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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 characteristics of bare soil under sequential water application events

Authors
item KING, BRADLEY
item BJORNEBERG, DAVID

Submitted to: Irrigation Association Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: October 3, 2012
Publication Date: November 6, 2012
Citation: King, B.A., Bjorneberg, D.L. 2012. Infiltration characteristics of bare soil under sequential water application events. Proceedgins of Irrigation Association Conference, November 4-8, 2012, Orlando, Florida. 2012 CD-ROM.

Interpretive Summary: The marked reduction in infiltration rate caused by formation of a soil surface seal is a well known phenomenon but often ignored in infiltration models. The effect sequential water application events have on infiltration rate and soil surface seal formation has rarely been investigated. The objective of this study was to investigate the effect sequential water application events have on the infiltration rate of a Portneuf silt loam soil with and without water droplet impact. The Portneuf silt loam soil developed a soil surface seal that reduced infiltration rate both with and without droplet impact on the bare soil surface. Final infiltration rate was inversely related to specific power of the simulated rainfall. Either with or without water droplet impact, final infiltration rate for the Portneuf silt loam soil decreased to less than 20 mm hr-1 within three rainfall events. Given that the Portneuf silt loam soil is extremely vulnerable to surface seal development with little difference in final infiltration rate, irrigation time must be maximized and peak application rate minimized in order to maximize infiltration depth. These requirements combined with the operating characteristics of center pivot irrigation systems means that sprinklers with maximum wetted diameter need to be selected in order to maximize infiltrated depth.

Technical Abstract: The marked reduction in infiltration rate caused by formation of a soil surface seal is a well known phenomenon but often ignored in infiltration models. The effect sequential water application events have on infiltration rate and soil surface seal formation has rarely been investigated. The objective of this study was to investigate the effect sequential water application events have on the infiltration rate of a Portneuf silt loam soil with and without water droplet impact. The Portneuf silt loam soil developed a soil surface seal that reduced infiltration rate both with and without droplet impact on the bare soil surface. When the soil surface was protected during the first rainfall event, drying the soil did not increase infiltration rate for subsequent rainfall events when the soil surface was protected, but drying did increase infiltration when the soil was unprotected in the first rainfall event. Final infiltration rate was inversely related to specific power of the simulated rainfall. Either with or without water droplet impact, final infiltration rate for the Portneuf silt loam soil decreased to less than 20 mm hr-1 within three rainfall events. Given that the Portneuf silt loam soil is extremely vulnerable to surface seal development with little difference in final infiltration rate, irrigation time must be maximized and peak application rate minimized in order to maximize infiltration depth. These requirements combined with the operating characteristics of center pivot irrigation systems means that sprinklers with maximum wetted diameter need to be selected in order to maximize infiltrated depth.

Last Modified: 9/29/2014
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