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Understanding leaching fraction testing: a beginner's guide

Leaching fraction is the simplest measure of whether you are overwatering. Here is how to run the test with a scale, a clipboard, and a sleeve pot.

Caleb Saunders Co-founder, Canopy
2 min read
Three people in a hoop house weighing and inspecting container plants, one recording on a phone

Leaching fraction testing is a crucial best management practice in the container nursery industry, helping optimize irrigation efficiency. This guide walks you through the steps to perform this test effectively.

What is a leaching fraction?

Leaching fraction is the amount of water that drains out of a container after irrigation, divided by the amount of irrigation water applied. It tells you how efficient your irrigation is.

Taking a leaching fraction measurement is quite easy with a scale, a clipboard, and a sleeve pot, as the photo above shows. The specific steps are below.

Steps for conducting a leaching fraction test

1. Preparation

  • Select 3 to 5 random plants from your overhead or sprinkler-irrigated area.
  • Just before their scheduled irrigation, weigh each plant and its container.

2. Initial weighing

  • Place each plant in an identical, empty container without holes.
  • Record the weight of each plant and container.

3. Irrigation

  • Return the plants to their positions and irrigate as usual.
  • After irrigation, weigh and record the plants again.

4. Collecting leachate

  • Allow the excess water (leachate) to drain into the containers without holes.
  • Weigh and record the containers with leachate.

5. Calculations

  • Subtract the initial container weight from the post-irrigation weight to find the amount of leachate.
  • Calculate the leaching fraction:

Best practices

  • Aim for a leaching fraction of 10 to 15%.
  • Adjust irrigation based on the results: increase if the fraction is low, and decrease if it is high.

Conclusion

Regular leaching fraction testing can significantly enhance your irrigation practices, leading to better water management and healthier plants. Conduct these tests periodically and adjust your irrigation schedules accordingly to maintain optimal plant growth and resource use.

Special thanks

Thanks to the contributors to this post including Tom Yeager and Jeff Million.

Sources:

  • Million and Yeager 2024. Jeff Million and Tom Yeager, UF IFAS Extension Publication #ENH1268 May 21, 2024. Monitoring Leaching Fraction for Irrigation Scheduling in Container Nurseries. https://edis.ifas.ufl.edu/publication/EP529