Certified Landscape Irrigation Auditor

To calculate turf irrigation needs, ET from reference crops should be decreased by what percentage?

1. 10 - 15%

2. 15 - 20%

3. 20 - 30%

4. 30 - 40%

The correct answer is: 20 - 30%

The calculation of turf irrigation needs often begins with estimating evapotranspiration (ET) from reference crops, which typically have a different water requirement than turfgrass. In practical applications, environmental factors such as the type of turf, microclimates, and varying moisture retention in the soil must be considered. To effectively adjust the reference ET values to meet the specific irrigation needs of turf, it is generally necessary to decrease the reference ET by 20 to 30%. This range is recognized because turfgrass typically uses less water than many reference crops, and this adjustment accounts for factors like lower leaf area and different rooting depths. By reducing the ET values in this manner, irrigation systems can be optimized to provide sufficient water without over-irrigating, which would not only be wasteful but could also lead to runoff and other irrigation-related issues. Implementing this percentage provides a guideline that reflects proper water management practices while ensuring that the turf receives adequate moisture for healthy growth.