlet
• Wide 8”
• Drain port is provided to flush out the tank
• 10 kg/ cm2
• Available in 30,60,90,120 and 160 litres
capacity

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Venturi injector
• Made of engineering plastic.
• chemical resistance
• Highly efficient and compact
differential pressure injection
device.
• Economical and low cost
option.
• Available in ¾”, 1", 1½" and 2"
BSP inlet/outlet connection.

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Fertilizer Injection Pump
• Made of strong plastic material.
• Compact design.
• Accurate.
• operates on hydraulic pressure.
• Dosing rate can be set externally to
desired percentage.
• 5 kg/cm² (70 psi).
• Simple to install, operate and maintain.
• Low pressure loss.
• ¾” BSP inlet/outlet connection .
• Dosing flow range,
- 0.6 to 50 lph for 0.3% to 2% adjustable.
- 0.12 to 100 lph for 0.4% to 4% adjustable.
- 150 lph for 6% fixed dosage.

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Comparative performance of
fertigation equipment's

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Preparing fertilizer stock solutions at
filed conditions

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Points to be remembered while
adopting fertigation
1. Fertilizer tank or injection pump may be used to inject the fertilizers
2. For precise placement of both water and fertilizers, it is necessary to use
pressure compensating drippers or inline drippers instead of micro
tubes.
3. Daily feeding is most desirable, if not possible feed alternate day.
4. Urea can be combined with WSF for meeting the N requirement.
5. fertigation should be done during at the end of irrigation period, run the
drip irrigation system for 5 to 6 minutes after the completion of
fertigation.
6. It is not advisable to use a very concentrated stock solution (not more
than 10%)
7. Do not inject the fertilizers in combination with pesticides or chlorine.
8. The injection point must be upstream of the filter system so that the filer
will remove any un dissolved fertilizers or precipitates that occur.
9. Select the fertilizer solutions which helps to adjust water pH if necessary.

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How to calculate fertilizer requirement
• Fertilizer required =
100
𝑛𝑢𝑡𝑟𝑖𝑒𝑛𝑡 𝑐𝑜𝑛𝑡𝑒𝑛𝑡 %
𝑥 𝑅𝐷𝐹
Fertiizer Nutrient % Factor
Ammonium sulphate 21 N 4.76
Urea 46 N 2.17
Ammonium nitrate 34 N 2.94
Calcium nitrate 15.5 N 6.45
Potassium sulphate 50 K 2
Potassium chloride 60 K 1.67
Potassium nitrate 46 K & 13 N 2.27 & 7.69
Phosphoric Acid 52 P 1.92
Mono Potassium
Phosphate
52 P & 34 K 1.92 &
Mono Ammonium
Phosphate
61 P & 12 N 1.64 & 8.33

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Lets try some examples
Ex. If the recommended dose of fertilizer is 120:60:40 kg/ha N:P:K. calculate the required fertilizers ?
-select urea to fulfil the requirement of N
120 x 2.17 = 260.4 kg of urea
-Select mono potassium phosphate to fulfil requirement of P2O5
60 x 1.92 = 115.2
-Here , mono potassium phosphate also contains 34 % of potassium.
Then 115.2 kg of mono potassium phosphate contains
0.34 x 115.2 = 39.16 kg of K
-So here RDF of 120:60:40 kg/ha of NPK is fulfilled by
Urea = 260.4 Kg
Mono Potassium Phosphate = 115.2 Kg

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Ex. Crop : Sugarcane ,Area : 2 acre
Recommended dose of fertilizer is 150:70:100 kg/ha of N:P:K
Fertilizer Availability : Urea, 19:19:19, SOP
Calculate required quantity of fertilizers to fulfil the nutrient demand
• here area is 2 acres = 4047 x 2 = 8094 sq.m.
• calculation factor for urea =100/46= 2.17
• calculation factor for 19:19:19 = 100/19 = 5.26
Here 19:19:19 complex provides N, P and K
Then,
Calculate the amount of 19:19:19 complex for supplying the P to field
Quantity of P =
𝑹𝑫𝑭×𝑷𝒍𝒐𝒕 𝒂𝒓𝒆𝒂
𝟏𝟎𝟎𝟎𝟎
=
𝟕𝟎×𝟖𝟎𝟗𝟒
𝟏𝟎𝟎𝟎𝟎
= 56.66 kg of P

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Hence , to supply 56.66 kg of P , required amount of 19:19:19 will be
= 56.66 x 5.26 = 298 kg of 19:19:19 complex
Here these 298 kg of 19:19:19 provides =
298 x 0.19 = 56.62 kg of N
Here these 298 kg of 19:19:19 provides =
298 x 0.19 = 56.62 kg of K
Quantity of N for 2 acre =
𝑅𝐷𝐹×𝑃𝑙𝑜𝑡 𝑎𝑟𝑒𝑎
10000
=
𝟏𝟓𝟎×𝟖𝟎𝟗𝟒
𝟏𝟎𝟎𝟎𝟎
= 121.4 Kg of N for 2 Acres
Here to supply 121.4 – 56.62 = 64.78kg of N, the required amount of urea is
= 64.78 x 2.17 =140.57 Kg of urea

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Then,
to supply K we will use SOP having the grade 0-0-50
The quantity of K for 2 acre =
𝑅𝐷𝐹×𝑃𝑙𝑜𝑡 𝑎𝑟𝑒𝑎
10000
=
𝟏𝟎𝟎×𝟖𝟎𝟗𝟒
𝟏𝟎𝟎𝟎𝟎
= 80.94 kg of K
Then we need supply 80.94-56.62
= 24.32 kg of K to fulfil the demand of K
To supply 24.32 kg of K , quantity of SOP needed will be
= 24.32 x 2 = 48.64 kg of SOP

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Thank you