Stickstoffverbindungen in Böden und ihre Beziehung zur Humusdynamik. <i>2. Mitteilung: Zur Bestimmung und Zuordnung des Amidstickstoffs</i>

Abstract

Nitrogen compounds in soils and their relation to humus dynamics. 2. Communication: On the determination and attachment of amide‐nitrogen The amide‐nitrogen fraction in soils – so far very insufficiently defined – has been determined in the hydrolysates of 12 different soil samples. The proposed procedure allows to split this amide‐nitrogen fraction into two better befined N‐fractions, namely: real amide‐N (EAN) and pseudo‐amide‐N (PAN). This splitting is based on. 1.) a detailed N‐fractionation, especially a quantitation of aspartic acid + glutamic acid (AG) and ammonia in the hydrolysate, 2.) on the fact, that pure proteins and „soil proteins”︁ do not significantly differ in terms of their amino acid composition (average basis per mol protein) and deductive hereupon 3.) on the assumption, that the calculated NH 4 /AG‐ ratio of 0,5 from pure proteins can be transferred to „soil proteins”︁. Methodically the real amide‐N (EAN) and the pseudo‐amide‐N (PAN) are determined as follows: After quantitation of aspartic acid + glutamic acid (AG) in the soil hydrolysate EAN can be calculated by the equation: EAN = (AG) X 0,5. PAN amounts to the difference between Ammonia of the hydrolysate and EAN. For the 12 soil samples the PAN/EAN‐ratios are in the range 1,5–11,7.