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ARS Home » Midwest Area » Ames, Iowa » National Laboratory for Agriculture and The Environment » Soil, Water & Air Resources Research » Research » Publications at this Location » Publication #356281
Title: Measured and simulated carbon dynamics in Midwestern U.S. corn-soybean rotations

Author
item DOLD, CHRISTIAN - Orise Fellow
item WACHA, KENNETH - Orise Fellow
item Sauer, Thomas
item Hatfield, Jerry
item Prueger, John

Submitted to: Global Biogeochemical Cycles
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/15/2020
Publication Date: 11/25/2020
Citation: Dold, C., Wacha, K.M., Sauer, T.J., Hatfield, J.L., Prueger, J.H. 2020. Measured and simulated carbon dynamics in Midwestern U.S. corn-soybean rotations. Global Biogeochemical Cycles. 35(1). Article e2020GB006685. https://doi.org/10.1029/2020GB006685.
DOI: https://doi.org/10.1029/2020GB006685

Interpretive Summary: Corn-soybean rotations can affect soil carbon and other parameters but assessing these changes require long-term records. In this study, soil pH, nitrogen, and carbon were analyzed in a conventional corn-soybean rotation in Iowa from 2005-2016. Soil samples were taken to a depth of 120cm at 42 locations in a 50 x 50m grid in two adjacent fields in 2005 and 2016. These samples were analyzed for soil organic and inorganic carbon, nitrogen, and soil pH. Eddy-flux stations monitored the carbon flux continuously during the same period. Total amount of carbon decreased substantially, with highest soil organic carbon losses to a depth of 30cm and highest soil inorganic carbon losses to the 90–120cm layer. The decrease in organic carbon was attributed to continuous tillage, while inorganic carbon reduction could indicate weathering of carbonates in the soil. Total N decreased as well in these soils despite nitrogen application and crop residues. Soil pH decreased to a depth of 15 cm, probably due to acidifying anhydrous nitrogen application. Also, the carbon flux measurements showed a reduction in carbon from these fields. The discrepancy between methods derives from difficulties of carbon balance quantification. Yet, both methods indicate that the conventional corn-soybean rotation system is unsustainable, as important soil parameters deteriorated. This research is important to researchers and extensionists, who want to quantify the impact of crop production on soil quality.

Technical Abstract: Corn [Zea mays L.] -soybean [Glycine max (L.) Merr.] rotations can affect soil carbon (C) and other parameters but assessing these changes require long-term records. In this study, soil pH, nitrogen (N), and C pools and fluxes (Fc) were analyzed in a conventional corn-soybean rotation in Iowa from 2005-2016. Soil samples were taken to a depth of 120cm at 42 locations in a 50 x 50m grid in two adjacent fields in 2005 and 2016. These samples were analyzed for soil organic (SOC) and inorganic (SIC) C, total N, and soil pH. Eddy-flux stations monitored Fc continuously during the same period, and net biome production (NBP) was calculated. Mean (± SE) total C in 0–120cm decreased by -14.72 ± 6.05 Mg ha-1, with highest SOC and SIC losses to a depth of 30cm and to the 90–120cm layer, respectively. The SOC decrease was attributed to continuous tillage, while SIC reduction could indicate carbonate weathering. Total N decreased by -0.72 ± 0.44 Mg ha-1, despite N application and crop residues. Soil pH decreased in 0 – 15 cm by -0.44 ± 0.11, due to acidifying anhydrous N application. The NBP also decreased by -13.19 ± 0.05 Mg ha-1. Both soil analysis and eddy-flux records show a reduction of C by -1.34 ± 0.55 and -1.20 ± 0 Mg ha-1 yr-1, respectively. The discrepancy between methods derives from difficulties of C balance quantification. Yet, both methods indicate that the conventional corn-soybean rotation system is unsustainable, as important soil parameters deteriorated.