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United States Department of Agriculture

Agricultural Research Service

Research Project: Soil and Water Conservation for Northwestern Irrigated Agriculture

Location: Northwest Irrigation and Soils Research

Title: Infiltration model for center pivot irrigation on bare soil

Authors
item King, Bradley
item Bjorneberg, David

Research conducted cooperatively with:
item

Submitted to: ASABE Annual International Meeting
Publication Type: Proceedings
Publication Acceptance Date: June 22, 2012
Publication Date: July 29, 2012
Citation: King, B.A., Bjorneberg, D.L. 2012. Infiltration model for center pivot irrigation on bare soil. ASABE Annual International Meeting. July 29 -August 1, 2012, Dallas, TX. Paper No. 12-1336890, p.1-20.

Interpretive Summary: The marked reduction in infiltration rate caused by formation of a soil surface seal due to water droplet impact on bare soil is a well known phenomenon but is rarely considered in infiltration models, especially under center pivot irrigation. The objective of this study was to develop a soil infiltration model for center pivot sprinkler irrigation that incorporates the transient reduction in soil surface seal hydraulic conductivity as affected by soil and sprinkler characteristics. A sealing soil infiltration model was developed using an explicit finite difference solution scheme with a transient soil seal formation model, which is unique from other studies in that it explicitly uses droplet specific power as the driving factor for formation of a soil surface seal. The model was calibrated to four specific soils using published and laboratory runoff data from rainfall simulation studies with varying droplet kinetic energies and application rates. The model was then applied to center pivot irrigation for five common sprinklers to evaluate the effect sprinkler selection has on infiltration. Due to the high susceptibility of the soils to surface sealing from water drop impact, the sprinkler with the largest wetted diameter was predicted to maximize infiltration. If a center pivot sprinkler irrigation system is operated over a bare soil at the application rates used in this study, a surface seal is going to form, and the only way to maximize infiltration depth is to apply the water over the largest time interval possible.

Technical Abstract: The marked reduction in infiltration rate caused by formation of a soil surface seal due to water droplet impact on bare soil is a well known phenomenon but is rarely considered in infiltration models, especially under center pivot irrigation. The objective of this study was to develop a soil infiltration model for center pivot sprinkler irrigation that incorporates the transient reduction in soil surface seal hydraulic conductivity as affected by soil and sprinkler characteristics. A sealing soil infiltration model was developed using an explicit finite difference solution scheme with a transient soil seal formation model, which is unique from other studies in that it explicitly uses droplet specific power as the driving factor for formation of a soil surface seal. The model was calibrated to four specific soils using published and laboratory runoff data from rainfall simulation studies with varying droplet kinetic energies and application rates. The model was then applied to center pivot irrigation for five common sprinklers to evaluate the effect sprinkler selection has on infiltration. Due to the high susceptibility of the soils to surface sealing from water drop impact, the sprinkler with the largest wetted diameter was predicted to maximize infiltration. If a center pivot sprinkler irrigation system is operated over a bare soil at the application rates used in this study, a surface seal is going to form, and the only way to maximize infiltration depth is to apply the water over the largest time interval possible.

Last Modified: 12/18/2014
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