| Growing season | Low risk (<2500 mg NO3 kg−1) | Moderate risk (2500 - 4500 mg NO3 kg−1) | High risk (>4500 mg NO3 kg−1) |
| 2003-2006 | 80.3% | 11.2% | 8.5% |
| (2034/2533) | (284/2533) | (215/2533) | |
| 2007 | 65.2% | 19.6% | 15.1% |
| (659/1010) | (198/1010) | (153/1010) | |
| 2008 | 75.8% | 13.3% | 10.8% |
| (659/869) | (116/869) | (94/869) |