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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 #373973
Research Project: Management Practices for Long Term Productivity of Great Plains Agriculture

Location: Soil Management and Sugarbeet Research

Title: Nitrogen fertilizer source impacts soil profile C pools more than tillage under rainfed corn

Author
item WATTS, STUART - Kansas State University
item Stewart, Catherine
item RICE, CHARLES - Kansas State University

Submitted to: Proceedings of Great Plains Soil Fertility Conference
Publication Type: Proceedings
Publication Acceptance Date: 3/10/2020
Publication Date: 3/10/2020
Citation: Watts, S.M., Stewart, C.E., Rice, C.W. 2020. Nitrogen fertilizer source impacts soil profile C pools more than tillage under rainfed corn. Proceedings of Great Plains Soil Fertility Conference.

Interpretive Summary: Soil organic carbon (SOC) increases with organic fertilizer addition or the adoption of conservation management practices such as no-till. Storing SOC improves an agricultural systems' ability to mitigate and adapt to climate change. This study was conducted to determine long-term effects of fertilizer type and tillage on profile SOC stocks. The experimental site was a rainfed continuous corn system with long-term fertilizer treatments (150 lbs N/acre) of composted organic waste (OrgF), urea (MinF) and no fertilizer addition (Ctrl) and tillage treatments of no-till (NT) and conventional till (CT). Long-term addition of OrgF reduced soil profile C loss (0-60 cm soil depth), -1.12 tons C/acre in comparison to Ctrl and MinF where 'SOC was -8.12 and -13.8 tons C/acre. In the surface 0-15 cm, OrgF increased 'SOC from the baseline the most (8.11 tons more C per acre). In summary, agricultural management effects on soil C were confined to the surface soil (15 cm deep) even with C inputs from organic fertilizer addition after 22 years.

Technical Abstract: Soil organic carbon (SOC) increases with organic fertilizer and the adoption of no-till. Soil organic C improves the ability of agricultural systems to mitigate and adapt to climate change. This study was conducted to determine the long-term effects of fertilizer type and tillage on profile SOC. The experimental site was a rainfed continuous corn (Zea mays L.) system with fertilizer treatments (150 lbs N a-1) of composted organic waste (OrgF), urea (MinF) and no fertilizer addition (Ctrl) and tillage treatments of no-till (NT) and conventional till (CT). Change in SOC and d13C was measured through the soil profile after 22 years. The change in SOC was calculated from a baseline sampling at the start of the experiment using equivalent soil mass to determine soil profile changes over time. Long-term addition of OrgF reduced profile C loss (0-60 cm), -1.12 tons C a-1 in comparison to Ctrl and MinF where 'SOC was -8.12 and -13.8 tons C a-1. In the surface 0-15 cm, OrgF increased 'SOC from the baseline the most (8.11 tons C a-1). No-till sequestered more C in the 0-5 cm layer than CT, while CT sequestered more C than NT in the 5-15 cm layer. The compost d13C signature was also evident with depleted soil d13C from 0-15 and 30-45 cm. Within the 30-45 cm depth, NT OrgF decreased losses of SOC (-1.70 tons C a-1) compared to CT OrgF (-5.75 tons C a-1). Although d13C was elevated with OrgF in the 15-45 cm depths, this did not result in gains in soil C. Although not significant, soil profile C to 45 and 60 cm depths showed greater net gains in soil C with NT OrgF (6.42 and 0.29 tons C a-1) than CT OrgF (1.41 and -3.34 tons C a-1). In summary, surface management effects on soil C were confined to the surface 15 cm even with additional C inputs after 22 years. In these annual cropping systems, considerations need to made for deep-rooted crops and rotations to deliver C inputs into the subsoil; however, this must include no-tillage as tillage loses the benefits of additional C inputs.