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United States Department of Agriculture

Agricultural Research Service

Title: Transformations of Plants to Humic Substances

Authors
item Byrne, Corinna - LIMERICK UNIV
item Hayes, Mhb - LIMERICK UNIV
item Clapp, Charles

Submitted to: Proceedings of the Brazilian Socity of Humic Substances
Publication Type: Proceedings
Publication Acceptance Date: June 15, 2004
Publication Date: July 25, 2004
Citation: Byrne, C.M., Hayes, M., Clapp, C.E. 2004. Transformations of plants to humic substances. Proceedings of the Brazilian Socity of Humic Substances. p. 247-250.

Interpretive Summary: Additions of corn stover have been shown to compensate for the losses of soil carbon when corn is grown in continuous annual cropping in Ireland. Our objective was to observe how corn is transformed in the soil over time, and to get an awareness of the formation with time of humification products. A calcareous sandy soil medium was taken at a County Clare sand dune golf course. Grass is the climax vegetation. Corn was the amendment chosen because it is a plant enriched in carbon-13, a stable tracer isotope. The sand was free from organic carbon. Thus changes in the carbon isotope values of the extracts would indicate carbon inputs from non-corn sources during the course of the humification processes. In this study resin techniques were used for the fractionation of humic substances from the sand mixture. During the incubation no humic substances were formed that were soluble at pH 7, but some humic and fulvic acids were soluble at higher pH values. The results of these experiments are being shared with turfgrass scientists and horticultural specialists to provide information on supplying trace metals to grasses.

Technical Abstract: This study was designed to follow the transformations that take place in soil organic amendments in the course of humification. Our objective was to observe how corn is transformed in the soil over time, and to get an awareness of the formation with time of humification products. The results represent transformations that took place in the first year of incubation of corn silage in calcareous organic free sand. During the incubation time no humic substances were formed that were brought into solution at pH 7 and attention was focused on the humic acids and fulvic acids that were extracted at pH 10.6 and 12.6. In most studies of soil humic substances attempts are not made to fractionate on the basis of charge density differences, and thus specific components that are soluble in the pH range 7-10 and 10-12 are missed. The present study will be continued for a further two years and it will then be possible to observe the changes that take place in the materials that are now isolated at pH 10.6, but will be further oxidized to humic substances soluble at pH 7.

Last Modified: 8/21/2014
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