Effects of temperature on mineralization and adsorption of exogenous amino acids and peptides in soil

An incubation test was conducted to study the effects of different temperature (1 ℃, 15 ℃, and 25 ℃) on the mineralization and adsorption of exogenous amino acid and peptide in the soils of horticultural production systems, including organic farming system (OS), transitional farming system (TS), and conventional farming system (CS). With the increase of incubation temperature, the mineralization of exogenous amino acids and peptides in test soils quickened. The mean half-life (D50) of Glu at 1 ℃, 15 ℃, and 25 ℃ was 13.3, 6.8, and 5.5 h, while the D50 of Glu-Phe was 29.7, 7.5, and 4.4 h, respectively. The adsorption rate of the exogenous amino acids and peptides was dependent on their concentrations and incubation temperature. The maximum adsorption rate (Vmax) and affinity (Km) of amino acids and the adsorption rate (Vh) of peptides were all increased with incubation temperature. In the range of 0-2.5 mmol·L-1, the adsorption of amino acids conformed to classical Michaelis-Menten equation, while that of peptides conformed to linear equation. The turnover rate and the Vmax, Km, and Vh values of exogenous amino acids and peptides generally followed the series OSTSCS. In summary, temperature had significant effects on the mineralization and adsorption of exogenous amino acids and peptides in test soils.