New data have been obtained regarding the fractional composition of amino acid (AA) nitrogen and its reserves (0.45 to 1.6 t/ha) in carbonated chernozem of fodder crop rotations with 7 soles relative to humus reserves (0.79 to 2.16% ) and gross nitrogen (9.85 to 30.59%). Content of the hydrolyzed forms of nitrogen (43.73 to 74.6%) and the contribution of individual amino acids in the formation of amino acid nitrogen (0.22 to 11.07%) was determined. Nitrogen of 6 AA (alanine, aspartic acid, glycine, arginine, glutamic acid and serine) of the forage crop rotations made up to 67% of the total nitrogen of AA. The share of 9 AA in the formation of nitrogen reserves (lysine, leucine, proline, threonine, histidine, valine, isoleucine, cystine and phenylalanine) reached up to 30%. The smallest contribution in this process was brought by tyrosine, methionine and γ -aminobutyric acid. The obtained results show the superiority of celery soil in the formation of amino acid nitrogen fund (1.6 t/ha). The structural changes of the latter can be characterized analogically to the changes in the structure of microbial communities, which are usually observed in stressful situations.