Mineral-nutrient synergism and dilution responses to nitrogen fertilizer in field-grown maize
2010
Riedell, Walter E.
Nitrogen (N)-fertilizer applications to field-grown maize may result in a dilution response whereby essential mineral-element concentrations in shoots would decrease as shoot-dry-matter accumulation increased. To investigate this, the effect of N-fertilizer treatments (no N or fertilizer rate based upon 5.3 or 8.5 t ha⁻¹ yield goal) on maize (Zea mays L.) shoot dry weight and shoot mineral concentrations (N, P, K, S, Mg, Ca, and Mn) at the sixth leaf (V6), twelfth leaf (V12), and tassel (VT) development stages were investigated in a 2-year study conducted at Brookings, South Dakota (USA). With increasing N-fertilizer application rates, shoot dry weight was greater and shoot P and K concentrations decreased. A possible explanation of this dilution response is that planting-time P and K fertilizers, which were applied in a band near the seed furrow, may have enhanced the uptake of P and K in a manner that was independent of N-fertilizer treatments. Increased shoot-dry-weight production due to the application of N fertilizers, if P and K uptake were similar across N-fertilizer treatments, would lead to decreased shoot P and K concentrations in N-sufficient compared with N-deficient plants. Conversely, N-fertilizer-induced increases in shoot dry weight were accompanied by increased shoot concentrations of N, Ca, and Mn. This synergistic response between dry-weight accumulation and shoot N concentration was present at all leaf developmental stages studied, while that for Ca was present only at VT. Thus, N fertilizer applications that increase shoot dry weight can affect the dilution and synergistic responses of specific mineral nutrients in maize shoots. Crop developmental stage as well as the location of these specific mineral nutrients in the soil profile might play important roles in mediating these responses.
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