## 3 Results and Discussion
Among commonly occurring amino acids, the following were not found in reference soils: cysteine and histidine. In irrigated soils, alanine, asparagic acid, glutamic acid, cysteine, and histidine were not identified. An interesting picture is observed regarding the content of a number of other amino acids, so from the group of aromatic amino acids, both in the reference and irrigated Light Calcisols, there is no histidine in the soil profile, and in irrigated soils, there is no asparagine or glutamic acid from the group of monoamine-dicarboxylic acids. Some decrease in amino acid content in irrigated soils is observed. The content of free amino acids in virgin Light Calcisols as a total mass averages 26.56 mg/kg. In soil horizons, they vary from 5.83 to 64.24 mg/kg. The relative distribution of free amino acids in soils is as follows: monoaminodicarboxylic acids (glycine, alanine, serine, threonine, methionine, valine, leucine, and isoleucine) 35.55-46.11%; monoaminodicarboxylic acids (asparagic acid, asparagine, glutamic acid,  
Figure 3: Soil organic carbon (SOC) stock in the 0–100 cm layer for different Calcisols. DCL—Dark Calcisol, TCL—Typical Calcisol, LCL—Light Calcisol. and glutamine) 35.53-45.04%; diaminmonocarboxylic (lysine and arginine) 3.6-9.65%; aromatic amino acids (phenylalanine, tyrosine, and tryptophan) 4.99-13.07%; and imino acids (proline) 2.62-4.43% of total amino acids. Figure 4: Relationship of profile distribution of total nitrogen (TN) and soil organic carbon (SOC) in reference and irrigated Calcisols. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Horizon** & **CHA 1** & **CFA 2** & \begin{tabular}{c} **CHA** \\ **CFA 2** \\ \end{tabular} & \
\begin{tabular}{c} **Horizon** \\ **CFA** \\ \end{tabular} & **CHA** & **CFA** &
\begin{tabular}{c} **CHA** \\ **CFA** \\ \end{tabular} \\ \hline \multicolumn{8}{c}{_Dark Calcisol_} \\ \hline \multicolumn{8}{c}{Reference} & \multicolumn{8}{c}{Irrigated} \\ \hline AU & 0.51 & 0.49 & 1.04 & PU & 0.40 & 0.42 & 0.95 \\ BCA & 0.31 & 0.30 & 1.03 & BCA & 0.29 & 0.34 & 0.85 \\ \hline \multicolumn{8}{c}{_Typical Calcisol_} \\ \hline \multicolumn{8}{c}{Reference} & \multicolumn{8}{c}{Irrigated} \\ \hline AJ & 0.24 & 0.26 & 0.92 & PJ & 0.28 & 0.35 & 0.80 \\ BCA & 0.09 & 0.10 & 0.90 & BCA & 0.10 & 0.14 & 0.71 \\ \hline \multicolumn{8}{c}{_Light Calcisol_} \\ \hline \multicolumn{8}{c}{Reference} & \multicolumn{8}{c}{Irrigated} \\ \hline AJ & 0.10 & 0.13 & 0.77 & PJ & 0.12 & 0.18 & 0.67 \\ BCA & 0.05 & 0.06 & 0.83 & BCA & 0.07 & 0.11 & 0.63 \\ \hline \end{tabular} \({}^{\dagger}\)Carbon of humic acids, 2 carbon of fulvic acids.  
\end{table} 
Table 1: Carbon of humic acids (CHA) and carbon of fulvic (CFA) acids (% to fine earth) and CHA/CFA ratios in soils investigated. Figure 5: Content of free carboxylic amino acids in Dark (**a**) and Light (**b**) Calcisol, mg/kg. Figure 6: Content of free amino acids in Dark Calcisol, mg/kg. Some decrease in amino acid content in irrigated soils is observed. The content of free amino acids in virgin Light Calcisols as a total mass averages 26.56 mg/kg. In soil horizons, they vary from 5.83 to 64.24 mg/kg. The relative distribution of free amino acids in soils is as follows: monoaminodicarboxylic acids (glycine, alanine, serine, threonine, methionine, valine, leucine, and isoleucine) 35.55-46.11%; monoaminidcarboxylic acids (asparagic acid, asparagine, glutamic acid, and glutamine) 35.53-45.04%; diaminmonocarboxylic (lysine and arginine) 3.6-9.65%; aromatic amino acids (phenylalanine, tyrosine, and tryptophan) 4.99-13.07%; and imino acids (proline) 2.62-4.43% of total amino acids. Increase in the number of amino acids, in particular arginine, which under the influence of the enzyme arginase in soils increases the synthesis of urea, can be noted as a positive factor. Between 14 and 20 amino acids were found in the Calcisols investigated. In virgin light gray soils, cysteine and histidine dominated.