Water is one of the most valuable resources in agriculture. Too little water reduces crop yield, while too much water wastes resources and harms soil health. Knowing how much water a crop actually needs is essential for efficient farming.
This article explains irrigation water requirement calculation in simple words, without complex formulas.
What Is Irrigation Water Requirement?
Irrigation water requirement means the amount of water that must be supplied to a crop through irrigation to meet its needs when rainfall is not enough.
In simple terms:
It is the water required by the crop minus the water received from rainfall.
Why Calculating Water Requirement Is Important
Correct irrigation calculation helps farmers to:
- Save water
- Reduce electricity and pumping costs
- Prevent waterlogging and root damage
- Improve crop growth and yield
- Practice sustainable farming
Main Factors That Decide Crop Water Requirement
1. Crop Type
Different crops need different amounts of water.
- Rice needs more water
- Pulses and millets need less water
2. Crop Growth Stage
Water requirement changes with crop stage:
- Early stage → low water
- Flowering and grain filling → high water
3. Soil Type
- Sandy soil → holds less water, needs frequent irrigation
- Clay soil → holds more water, needs less frequent irrigation
4. Climate
- Hot and dry weather → more water needed
- Cool and humid weather → less water needed
5. Rainfall
Effective rainfall reduces irrigation requirement.
Simple Method to Calculate Irrigation Water Requirement
Step 1: Know Crop Water Need
Crop water requirement is usually given in millimeters (mm) for the entire growing season or for a specific period.
Example:
- Crop water requirement = 500 mm
Step 2: Know Effective Rainfall
Rainfall that actually helps the crop.
Example:
- Effective rainfall = 150 mm
Step 3: Calculate Irrigation Water Requirement
Simple Formula
Irrigation Water Requirement = Crop Water Requirement – Effective Rainfall
Example Calculation
500 mm – 150 mm = 350 mm
So, the crop needs 350 mm of irrigation water.
How to Convert Water Depth into Volume
Farmers often want water in volume, not mm.
Simple Rule
1 mm water over 1 hectare = 10,000 liters
Example
350 mm × 10,000 = 3,500,000 liters per hectareIrrigation Water Requirement per Acre
1 hectare = 2.47 acres
3,500,000 ÷ 2.47 ≈ 1,417,000 liters per acreIrrigation Requirement Depends on Irrigation Method
| Method | Water Use |
|---|---|
| Flood irrigation | High |
| Furrow irrigation | Medium |
| Drip irrigation | Low |
| Sprinkler irrigation | Medium to low |
Efficient methods like drip irrigation reduce water requirement significantly.
Common Mistakes Farmers Make
- Irrigating without knowing crop need
- Applying same water quantity at all stages
- Ignoring rainfall contribution
- Over-irrigation leading to nutrient loss
How Agro Life Calculator Makes This Easy
Agro Life Calculator helps farmers:
- Calculate crop water requirement instantly
- Convert mm to liters automatically
- Adjust for area and irrigation method
- Avoid manual calculation errors
Conclusion
Calculating irrigation water requirement is not difficult. By understanding crop needs, rainfall, soil, and climate, farmers can apply the right amount of water at the right time.
Using tools like Agro Life Calculator makes irrigation planning simple, accurate, and efficient, leading to better yields and water savings.