Monday, April 18, 2011

Sprinkler Spacing and Water Application Uniformity | by Jerry Gerdes

Sprinkler packages designed with proper sprinkler spacing will maintain a high uniformity of water application throughout the field. A number of factors determine the sprinkler spacing. These include sprinkler wetted diameter, operating pressure, ground height, and crop type.

A “rule of thumb” used for correct sprinkler spacing is the water pattern overlap between two adjoining sprinklers must be a minimum of 150% of the sprinkler spacing. A sprinkler placed at a low ground clearance (ex: 36”) to minimize evaporation and wind drift losses for a low-growing crop, such as rice, may require a closer sprinkler spacing compared to the same sprinkler at a higher ground clearance (ex: 108”). If a low ground clearance sprinkler package for rice is also used for a tall crop, such as field corn, the sprinkler spacing must be no more than 60” regardless of the sprinkler model. The tall crop canopy interference will greatly reduce the wetted diameter of any sprinkler model requiring a close spacing.

Valmont Irrigation offers two coupler spacing options for its span pipe:
  1. The standard spacing of 108” works well for applications where the sprinkler ground clearance is at the trussing level or higher.

  2. An optional coupler spacing of 30” is used for applications where the sprinklers are low to the ground and/or within the crop canopy.

Discussion Box Challenge

If you are a center pivot/linear user, what challenges have you experienced with uniformity?

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