METHOD FOR QUICKLY DETERMINING NITROGEN IN PLANTS, AND SOLUBLE NITROGEN AS A MEASURE OF THE NITROGEN AVAILABLE FOR ANABOLIC PROCESSES

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Abstract
Total N in plant material is detd. by oxidizing the N to HNO3 by heating a small sample with NaClO3 and H2SO4 in the presence of a reflux condensor. The HNO3 acid in strong H2SO4 is detd. by means of phenol-disulfonic acid. Chlorides do not interfere when the phenoldisulfonic acid is added to the strong H2SO4 solution containing the HNO3. The procedure requires 10-15 min. and very simple apparatus, checking well with the Kjeldahl method. The presence of water in green plant material does not interfere. The N in a 2% acetic extract of green plants was detd. by a method using NaClO3, fuming H2SO4 and phenoldi-sulfonic acid. The method may be carried out in a test tube without heat, requiring only 5 min. This makes it practical for field testing. All N in solution is changed to nitrate and all organic matter destroyed. The N thus detd. seems to be an accurate measure of the N available for anabolic processes as indicated by the results of determinations on beans, tomatoes, cabbage and peaches presented along with yields and growth responses.

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