|REEVES, JUSTIN - Colorado State University|
Submitted to: Proceedings of Great Plains Soil Fertility Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/3/2018
Publication Date: 3/6/2018
Citation: Liebig, M.A., Reeves, J.L., Osborne, S.L., Riedell, W.E., Schmer, M.R., Jin, V.L., Sainju, U.M. 2018. Long term soil pH change in rainfed cropping systems: is acidification systemic?. Proceedings of Great Plains Soil Fertility Conference. Vol. 17/pp. 210-214.
Interpretive Summary: Previous evaluations throughout the Great Plains suggest elevated N rates and/or use of no-tillage contributes to soil acidification in rainfed cropping systems. Soil pH responses to other management variables, such as cropping system diversity, have received less attention. Additionally, no multi-site evaluation of soil pH change under rainfed cropping has been conducted in the region. To address this need, soil pH change was determined under common rotations, management practices, and non-limed conditions throughout the northern Great Plains and western/northern Corn Belt. Data was compiled from seven long-term cropping system experiments at four sites (Sidney, MT, Mandan, ND, Brookings, SD, and Lincoln, NE), and soil pH change was measured over periods of 11 to 30 years for near-surface depths. Decreases in soil pH were observed at Sidney, Mandan, and Lincoln, whereas pH increased at Brookings. Soil pH decreases were greatest under monoculture cereal cropping, intermediate in rotations without legumes, and least in rotations including legumes. Findings from this evaluation suggest soil pH dynamics are site- and management-specific. Recommendations to ensure optimal soil pH ranges for effective herbicide use, continued micronutrient availability, and efficient nutrient cycling should be tailored accordingly.
Technical Abstract: Many soils throughout the northern Great Plains developed from deep, moderately-weathered glacial and loess deposits under prairie vegetation. Soils of this type are typically neutral to slightly acidic in near-surface depths, and slightly to strongly alkaline in subsoil depths, with high buffer capacity throughout the profile. Decades of cropping in this region has altered the chemical composition of these soils, and the potential for soil acidification, in particular, has increased due to reliance on ammonium-based fertilizers and cumulative effects of biomass export. We sought to determine the extent of soil pH change under common rotations, management practices, and non-limed conditions throughout the northern Great Plains and western/northern Corn Belt. Using data from seven long-term cropping system experiments near Sidney, MT, Mandan, ND, Brookings, SD, and Lincoln, NE, soil pH change was quantified over periods of 11 to 30 yr for near-surface depths. Decreases in soil pH were observed at Sidney, Mandan, and Lincoln, whereas pH increased at Brookings. In treatments where soil pH decreased, final values fell within very strongly- to moderately-acidic pH ranges (4.5 to 6.0). Where pH increased, changes were small (+0.1 pH units) and were still within a slightly acidic range (6.1 to 6.5). Soil pH decreases were greatest under monoculture cereal cropping (-1.31 pH units), intermediate in rotations without legumes (-0.97 pH units), and least in rotations including legumes (-0.53 pH units). Soil acidification differences among crop rotation types were likely driven by total N load from applied fertilizer. Findings from this evaluation suggest soil pH dynamics are site and management-specific.