Influences of soil amendments on alfalfa (Medicago sativa) production and soil properties

Millions of acres of agricultural soils in the Northern Great Plains have excessive levels of sodium, which reduces their productivity potentials. Soil function in sodium-affected soils may be improved by soil amendments, but the effectiveness of these amendments is dependent on many site-specific characteristics. This study investigated how three amendments (with three application rates), gypsum, spent lime (5, 15, and 30 ton/a), and potassium-magnesium sulfate (1, 2.5, 5 ton/a), affected alfalfa production and soil parameters at a site with subsurface tile drainage and a site without tile drainage. Notably, none of the amendments affected alfalfa production or quality at either site, although the highest rate of potassium-magnesium sulfate reduced biomass production by about 10%. After four years, the amendments did not lower the portion of Na in soil solution compared to the control at the tiled site but did at the non-tiled site. Across treatments, the effect of the tile significantly decreased EC by 0.4 dS m 1 and %Na by 3.2. Moreover, the higher rates of each amendment decreased %Na compared to initial conditions, but after four years these treatments were not different from the control (alfalfa only). This study determined that the use of a perennial crop, such as alfalfa, may be as effective as amendments in reducing the negative impacts of Na on soil properties.