A comparison of analytical methods for nitrogen analysis in plant tissues

Abstract

Automated Dumas methods could replace Kjeldahl digestions for the analysis of nitrogen (N), but few comparisons of these methods for plant tissue are available. Because N nutrition usually affects tissue levels of N, the influence of analytical method (Dumas and a modified micro‐Kjeldahl without salicylic acid pre‐treatment) on N determination in leaves and petioles of ‘Shogoin’ turnips grown under different N regimes was investigated. Dumas‐ and Kjeldahl‐N ranged from 1.31 to 6.70% and 1.22 to 5.77% in leaves and petioles, respectively, and Dumas‐N was significantly (p<0.01) higher than Kjeldahl‐N. This resulted in a tendency to overrate N status when available thresholds developed with Kjeldahl‐N values were use with Dumas‐N data. However, for turnip, Kjeldahl‐N could be estimated from Dumas‐N in the 1–6% range as: Kjeldahl‐N = ‐0.015 ^(p=0.82) + 0.858 ^(p<0.001) Dumas‐N (p<0.01, R² = 0.98) , and developing new interpretative data for Dumas N was not necessary.

Notes

Present address: Department of Horticulture, 101 Funchess Hall, Auburn University, AL 36849–5408.

Present address: Micro‐Macro International, Inc., 108 Paradise Blvd., Suite 108, Athens, GA 30607.