Determine water deficit for crops. Balance rainfall with crop needs to optimize irrigation schedules.

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Irrigation Requirement Calculator

How it Works

The calculation subtracts the effective rainfall from the crop water requirement. Formula: $Irrigation Need = Crop Requirement - Effective Rainfall$. If the requirement is 50mm and rainfall is 20mm, the irrigation system must supply the remaining 30mm. Advanced users should account for system efficiency (e.g., drip irrigation is 90% efficient, while sprinklers may be 75%).

What is Irrigation Requirement Calculator?

The Irrigation Requirement Calculator allows farmers and gardeners to manage water resources efficiently by calculating the 'water deficit'. It compares the specific water needs of a crop (based on growth stage and evapotranspiration) against natural precipitation. Over-watering wastes resources and leaches nutrients, while under-watering stunts growth.

Step-by-Step Guide

  • Assess Requirement – Input the water needs of your crop for the current period (in mm or inches).
  • Measure Rainfall – Enter the amount of rain received or forecast.
  • Calculate Deficit – The tool subtracts rain from need to show the gap.
  • Apply Efficiency – Adjust the target volume based on your irrigation method's loss factor.

Example

Input: Need 50mm, Rain 20mm

Result: Irrigate 30mm

FAQ

What is effective rainfall?

Not all rain reaches the roots; some evaporates or runs off. Effective rainfall estimates the usable portion.

Does soil type matter?

Yes. Sandy soil drains fast (needs frequent, small amounts), clay holds water (needs infrequent, deep watering).

How to convert mm to liters?

1 mm of water on 1 square meter = 1 Liter.

Evapotranspiration (ET)?

The combined water loss from soil evaporation and plant transpiration. High heat/wind increases ET.

Drip vs Sprinkler?

Drip is more efficient. If using sprinklers, increase the calculated amount by ~20% to account for evaporation.

Conclusion

Water is a finite resource. Smart irrigation management not only conserves water but also maximizes yield by preventing water stress. Use this tool weekly to adjust your watering schedule based on actual weather conditions rather than a fixed calendar.

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References & Standards

This calculator uses formulas and data standards from Standard References to ensure accuracy.

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