ISSN 1392-3196 / e-ISSN 2335-8947
Zemdirbyste-Agriculture, vol. 104, No. 2 (2017), p. 115–122
DOI  10.13080/z-a.2017.104.015

Empirical models of transformations of humic acids and humin in Umbric Albeluvisol Abruptic as influenced by liming



The research studied the changes in total carbon (C) content – carbon of humic acids (HA), and non-hydrolysable residue – humin (NR) in Umbric Albeluvisol Abruptic (umABap) under application of a wide range of doses (0.1–2.5 hydrolytic acidity (Hy), meq per 100 g of soil) of lime in the controlled conditions of a pot experiment. The trend of decreasing of total humus content in the soil was revealed only under application of the highest dose (2.5 Hy) of lime. A gradual decline in the proportion of humin and increase in the proportion of humic acids correspondingly to the doses of lime was observed. The correlation coefficient between humin and ƩHA was r = −0.49. Moderately negative correlation between the content of humin and humic acid 1 (HA1) “free” and bound with sesquioxides was found: r = −0.37; between humin and humic acid 2 (HA2), bound to calcium: r = −0.75. HA1 and HA2 fractions were not significantly correlated. The increase in the humus content of humic acid 3 (HA3) that is tightly bound with clay minerals and stable forms of sesquioxides was found only starting from the dose of lime corresponding to 0.9 Hy. At a dose of lime, equal to 2.5 Hy its content in humus exceeded the content of HA2. The hypothesis of the research suggesting that the source of replenishment of the portion of humic acids might be the organic substances of humin was proved. The empirical models of transformation of humic acid and humin as influenced by increasing doses of lime and in the process of its dissolution were developed. Optical densities of humic acids were presented.

Key words: fractionation, humic acid fractions, humin, hydrolytic acidity, liming.

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