David Owens, Extension Entomologist, owensd@udel.edu
One person wrote in a potential cause of last week’s trickle tape woe is red brown algae. Another one, and is the case in this photo, is excessive iron deposits.
A blurb from Weekly Crop Update Volume 31, Issue 13: Drip Irrigation Woes by Gordon Johnson, Retired Extension Specialist; gcjohn@udel.edu :
A common cause of plugged emitters is water containing high levels of dissolved iron. This can cause a proliferation of iron utilizing bacteria. These bacteria form heavy biofilms on the inside of the drip tube. They also oxidize the iron in the water (as part of their metabolism) and leave behind iron precipitates that can plug emitters. Chlorination of drip lines is needed to control iron bacteria. Periodic treatment before clogging develops can keep the system functioning efficiently. The frequency of treatment depends on the quality of the water source. Generally, two or three treatments per season is adequate. Irrigation water containing high concentrations of iron (greater than 1 ppm) can also result in clogging problems due to types of bacteria that “feed” on dissolved (ferrous) iron. The bacteria secrete a slime called ochre that may combine with other solid particles in the trickle tubing and plug emitters. The precipitated (ferric) form of iron, known commonly as rust, can also physically clog emitters. Treating water containing iron with chlorine will oxidize the dissolved iron, causing the element to precipitate so that it can be filtered and removed from the system. Chlorine treatment should take place upstream of filters to remove the precipitated iron and microorganisms from the system. Take care when adding chlorine to trickle irrigation systems, however, since concentration at or above 30 ppm can be toxic to growing plants.
Options for treating water with high iron include the following:
For iron treatment:
- Inject liquid sodium hypochlorite continuously at a rate of 1 ppm for each 1 ppm of iron in irrigation water. In most cases, 3 to 5 ppm is sufficient.
For bacteria treatment:
- Inject liquid sodium hypochlorite continuously at a rate of 5 to 10 ppm where the biological load is high or
- Inject 10 to 20 ppm during the last 30 minutes of each irrigation cycle or
- Inject 50 ppm during the last 30 minutes of irrigation cycles one to two times each month or
- Super chlorinate (inject at a rate of 200 to 500 ppm) once per month for the length of time required to fill the entire system with this solution and shut down the system. After 24 hours, open the laterals and flush the lines.
Irrigation or water treatment companies can also install treatment systems to remove iron from irrigation water. This requires a water test to determine the form of iron and the proper system for its removal.
Read the full article here: https://sites.udel.edu/weeklycropupdate/?p=22675
Check your water quality!!
