Akbar Hassani
Soil Science department, Faculty of agriculture, University of Zanjan

Abstract
Chemical modification of humic substances used for better understanding of the chemical structure of the compounds and their effects on the plants growth. The purpose of this study was to investigate the structural differences between simple humic acid and bioactive humic acid and to compare their effects on root growth of maize to be used in organic farming. The results showed that the number of surface functional groups in bioactive humic acid is 31% more than that in simple humic acid and C/N ratio was half of that in bioactive HA. Maize seedlings treated with different concentrations of humic acid showed that the best concentration of both HA and bioactive HA to grow maize root is 60 mg.L-1. Mitotic sites of roots treated with HA and bioactive HA was 2.62 and 3.16 fold compared to control respectively.

Keywords: bioactive humic acid, surface functional groups, Maize, growth stimulator

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