The impact of different nitrogen (N) management strategies (rate, split-N application, foliar-N application, legume pre-cropping) were assessed for their effectiveness in reversing the reduction of grain protein content in order to maintain grain quality of wheat (cv. Yitpi) under elevated CO2 (eCO2) using Free Air Carbon Dioxide Enrichment (FACE).
Preliminary results show that under eCO2 conditions the plant biomass, grain yield and grain size increased and that grain protein content decreased when no N fertiliser was applied (N0). Significant grain yield responses to increasing rates of N fertiliser (applied at sowing) were observed in Yitpi, with the grain yield under eCO2 conditions increasing by 63% when 100 kg N/ha (N100) was applied compared with N0; an increased response (59%) was also observed under ambient CO2 conditions. The largest grain yield response for a N management strategy compared with N0 under eCO2 conditions was when Yitpi was grown after prior rotation with annual medic pasture (M), with an increase of 74%. Grain protein increased significantly (31%) under eCO2 conditions at N100 compared with N0, however it seems that vegetative growth demand ‘took preference’ with an increase in dry matter (DC90) of 101% under eCO2 conditions at N100 compared with N0. Under ambient CO2 only 50 kg N/ha at sowing was required to gain a similar increase in grain protein content. When comparing the grain protein content of Yitpi sown into medic stubble (M) to that at N0, there was a significant increase (P = 0.05) at ambient CO2 conditions, however, under eCO2 conditions no significant response observed.