Fig. 5.

BNI function impact on N₂O emissions and nitrifying populations in root-zone soils of field-grown wheat lines ( SI Appendix, Study 6a). (A) N₂O emissions from root-zone soils of BNI isogenic lines, MUNAL control versus BNI-MUNAL. The root-zone soils used in this study were collected from MUNAL control and BNI-MUNAL (from 250 kg ⋅ N ⋅ ha⁻¹ field plots). A total of 5 g air-dried soil was incubated with 250 ppm N [as (NH₄)₂SO₄] using a 100-mL glass vial at 20 °C with 80% relative humidity in the incubator; soil moisture levels were maintained at 60% water-filled pore space during the incubation period. Values are means ± SE of four replications (see SI Appendix, Fig. S7B for cumulative N₂O emissions over the 21-d period and for a statistical analysis of these results). (B) Influence of BNI-MUNAL on AOA populations in root-zone soils of field-grown plants. These results suggest that BNI-MUNAL suppressed AOA ranging from 20 to 36% depending on the nitrogen treatment of field plots. Root-zone soil samples were taken 16 d after the application of the second split nitrogen fertilizer. Values are means ± SE of four replications. Based on a three-way analysis of data using a General Linear Model model with SYSTAT 14.0; significant (P < 0.005) genetic stock effect on AOA; significant (P < 0.005) nitrogen treatment effect on AOA populations in rhizosphere soils.