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Enhancing Subsurface Drainage to Control Salinity in Dryland Agriculture
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org
Citation: 2016 10th International Drainage Symposium Conference, 6-9 September 2016, Minneapolis, Minnesota .(doi:10.13031/IDS.20162489348)
Authors: Harold Steppuhn
Keywords: agricultural drainage, alfalfa, plant emergence, pre-seeding irrigation, solar-powered pumping, soil reclamation, soil salinity, windbreaks
Abstract. Controlling the physical processes of soil salinization involves lowering ground water levels, draining the vadose zones, and leaching excess salts from root zones. Plastic drain tubing strategically placed 1.5 to 1.8 m below the surface in semiarid lands can lower water tables and drain phreatic water, but irrigation is usually required to satisfactorily leach the offending salts. In non-irrigated drylands, the leaching process depends on natural precipitation, but the drier the climate, the greater the need for more leaching water. Possible practices which tap complementary water in conjunction with subsurface drainage include: (1) establishment of roughness barriers to trap wind-borne snow, and (2) pumping water from near-surface, ground water mounds. The mean electrical conductivity of saturated paste extracts of soil sampled every fall from a field in semiarid Saskatchewan averaged 14.1 dS m-1 during the six years before the drainage was installed, 13.0 dS m-1 for two years just after drainage but before initiating blowing snow management, and 9.6 dS m-1 for the following six years. The average barley grain harvested during the six years prior to drainage yielded 330 kg ha-1, and 2414 kg ha-1 after installation of the enhanced drainage system. In a follow-up study, fall applications of 4.6 dS m-1 mounded water from a backhoe-dug well fitted with a solar-powered pump in a drainage system preceded spring seeding of alfalfa. Enhanced drainage improved mean seedling emergence from 20% to 79%. Every 28 mm of in-situ ground water applied, up to 2273 mm, increased alfalfa emergence by 1%.
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