1. What is Irrigation Water Need?

The irrigation water need (IN) is the amount of water required to supplement natural precipitation to meet crop water requirements. It's calculated as the difference between evapotranspiration (ET) and effective precipitation (Pe).

2. How Does the Calculator Work?

The calculator uses the basic irrigation need equation:

Where:

• \( IN \) — Irrigation need (mm)
• \( ET \) — Evapotranspiration (mm)
• \( Pe \) — Effective precipitation (mm)

Explanation: The equation accounts for the water lost through evapotranspiration and subtracts the water gained from effective precipitation.

3. Importance of Irrigation Calculation

Details: Accurate irrigation need calculation is crucial for efficient water use, preventing over-irrigation (which can lead to waterlogging and nutrient leaching) and under-irrigation (which can stress crops).

4. Using the Calculator

Tips: Enter evapotranspiration and effective precipitation in millimeters. Both values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is effective precipitation?
A: Effective precipitation is the portion of total rainfall that is available to plants after accounting for runoff and deep percolation.

Q2: How do I measure evapotranspiration?
A: ET can be measured using weather station data, lysimeters, or calculated using reference ET and crop coefficients.

Q3: What factors affect irrigation needs?
A: Crop type, growth stage, soil type, climate conditions, and irrigation efficiency all affect water needs.

Q4: Are there limitations to this simple equation?
A: This basic equation doesn't account for soil water storage, irrigation efficiency, or crop coefficients which may be important for precise calculations.

Q5: How often should I calculate irrigation needs?
A: For most crops, weekly calculations are sufficient, though daily calculations may be needed for sensitive crops or in extreme weather.