Measured and Simulated Carbon Dynamics in Midwestern U.S. Corn‐Soybean Rotations
Wacha, K. M.
Sauer, T. J.
Hatfield, J. L.
Prueger, J. H.
DOI: https://doi.org/10.1029/2020GB006685
Persistent URL: http://resolver.sub.uni-goettingen.de/purl?gldocs-11858/8563
Sauer, T. J.; 2 USDA‐ARS National Laboratory for Agriculture and the Environment Ames IA USA
Hatfield, J. L.; 2 USDA‐ARS National Laboratory for Agriculture and the Environment Ames IA USA
Prueger, J. H.; 2 USDA‐ARS National Laboratory for Agriculture and the Environment Ames IA USA
Abstract
Corn (Zea mays L.) and soybean (Glycine max [L.] Merr.) production dominate Midwestern U.S. agriculture and impact the regional carbon and nitrogen cycles. Sustaining soil carbon is important for corn‐soybean production (CS); however, quantifying soil carbon changes requires long‐term field measurements and/or model simulations. In this study, changes in soil organic (SOC), inorganic (SIC), and total (TC) carbon; pH; total nitrogen (TN); and net ecosystem production (NEP) were measured in a conventional corn‐soybean rotation in central Iowa. Soil samples (n = 42; 0–120 cm depth) were collected from two adjacent fields in 2005 and 2016. Eddy‐flux stations set up in the fields continuously monitored NEP from 2005–2016, and net biome production (NBP) was calculated using yield records. The DayCENT model was used to simulate the effects of conventional management practices on soil carbon and calibrated with field‐measured NEP and SOC. Measured soil TC (0–120 cm) decreased by −14.19 ± 6.25 Mg ha−1, with highest reductions in SOC and SIC (p < 0.05) at 0–15 and 90–120 cm, respectively. Measured TN decreased by −0.7 ± 0.29 Mg ha−1 with N‐accumulation at 60–90 cm (p < 0.05). Eddy‐flux NBP decreased by −13.19 ± 0.05 Mg ha−1. Soil and eddy‐flux records show a carbon reduction by −1.14 ± 0.63 and −1.20 ± 0.06 Mg ha−1 yr−1, respectively. The validated DayCENT model suggests that all SOC pools declined. We postulate that conventional CS production has adverse effects on C and N dynamics in Midwestern United States.
Key Points:
Eddy covariance shows a decrease in ecosystem C after 11 yr of corn‐soybean production. Soil inorganic C decreased in 90–120 cm, and organic C decreased in 0–15 cm after 11 yr. DayCENT simulations suggest current conventional corn‐soybean rotations decrease all SOC pools in topsoil layer.