Nitrogen concentrations in spring wheat at several growth stages

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Abstract
Diagnosis of N deficiency in spring wheat (Triticum aestivum L.) is important in the North Central region because it is the principal grain crop and N is the nutrient most often limiting its growth. Plant analysis may provide a means by which this objective can be realized. This study was undertaken to establish N levels of sufficiency and deficiency in spring wheat at several growth stages. Five cultivars of spring wheat were grown in the field at rates of 0, 40, 80, and 160 kg/ha of N on a Maddock sandy loam (sandy, mixed Udorthentic Haploborolls) for two years. Plant samples were collected at Feekes growth stages 3, 5–6, 9–10, and 10.5–10.5.1. Nitrogen concentration trends in the plant tissue showed a rapid drop between stages 3 and 10.5–10.5.1. Nitrogen concentration growth curves exhibited a curvilinear pattern at stages 5–6, 9–10 and 10.5–10.5.1, and a linear relationship at stage 3. For the whole plant samples N concentrations of 5.2–5.6%, 4.2–5.1%, 2.4–3.5% and 1.8–2.6% at stages 3, 5–6, 9–10 and 10.5–10.5.1 were sufficient. For leaf blade samples N concentrations of 4.1–5.0% and 3.6–4.5% at stages 9–10 and 10.5–10.5.1 were sufficient. Cultivar effects on N concentration were sometimes significant but the effects were inconsistent between two seasons or within a given season.