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Simulating Long-Term and Residual Effects of Nitrogen Fertilization on Corn Yields, Soil Carbon Sequestration, and Soil Nitrogen Dynamics

^a Joint Global Change Research Institute, Pacific Northwest National Laboratory, University of Maryland, 8400 Baltimore Avenue, Suite 201, College Park, MD 20740
^b USDA-ARS, South Atlantic Area, Coastal Plains Soil, Water, and Plant Research Center, 2611 West Lucas Street, Florence, SC 29501
^c Texas A&M University, Blacklands Research Center, 808 East Blacklands Road, Temple, TX 76502

^* Corresponding author (allison.thomson{at}pnl.gov)

Received for publication June 28, 2005. Soil carbon sequestration (SCS) has the potential to attenuate increasing atmospheric CO₂ and mitigate greenhouse warming. Understanding of this potential can be assisted by the use of simulation models. We evaluated the ability of the EPIC model to simulate corn (Zea mays L.) yields and soil organic carbon (SOC) at Arlington, WI, during 1958–1991. Corn was grown continuously on a Typic Argiudoll with three N levels: LTN1 (control), LTN2 (medium), and LTN3 (high). The LTN2 N rate started at 56 kg ha^–1 (1958), increased to 92 kg ha^–1 (1963), and reached 140 kg ha^–1 (1973). The LTN3 N rate was maintained at twice the LTN2 level. In 1984, each plot was divided into four subplots receiving N at 0, 84, 168, and 252 kg ha^–1. Five treatments were used for model evaluation. Percent errors of mean yield predictions during 1958–1983 decreased as N rate increased (LTN1 = –5.0%, LTN2 = 3.5%, and LTN3 = 1.0%). Percent errors of mean yield predictions during 1985–1991 were larger than during the first period. Simulated and observed mean yields during 1958–1991 were highly correlated (R² = 0.961, p < 0.01). Simulated SOC agreed well with observed values with percent errors from –5.8 to 0.5% in 1984 and from –5.1 to 0.7% in 1990. EPIC captured the dynamics of SOC, SCS, and microbial biomass. Simulated net N mineralization rates were lower than those from laboratory incubations. Improvements in EPIC's ability to predict annual variability of crop yields may lead to improved estimates of SCS.

Abbreviations: D_b, bulk density • EPIC, Environmental Policy Integrated Climate • HI, harvest index • LAI, leaf area index • NMN, net nitrogen mineralization • RMSE, root mean square error • RUE, radiation use efficiency • SCS, soil carbon sequestration • SOC, soil organic carbon • SOM, soil organic matter