Updated June 25, 2018:
Sodium is a natural dispersant. Soil dispersion reduces pore sizes which leads to the blocking or clogging of soil pores and ultimately reduces the function of the soil. In addition, after drying, sodium-affected soils (sodic soils) become “hard-set” which inhibits proper root and plant growth. Unfortunately, millions of acres of North Dakota soils suffer from too much sodium which ultimately reduces their productivity potentials. Identification and understanding of these problem soils is key to proper management, and for understanding these soils’ economic potentials.
We conducted a four-year field study, starting in spring of 2014, looking at if sodic-soil amendments and alfalfa could improve soil health for long-term improved soybean production on soils impacted by sodium and salinity. Amendments included three rates each of flue-gas desulfurization gypsum (5, 15, and 30 tons/acre), sugar beet spent lime (5, 15, and 30 tons/acre), and potassium-magnesium sulfate (1, 2.5, and 5 tons/acre). The two soils used for this study were in the same NRCS soil-mapping unit but varied in properties, and one soil was tiled and the other soil was not tiled. The fundamental objective of this study was to improve soil properties for improved soybean production.
View uploaded report
Overall, the amendments and their rates of application neither decreased or increased alfalfa yields or quality compared to control plots. However, the two highest application rates of gypsum and the highest rate of K-Mg to the tiled site increased the IDC rating to ‘very high’ compared to the control plot. No changes to IDC rating was observed at the non-tiled site. The two highest rates of gypsum, the highest rate of spent lime, and the highest rate of K-Mg reduced the potential for swelling and/or dispersion to ‘medium’ compared to the control, which was ‘high.’ The potential for swelling and/or dispersion was ‘low’ in all plots at the non-tiled site.