Influences of soil amendments on alfalfa production and soil properties

Authors: DESUTTER, THOMAS - North Dakota State University; BREKER, MARIA - North Dakota State University; CHATTERJEE, AMITAVA - North Dakota State University; O'Brien, Peter; WICK, ABBY - North Dakota State University

Submitted to: Forage and Grazinglands
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/15/2020
Publication Date: 7/24/2020
Publication URL: https://handle.nal.usda.gov/10113/7071255
Citation: DeSutter, T.M., Breker, M., Chatterjee, A., O'Brien, P.L., Wick, A. 2020. Influences of soil amendments on alfalfa production and soil properties. Forage and Grazinglands. 6:e20043. https://doi.org/10.1002/cft2.20043.
DOI: https://doi.org/10.1002/cft2.20043

Interpretive Summary: Excessive levels of sodium ions (Na+) in the soil can change both the way that water infiltrates at the soil surface and how water moves within the soil profile. When soils with excessive sodium (i.e., sodium-affected soils) are used to grow agricultural commodities, these changes to soil water movement reduce overall crop or forage production. Many land managers apply soil amendments to reduce the negative influence of excessive sodium in soils, but the effectiveness of these amendments varies widely because of site-specific characteristics like soil pH, soil texture, climate, and agronomic management. This research describes a study on sodium-affected soils investigating how alfalfa production and some soil properties are affected by three different amendments – gypsum, lime, and potassium-magnesium sulfate – applied at low, medium, or high rates. None of the amendments changed the amount or quality of alfalfa grown at either a site with subsurface tile drainage or a site without subsurface tile drainage. After four years, the levels of two important chemical properties of sodium-affected soils, soil electrical conductivity and relative proportion of Na in the soil solution, had decreased. However, they were not decreased any more after soil amendment application than in soils with no amendment applied. Thus, 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. This information is very useful for land managers in determining whether to apply soil amendments, as these findings suggest that a single application will not improve soil properties or crop production enough to warrant the cost of application.

Technical Abstract: 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.