Best Management Practices for Applying Fungicides through Irrigation Equipment

More and more growers with irrigation systems are shifting to chemigation (the application of an approved agrochemical with the irrigation water applied by a center pivot.¹ Though growers often focus on fertigation, the opportunity for a timely fungicide application should also be considered.

There are PROS and CONS to chemigation.²

PROS

• Uniformity of application for best coverage and distribution.
• Targeted/flexible applications.
• Save time and labor.
• Reduced compaction from ground equipment.
• Operator safety – reduced exposure to the applicator.

CONS

• Application is only as uniform as the irrigation system output.
• Need additional investments in equipment to meet state law and safety requirements (see Chemigation Equipment Requirements below).
• Increased wear and tear on the irrigation equipment.
• Risk of water source contamination.
• Skill and knowledge for calibrations.

Chemigation Equipment Safety Requirements³

1. An anti-siphon device on the main water line.
2. A backflow device in the chemical line.
3. A pressure sensor on the pressurized water line.
4. An inspection port (to check the operation of the check valve).
5. An injection port downstream from the anti-siphon device.
6. A chemical resistant injection pump.
7. Interlock between the water pump and the injection pump.

Once irrigation systems are set up to meet safety needs, there are some additional considerations when applying a fungicide for optimal benefits. The application needs to focus on uniform application and coverage of the fungicide rather than water needs.

Best Management Practices for Fungicide Applications through Irrigation Systems:

• Ensure fungicide is registered for pivot use.
• Follow fungicide label regulations and guidelines.
• Top nozzle systems are best for optimal coverage as any plant part above the nozzle will not be treated.
• Ideally, keep the water under 0.25 inches/acre and run the pivot a little slower for optimal plant coverage.
• Follow label recommendations for mixing, surfactant, and agitation needs.
• Calibrate and measure twice!

Cathy Soanes
Channel Agronomist

Sources:

¹Center pivots: Chemigation and fertigation. http://www.traxco.com/chemigation-and-fertigation

²Yost, M., Cardon, G., Allen, N., Sorensen, B., Egbert, K., Creech, E., Ransom, C., and Ramirez, R. 2022. Chemigation guide. Utah State University Extension. https://extension.usu.edu/crops/research/chemigation-guide.pdf

³Chemigation. Irrigation. NDSU Water News. North Dakota State University.

Web sites verified 9/19/23. 1110_292101