REFERENCE:
Puntel, L. A., Sawyer, J. E., Barker, D. W., Dietzel, R., Poffenbarger, H., Castellano, M. J., et al. (2016). Modeling long-term corn yield response to nitrogen rate and crop rotation. Front. Plant Sci. 7, 1630. doi:10.3389/fpls.2016.01630.
Puntel, L. A., Sawyer, J. E., Barker, D. W., Dietzel, R., Poffenbarger, H., Castellano, M. J., et al. (2016). Modeling long-term corn yield response to nitrogen rate and crop rotation. Front. Plant Sci. 7, 1630. doi:10.3389/fpls.2016.01630.
OBJECTIVES:
Quantify model prediction accuracy before and after calibration, and report calibration steps
Compare crop model-based techniques in estimating optimal N rate for corn
Utilize the calibrated model to explain factors causing year to year variability in yield and optimal N
METHODOLOGY:
We tested the ability of the Agricultural Production Systems sIMulator (APSIM) to simulate corn [Zea mays L.] and soybean [Glycine max L.] yields, the economic optimum N rate (EONR) using a 16-year field-experiment dataset from central Iowa, USA that included two crop sequences (continuous corn and soybean-corn) and five N fertilizer rates (0, 67, 134, 201, and 268 kg N ha-1) applied to corn. We evaluate APSIM the model performance of a “blind phase” (uncalibrated model) where management and cultivar information were used, and a “calibrated phase” (calibrated model) where crop yield and soil organic carbon (SOC) data were provided into the model.
Quantify model prediction accuracy before and after calibration, and report calibration steps
Compare crop model-based techniques in estimating optimal N rate for corn
Utilize the calibrated model to explain factors causing year to year variability in yield and optimal N
METHODOLOGY:
We tested the ability of the Agricultural Production Systems sIMulator (APSIM) to simulate corn [Zea mays L.] and soybean [Glycine max L.] yields, the economic optimum N rate (EONR) using a 16-year field-experiment dataset from central Iowa, USA that included two crop sequences (continuous corn and soybean-corn) and five N fertilizer rates (0, 67, 134, 201, and 268 kg N ha-1) applied to corn. We evaluate APSIM the model performance of a “blind phase” (uncalibrated model) where management and cultivar information were used, and a “calibrated phase” (calibrated model) where crop yield and soil organic carbon (SOC) data were provided into the model.
Figure 1. Sixteen year mean crop yield response to N fertilizer rate (A, D, and G panels), and observed versus simulated crop yields across years and N rate (B, C, E, F, H, and I). Points are observations or simulations, continuous lines are regression fits from Eqs. 1–3, and broken lines show 1:1 relationship. mean square error for both calibrated (RRMSE) and uncalibrated model (RRMSE_un) are shown for each year