Variable-Rate Chemigation via Center Pivots

Tsz Him Lo, Daran R. Rudnick, Tim M. Shaver

Research output: Contribution to journalArticlepeer-review


Center pivots can be used to achieve variable-rate chemigation - applying spatially variable dosages of agricultural chemicals within the same field. This paper first presents equations specifying how a center pivot and the associated chemical injection pump can be operated to vary chemical dosages among sectors of a circle or among arc-shaped zones. This paper then introduces a software tool that facilitates computations for variable-rate chemigation. This paper finally documents two field tests of commercial, uncustomized variable rate chemigation systems. In the catch can test, mean absolute relative error in zone-average adjusted chemical dosage was 17%. In the flow-proportional chemical injection test, the system chemical concentration remained within 5% of the average value despite a fivefold range in water flow rates. With rising popularity of variable-rate application and increasing development of variable-rate chemigation equipment, the time is ripe for applied research and extension of variable-rate chemigation via center pivots.

Original languageEnglish (US)
Article number04019012
JournalJournal of Irrigation and Drainage Engineering - ASCE
Issue number7
StatePublished - Jul 1 2019


  • Center pivot
  • Chemigation
  • Fertigation
  • Site-specific
  • Variable rate

ASJC Scopus subject areas

  • Civil and Structural Engineering
  • Water Science and Technology
  • Agricultural and Biological Sciences (miscellaneous)


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