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

0.802

±0.0159

0.115

±0.0063

0.082

±0.0086

2007

0.656

±0.0602

0.184

±0.0213

0.160

±0.0342

2008

0.757

±0.0549

0.138

±0.0231

0.105

±0.0251