Table 1.
Mean economic optimum N rate (EONR, kg N ha-1) across 16-years for: observed, Obs; un-calibrated Agricultural Production Systems sIMulator (APSIM) model, Unc; calibrated model, Cal; and the return to N approach from the calibrated model, RTN.
| Obs | Unc | Cal | RTN | Obs-Unc | Obs-Cal | Obs-RTN | ||
|---|---|---|---|---|---|---|---|---|
| Rotation | Mean values | Differences | ||||||
| Average of years ± SD1 | CC | 188 ± 42 | 190 ± 82 | 225 ± 33 | 176 ± 21 | -2 | -37 | 12 |
| SC | 149 ± 48 | 99 ± 71 | 137 ± 43 | 118 ± 30 | 50 | 12 | 31 | |
| Pooled2 | CC | 187 | 226 | 228 | 195 | -39 | -41 | -8 |
| SC | 158 | 140 | 147 | 140 | 18 | 10 | 18 | |
Absolute differences between EONR-Obs and simulations are also shown. Continuous corn, CC and soybean-corn rotation, SC.
1 Individual annual optimum N rate estimates were averaged across 16-years and the standard deviation (SD) calculated.
2 Individual annual corn yield values were first averaged across years and then the optimum N rates estimated.