Combining gypsum with establishment of perennial vegetation improved the restoration of a salt-affected soil in the Northern Great Plains

Abstract

Classical saline-sodic soil management approaches are to apply gypsum or elemental sulfur (S), improve soil drainage, and irrigate with enough water to leach soluble salts out of the soil. However, these protocols do not incorporate the soil health principles of limiting soil disturbance, keeping the soil covered, providing a living root, and increasing species diversity. The objective of this study was to determine if combining chemical amendments (gypsum and elemental S) with the soil health principles of limiting soil disturbance, providing soil cover, and establishing an active root improved soil health in a lowland, salt-affected soil. The soil health metrics of soil electrical conductivity (EC1:1), sodium concentration (mg Na+ kg 1 soil), percentage sodium (%Na+), Na:EC ratio, wet aggregate stability, and water infiltration were compared in an upland and lowland soil with vegetation treatment alone or vegetation plus chemical amendments. The vegetation experiment was established at two landscape positions as a randomized complete block design (RCBD) that was then broken into a split-plot design to include chemical amendments. The vegetation main plots were corn (Zea mays L.), two perennial grass mixtures (Mix 1 and Mix 2), and a no-vegetation control. The split-plots were chemical amendments (gypsum, elemental S, and no-amendment). Soil samples to a 15 cm depth were analyzed for EC1:1 and Na+ concentration in 2018, 2019, 2020, and 2022. We t aggregate stability and water infiltration was measured in 2020 and 2022. In the saline-sodic lowland soil from 2020 to 2022, the application of gypsum plus vegetation decreased EC1:1 (1.71 1.43 dS m 1) and Na+ (1,445 578 ppm) concentration and increased (p = 0.05) water infiltration from near impermeable to 362 mm h 1. Elemental S plus vegetation did not produce a change in the measured soil health metrics from 2020 to 2022. These results were attributed to the combined effect of gypsum plus vegetation providing soil cover and physical channels for water and Na+ transport, whereas elemental S plus vegetation was unsuccessful due to limited microbial activity for S oxidation. These findings suggest that an important step in restoring soil health to saline-sodic areas is the establishment of perennial plants. The application of gypsum has the potential to add other benefits, whereas the addition of elemental S had no measurable impact.