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ARS Home » Plains Area » Fort Collins, Colorado » Center for Agricultural Resources Research » Soil Management and Sugarbeet Research » Research » Publications at this Location » Publication #373970

Research Project: Management Practices for Long Term Productivity of Great Plains Agriculture

Location: Soil Management and Sugarbeet Research

Title: Nitrogen fertilization and long-term no tillage impacts on soil properties and deep soil c storage under irrigation

Author
item Stewart, Catherine
item Manter, Daniel
item Delgado, Jorge
item Del Grosso, Stephen - Steve
item Calderon, Francisco
item HECKMAN, KATE - FOREST SERVICE (FS)
item SNELL, KATE - UNIVERSITY OF COLORADO

Submitted to: Proceedings Great Plains Soil Fertility Conference
Publication Type: Proceedings
Publication Acceptance Date: 3/10/2020
Publication Date: 3/10/2020
Citation: Stewart, C.E., Manter, D.K., Delgado, J.A., Del Grosso, S.J., Calderon, F.J., Heckman, K., Snell, K. 2020. Nitrogen fertilization and long-term no tillage impacts on soil properties and deep soil c storage under irrigation. Proceedings Great Plains Soil Fertility Conference.

Interpretive Summary: The net soil greenhouse gas mitigation potential (of conservation agricultural management practices) is strongly influenced by the direction and magnitude of soil organic C (SOC) change in deep soil layers (>6”). Deep SOC can be susceptible to loss from the addition of new, labile organic C. We examined long-term soil C dynamics (organic and inorganic) 13 years after conversion to no-tillage (NT) under varying nitrogen fertilizer rates (0 or 220 lbs a-1). Nitrogen fertilizer had little effect on SOC and soil inorganic C except in the 0-3” layer. After NT adoption, deep soil C became older. These results indicate that deep soil C (both organic and inorganic) is surprisingly dynamic and susceptible to loss, despite conservation management practices.

Technical Abstract: The net soil greenhouse gas mitigation potential of conservation agricultural management practices is strongly influenced by the direction and magnitude of soil organic C (SOC) change in deep soil layers (>6”). Deep SOC is typically old, highly processed, and consists of microbial products and root exudates associated with clay and other minerals. However, it can be susceptible to decomposition and priming from the addition of new, labile organic C. We examined long-term soil C dynamics (organic and inorganic) 13 years after conversion to no-tillage (NT) under varying nitrogen fertilizer rates (0 or 220 lbs a-1). We present preliminary data from throughout the soil profile (0-4’) of '13C of SOC and SIC, 14C, and organic and inorganic chemical composition by FTIR. Although there was surface (0-3”) accumulation of new, corn-derived-C, it was lost from the deeper soils (>3”). Nitrogen fertilizer had little effect on SOC and SIC except in the 0-3” layer. After NT adoption, deep soil C became older, from both '13 SOC and 14C data. Soil inorganic C increased at the two deepest depths, which was confirmed by FTIR. The '13SIC suggested disequilibrium of C sources with carbonate minerals after only 13 years. These results indicate that deep soil C (both organic and inorganic) is surprisingly dynamic and susceptible to loss, despite conservation management practices.