Stem infusion of nitrogen‐15 to quantify nitrogen remobilization in maize

Abstract

Nitrogen (N) use efficiency (NUE) of fertilizer N can be accurately estimated by tracing the fate of soil applied labelled fertilizer, but 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 labelled ¹⁵N solution was conducted at Ottawa, Ontario (45°22'N, 75°43'W) for two years to determine whether stem infused ¹⁵N could be used to quantify N remobilization and the contribution of remobilized N to the grain. A current stay‐green commercial hybrid was grown at three fertilizer N rates and infused with 30 mL ¹⁵N solution [35.7 mmol N as ¹⁵NH₄ ¹⁵NO₃ at 99.2 ¹⁵N% atom enrichment (a.e.)] into the internode below the primary cob at anthesis. The control plants were infused with distilled water. Sampling occurred at 3 d, 2 wk and 5 wk after anthesis and at physiological maturity. Each plant was subdivided into ten components. Dry weight, total N concentration and ¹⁵N% a.e. were determined for each component. Thirty mL of dilute N solution plus 10 mL of distilled water was taken up within 4 to 6 hours after infusion. At 3 d after infusion, infused ¹⁵N moved out of the internode where it was infused, into dominant sinks, with more than 40% in the reproductive components (cob, husk, and kernels), 30% in leaves above the ear, and another 15 to 20% in the upper stem. By physiological maturity, 65 to 75% of infused ¹⁵N was deposited in the kernels. Between 59 and 82% of kernel N was remobilized from non‐kernel components, whereas 18 to 41% was derived from N uptake during grain fill. These findings indicate that stem infusion is a useful technique to study N remobilization.

Notes

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