This Norwegian pot experiment tested how nitrogen rate and timing, and soil plus foliar zinc and iron, change zinc and iron in wheat grain. Soil and foliar zinc and iron with a single nitrogen dose raised grain zinc by 46% compared with growth-media application alone. Imaging showed zinc concentrated with iron in the germ, crease and aleurone rather than the starchy endosperm.
Key numbers
- Soil plus foliar zinc and iron, with 120 kg N/ha at sowing, increased grain zinc by 46% and iron by 35% over growth-media application only (Abstract, p. 1).
- Grains chosen for imaging contained relatively high zinc, 42 to 99 mg/kg, and iron, 44 to 115 mg/kg (Methods, p. 4).
- Growth media received zinc at 10 mg/kg; foliar spray supplied 6 mg zinc per pot as zinc sulfate (Methods, p. 3).
- Analytical accuracy checked with three replicates of SRM 1567a wheat flour; RSD under 5% (Methods, p. 4).
Methods (brief)
Wheat was grown in an artificial sand, peat and kaolin medium in a growth chamber. Grain zinc was measured by ICP-OES after microwave nitric acid digestion; distribution within cut grains was mapped by scanning macro X-ray fluorescence and laser ablation ICP-MS.
Evidence fitness
The study supports the observation that agronomic practice changes grain zinc and that zinc sits mainly in the germ and outer layers that milling removes. Its numbers come from a controlled pot trial, not from field or market wheat.
Limitations
Grain zinc means by treatment are shown only in figures. The localization grains were selected for high zinc. No untreated control pot was included because the medium supplied all nutrients.
Related evidence
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