FIGURE 2.

Corn yield response to N fertilizer for the soybean-corn (SC) cropping system. The blue points with standard errors (n = 4) indicate the observations. The gray, red, and green points indicate uncalibrated, calibrated and validated simulations from the Agricultural Production Systems sIMulator (APSIM) model. Continuous lines are regression fits from Eqs. 1–3. When lines are not shown it means that Eqs. 1–3 did not converge. Relative root mean square error for both calibrated (RRMSE) and uncalibrated model (RRMSE_un) are shown for each year.