Percent Sodium, Electrical Conductivity, and Alfalfa Yield Affected By Application of Sodic-Soil Amendments.

In the northern Great Plains of the United States, 10 million ha of land are negatively impacted by sodic soils. Sodic soils typically have poor chemical and physical conditions due to the excess amount of monovalent Na relative to other cations on exchange sites and in the soil solution (high Na, low EC). A three-year field study with a random complete block design (RCBD) replicated four times on surface (non-tiled) and subsurface (tile) drained sites was conducted, both planted to alfalfa. Flue-gas desulfurization gypsum (FGDG) and sugar beet processing by-product lime (spent lime) were applied at rates of 11.2, 33.6, 67.2 Mg ha^-1, and langbeinite was applied at rates of 2.2, 5.6, and 11.2 Mg ha^-1. Alfalfa yields did not show any statistical differences on the tiled site, but the yields were significantly reduced for the two high rates of langbeinite at the non-tiled site. Forage quality was not significantly impacted by the treatments and was within prime quality feed criteria. Although significant changes were not seen across treatments for %Na, the FGDG and spent lime treatments had the most positive impact on the %Na and did not reduce alfalfa yield or quality.