Pearson correlation coefficients between root expression of key N metabolism genesa and plant and soil variablesb measured across 13 organic Roma-type tomato fields in Yolo Co., California, USA.

All soil variables are from 0–15 cm surface soil. For units of each variable, see Table 4. Correlations significant at p a AMT1.1 and AMT1.2: high-affinitity NH4+ transporters; NRT2.1: high-affinity NO3- transporter; Nii: nitrite reductase; GS1: cytosolic glutamine synthetase; GS2: plastidic/chloroplastic glutamine synthetase; NADH-GOGAT: glutamate synthase.b PMN: potentially mineralizable N; MBC: microbial biomass C; MBN: microbial biomass N; EOC: extractable organic C; EON: extractable organic N; POXC: permanganate oxidizable C; GWC: gravimetric water content.Pearson correlation coefficients between root expression of key N metabolism genesa and plant and soil variablesb measured across 13 organic Roma-type tomato fields in Yolo Co., California, USA.