Submitted to: Biology and Fertility of Soils
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/8/2003
Publication Date: 1/14/2004
Citation: Cecchi, A.M., Koskinen, W.C., Cheng, H.H., Haider, K. 2004. Sorption-desorption of phenolic acids as affected by soil properties. Biology and Fertility of Soils. 39:235-242. Interpretive Summary: Phenolic acids are exuded from plant roots into soil. They have been shown to reduce plant growth, water utilization, hydraulic conductivity, and nutrient uptake and therefore, are under much scrutiny for herbicidal purposes, such as allelopathic agents (natural herbicides) and as leads to development of new synthetic herbicides. The extent to which these effects occur is directly related to the amount of phenolic acid bioavailable to the root system. Therefore, understanding the bioavailability of these compounds in the soil is a key to managing allelopathic/herbicidal characteristics. The objective of this study was to characterize bioavailabilty of these chemicals through measurement of their sorption-desorption on a variety of soils. We found that sorption of the phenolic acids tested was very high and dependent on a variety of soil characteristics. We also found that sorption was irreversible for the aqueous desorption method used, indicating the possibility that the chemicals may be present in soils, yet unavailable to plants and soil microorganisms. Due to being biologically unavailable for uptake and breakdown, the chemicals may persist in the soil for long periods. Also, it is unlikely that the chemicals would be transported far from their point of origin, limiting their range of influence. These results are important for scientists to consider when evaluating phenolic acids as a potential basis for development of herbicides. These results will also aid in development of research designed to determine how these chemicals are able control weeds once they are exuded from plant roots, taking into account their extremely limited potential mobility.
Technical Abstract: Phenolic acids have been implicated in the process of allelopathy and are, therefore, of interest in plant management as a basis for new herbicide structures. Potential bioavailability of phenolic acids is controlled by sorption-desorption processes in soil. Sorption-desorption of p-coumaric acid (4-hydroxycinnamic acid), ferulic acid (3-methoxy-4-hydroxycinnamic acid), veratric acid (3,4-dimethoxybenzoic acid), vanillic acid (3-methoxy-4-hydroxybenzoic acid), and p-hydroxybenzoic acid (4-hydroxybenzoic acid) was characterized on soils with varying physicochemical properties. The phenolic acids sorbed quickly (<8 hr) and in high proportions to the amount applied (average 84% of applied was sorbed). Sorption was irreversible with the batch desorption method used (0.01 N CaCl2 extraction). Pretreatment of the soils to remove organic matter and free metal oxides from the soils decreased sorption, particularly in the soils with free oxides removed. Statistical analysis suggested that sorption of p-coumaric and ferulic acids was correlated with soil clay content and veratric acid with several soil factors. In contrast, no reliable relationship between soil characteristics and vanillic and p-hydroxybenzoic acid sorption was found. Sorption-desorption of the phenolic acids in soils appears to be a significant consideration in understanding allelopathic interactions and investigating new herbicidal leads.