Nitrogen

Abstract

The total nitrogen (N) content of a plant or one of its parts is an important physiological measurement, a parameter used to evaluate the plant's nutritional status. Kjeldahl digestion is the most frequently used analytical procedure for this N determination, a method developed over 100 years ago. The procedure may be defined in terms of the sample aliquot (micro, semimicro or macro), and by the method to assay the generated ammonium whether by acidimetric titration, colorimetry or by means of an ammonia‐sensing electrode. The obtained Kjeldahl N result will be affected whether nitrate is recovered, what catalyst is used, the digestion temperature and the length of time following clearing. In addition, sample particle size, amount of sample assayed and the digestion apparatus will contribute to the precision of the determination. All of these factors must be known if the determined Kjeldahl N content is to have significant value.

Key words:

• Plant N
• nitrate‐N
• ammonium‐N