| Abstrakt: |
Nitrogen fertilizer recommendations in humid regions have been primarily based on crop N requirements without regard for the variability in the N‐supplying capability of the soil. We found (reported in a separate article) that two previously proposed N availability indexes, 0.01MNaHCO3and boiling 0.01MCaCl2extractable N, were well correlated (r= 0.77 and 0.86, respectively; P < 0.01 for both) with the capability of eight Pennsylvania soils to supply N to field grown corn, (Zea maysL.). However, the time and expense required for these analyses may preclude their routine use by soil testing laboratories. In seeking ways to shorten and simplify the analyses, we found that the ultraviolet (UV) absorption by the 0.01MNaHCO3soil extract at 260 nm was as well correlated with the N‐supplying capability of the test soils (r= 0.865 P< 0.01) as the best of the previously evaluated extractable N indexes. This new method is as rapid, simple, and inexpensive as the methods currently used to measure availability of other essential nutrients in the soil. We also demonstrate how this method can be used to predict more accurately the fertilizer N needs for corn. |
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