| K-rate (kg/ha) | Fall 2004 | Spring 2005 | Fall 2005 | Spring 2006 | Fall 2006 | Spring 2007 |
| soil-test K (mg∙kg−1) | ||||||
| 0 | 105a† | 97a | 86a | 90a | 92a | 94a |
| 28.2 | 100a | 97a | 94a | 97a | 110a | 111b |
| 56.4 | 105a | 110a | 100a | 111a | 114a | 108b |
| 84.7 | 114a | 110a | 115b | 133b | 133b | 117b |
| 112.9 | 122b | 122b | 125b | 147b | 147b | 131c |
| 141.1 | 130b | 132b | 146c | 169c | 182c | 159d |
| P value | <0.0001 | 0.0002 | <0.0001 | <0.0001 | <0.0001 | <0.0001 |