Irrigation Requirements of Crops
Understanding Consumptive Irrigation Requirement (CIR), Net Irrigation Requirement (NIR), Field Irrigation Requirement (FIR), and Gross Irrigation Requirement (GIR) in irrigation engineering.
Efficient irrigation management is one of the most important aspects of agricultural engineering and water resource planning. Proper estimation of irrigation requirements helps conserve water, improve crop productivity, and ensure sustainable agriculture.
The irrigation requirement of crops is generally divided into four major stages:
- Consumptive Irrigation Requirement (CIR)
- Net Irrigation Requirement (NIR)
- Field Irrigation Requirement (FIR)
- Gross Irrigation Requirement (GIR)
1. Consumptive Irrigation Requirement (CIR)
Consumptive Irrigation Requirement represents the quantity of water actually consumed by the crop during its growth period.
CIR = Etc − Re
or
CIR = Cu − Re
Where:
- Etc = Crop evapotranspiration
- Cu = Consumptive use
- Re = Effective rainfall
Importance of CIR
- Helps estimate actual crop water demand
- Useful in irrigation scheduling
- Important for reservoir and canal planning
- Improves efficient water management
2. Net Irrigation Requirement (NIR)
Net Irrigation Requirement is the quantity of water required at the crop root zone after considering additional agricultural requirements.
NIR = CIR + LR + PSR + NWR
Where:
- LR = Leaching requirement
- PSR = Presoaking requirement
- NWR = Nursery water requirement
Additional Components
- Leaching removes excess salts from soil
- Presoaking is important for paddy cultivation
- Nursery requirement covers water for seedlings
3. Field Irrigation Requirement (FIR)
Field Irrigation Requirement accounts for water losses occurring during application in the field.
FIR = NIR / na
Where:
- NIR = Net irrigation requirement
- na = Water application efficiency
Typical Application Efficiencies
| Irrigation Method | Efficiency Range |
|---|---|
| Surface Irrigation | 50–70% |
| Sprinkler Irrigation | 70–85% |
| Drip Irrigation | 85–95% |
4. Gross Irrigation Requirement (GIR)
Gross Irrigation Requirement is the total quantity of water required from the source considering conveyance losses.
GIR = FIR / nc
Where:
- FIR = Field irrigation requirement
- nc = Water conveyance efficiency
Typical Conveyance Efficiencies
| Conveyance System | Efficiency Range |
|---|---|
| Earthen Canal | 60–75% |
| Lined Canal | 75–90% |
| Pipeline System | 90–98% |
Factors Affecting Irrigation Requirements
Climate
Temperature, humidity, rainfall, sunshine, and wind influence crop water demand.
Crop Type
Different crops require different quantities of irrigation water.
Soil Properties
Permeability, infiltration rate, and water holding capacity affect irrigation needs.
Irrigation Method
Modern systems like drip irrigation improve efficiency and reduce losses.
Conclusion
The concepts of CIR, NIR, FIR, and GIR are fundamental in irrigation engineering and water resource management. Accurate estimation of irrigation requirements helps maximize agricultural productivity while conserving valuable water resources.
Author
Mohan Dangi (Gold Medalist)
Civil Engineer | Geotechnical Engineer | Content Creator
References
- Punmia, B.C., Lal, A., and Jain, A.K. – Irrigation and Water Power Engineering
- Garg, S.K. – Irrigation Engineering and Hydraulic Structures
- FAO Irrigation and Drainage Papers
- IS Codes related to Irrigation Engineering
- Ministry of Jal Shakti, Government of India
Disclaimer
This article is intended for educational and informational purposes only. The formulas, concepts, and values provided may vary depending on field conditions, crop type, and project requirements. Readers are advised to consult relevant standards and professional guidelines before applying the information in engineering projects.
0 Comments