Effect of Different Kinds of Humic and Fulvic Acids on the Release of Manganese from Calcareous Soils

Articles in Press

Document Type : Research Paper

Authors

1 Department of Soil Science, Faculty of Agriculture, University of Tehran, Karaj, Iran

2 Ph.D Graduate, Department of Soil Science and Engineering, Faculty of Agricultural Engineering and Technology, University of Tehran, Iran

3 Soil and Water Research Institute, Agricultural Research, Education, and Extension Organization, Karaj, Iran

Abstract

One of the limiting factors in crop yield in calcareous soils of arid and semi-arid regions is the deficiency of micronutrients in these soils. This study was conducted to examine the effects of various commercial humic acids (HAs) and fulvic acids (FAs) on the release of manganese (Mn) in 15 calcareous soils. The results indicated that the application of all five different HAs used in this study had no significant effect (P<0.05) on the release of Mn, but the effects of FAs varied in different soils, the majority of them resulted in a significant increase (P<0.05) in Mn release. In 20% of the soils, either three or all five FAs, and in 26.7 % of the soils, either two or four of the FAs resulted in a significant increase in Mn release. In one soil, none of the FAs were effective in increasing Mn release. Two FA samples, FA1 and FA5, were much more efficient in releasing Mn, indicating that the effectiveness or ability of the marketed or commercial FAs to release Mn, on an equal weight basis, is not the same and varies greatly among them. The difference was, to some extent, due to the ability of these humic substances to form strong (multidentate) complexes with Mn or act as a chelating agent. The results also indicated that effectiveness was dependent on soil characteristics, which were related to the binding strength of Mn with surface functional groups of soils and the solubility of Mn minerals in the soil.

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Iranian Journal of Soil and Water Research

Articles in Press, Accepted Manuscript
Available Online from 19 June 2024

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