Leaching Fraction Explained
A leaching fraction is simply the amount of water that leaves the container after you run irrigation divided by the total amount of water that was applied and captured by the container during irrigation. The last number is arrived at by subtracting the weight of a dry plant before irrigation from a wet plant after irrigation. This simple equation creates a number, the leaching fraction. When multiplied by 100 will give a percent. The Water Quality/Quantity Best Management Practices for Florida Nurseries manual states that the leaching fraction percent should be 10-15%. If the number is extremely low say 0-5% you may be under-watering plants. If the number is higher than you are over-watering plants. You can easily do this with buckets attached underneath the pots you are growing, randomly scattered in your field. This can be easily done for small annual containers to large containers with a slight modification on catching the leachate. For more information here is a video that can be found in the BMP Manual http://www.freshfromflorida.com/Media/Files/Agricultural-Water-Policy-Files/Best-Management-Practices/Nursery-Videos/Video-8-Leaching-Fraction If you would like to see the rest of the Florida Nursery manual here is a link to that http://www.freshfromflorida.com/content/download/37570/848371/NurseryBMP.pdf If you would like help setting up a leaching fraction and interpreting the results, contact Shawn at UF/IFAS Extension Hillsborough/Polk County firstname.lastname@example.org for a nursery visit.