Thursday, 10 November 2005 - 9:45 AM
323-5

Salt Accumulation with Subsurface Drip Irrigation.

TL Roberts1, SA White2, and Thomas Thompson2. (1) University of Arizona Dept. of Soil Water and Environmental Sciences, 892 A E Glenn Street, Tucson, AZ 85719, (2) University of Arizona, Room 429 Shantz Building #38, PO Box 210038, Tucson, AZ 85721

Subsurface drip irrigation (SDI) can result in accumulation of soluble salts at or near the soil surface. This can adversely affect seed germination and emergence. Use of sprinklers to minimize salt concentrations near the soil surface is a viable, but expensive, alternative. Our objective was to evaluate the effects of germination method (irrigation with SDI or sprinklers), depth of SDI tubing (18 and 25 cm), and irrigation water salinity (1.6 and 2.5 dS m-1) on salt distribution after two growing seasons. Bromide was used during the experiment as a conservative tracer for water movement and salt accumulation from the drip tubing. Results after the first season showed that the highest salt concentrations were in the top 3 cm of soil. Soil EC in the top 3 cm was as high as 11 dS m-1 when irrigated with the more saline water. Below 3cm, soil EC dropped significantly and remained constant to a depth of 90 cm. Bromide distributions were similar, with the highest Br- concentrations in the top 3 cm of the profile. After the second season, the highest salt and Br- concentrations were at about 25 cm depth, probably due to >5 cm of rainfall that occurred at the end of the growing season. Knowledge of salt distribution following growing seasons would allow producers more flexibility in managing salt accumulation, and could eliminate expenses associated with unnecessary leaching practices using sprinklers.

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