Stem‐infused nitrogen‐15 enrichment for evaluation of nitrogen use in maize

Nitrogen use efficiency (NUE) of N fertilizer can be accurately estimated by tracing the fate of soil applied 15N‐labeling. However, the quantity of N remobilization from non‐kernel components into kernels in maize (Zea mays L.) plants is difficult to determine. A field experiment involving stem infusion with four levels of enriched 15N solution plus non‐infusion or infusion with water was conducted at Ottawa (45°22'N, 75°43'W), Canada to determine the effect of 15N atom % enrichment (a.e.) on physiological processes associated with NUE. At anthesis, 30 mL of 35.7 mmol N solution as 15NH4 15NO3 at 5.0 (N05), 33.0 (N33), 66.0 (N66) and 99.2 (N99) 15N% a.e. was infused into the internode below the primary cob. The control plants were infused with distilled water. Photosynthesis was measured at 2, 4, 6, 24 h and 1 wk after infusion. Plants were sampled and separated into components at 4 d after anthesis (D4A) and at physiological maturity (PM). Dry weight, total N concentration, NH4‐ and NO3‐N, and ...