Table 9.
Site-specific fitted regression equations for maize yield (t/ha) with added phosphate (P2O5) as a covariate. (−) indicates that no polynomial fit to the data was obtained
| Location | Year | Fitted equation for yield | Fit type | P value | R2 |
|---|---|---|---|---|---|
| DeWitt, NE | 2006 | Y = 14·6–0·003 × P2O5–0·004 (P2O5–10)2 | Quadratic | 0·030 | 0·279 |
| Jeffers, MD | 2006 | Y = 11·5 + 0·014 × P2O5 | – | 0·416 | 0·042 |
| Fergus Falls, MD | 2006 | Y = 8·2 + 0·016 × P2O5 | – | 0·483 | 0·038 |
| Aurora, NE | 2009 | Y = 14·6–0·008 × P2O5 | – | 0·401 | 0·032 |
| Centerville, SD | 2009 | Y = 11·1+ 0·042 × P2O5 | Linear | 0·033 | 0·191 |
| Fergus Falls, MN | 2009 | Y = 9·8 + 0·040 × P2O5 | Linear | 0·043 | 0·173 |
| Garden City, KS | 2009 | Y = 14·6–0·015 × P2O5 | – | 0·365 | 0·037 |
| Groom, TX | 2009 | Y = 11·1 + 0·084 × P2O5 | – | 0·001 | 0·419 |
| Aurora, NE | 2010 | Y = 15·45 + 0·002 × P2O5 | Linear | 0·401 | 0·001 |
| Britton, SD | 2010 | Y = 10·9 + 0·010 × P2O5 | – | 0·431 | 0·028 |
| Centerville, SD | 2010 | Y = 11·4 + 0·006 × P2O5 | – | 0·704 | 0·007 |
| Nebraska, NE | 2010 | Y = 9·9–0·014 × P2O5 | – | 0·300 | 0·053 |