Phenolic acids in soils

T. Makino, Y. Takahashi, Y. Sakurai. and M. Nanzyo, Influence of soil chemical properties on adsorption and oxidation of phenolic acids in soil suspension. Soil Sci. Plant Nittr. 42 U1 (1996). 

DETERMINATION OF TOTAL PHENOLICS AND PHENOLIC ACIDS IN SOILS... 

Hennequin, J. R. and Juste, C. (1967). Presence of free phenolic acids in soil Study of their influence on germination and growth of plants. Annual Agronomy 18 545-... 

DAO Sorption and Mineralization of Plant Phenolic Acids in Soil... 

There is some confusion in the literature as to when it is appropriate to apply the term allelochemical to phenolic acids. Since phenolic acids and their derivatives are found essentially in all terrestrial soils, it should be understood that the presence of phenolic acids in soil does not automatically imply that these phenolic acids are functionally allelochemicals. In theory, phenolic acids in soils, depending on their chemical state, concentrations, and the organisms involved, can have no effect, a stimulatory effect, or an inhibitory effect on any given plant or microbial process. For phenolic acids in the soil to be classified as allelochemicals requires that a) the phenolic acids are in an active form (e.g., free and protonated), b) they are involved in chemically mediated plant, microbe, or plant/microbial interactions and c) the concentrations of the active forms in the soil solution are sufficient to modify plant or microbial behavior, either in a positive or negative manner.8,49 However, changes in microbial behaviour associated with the utilization of phenolic acids as a carbon or energy source would not qualify as an allelopathic response. 

Rates of transformation and/or disappearance of phenolic acids in soil solutions have also been determined under a variety of circumstances and in various soils.2 22 23 31 42,44 In general, there is a rapid initial transformation (e.g., loss of the carboxylic acid group) of phenolic acids. For example, 90% of the carboxylic acid carbon of p-hydroxybenzoic acid, syringic acid, and vanillic acid was lost within 1 week.22 Losses of other side chain carbons or ring carbons, however, took... 

Blum, U. and Shafer, S. R. 1988. Microbial populations and phenolic acids in soil. Soil Biol. Biochem. 20, 793-800... 

Dalton, B. R., 1999. The occurrence and behavior of plant phenolic acids in soil environments and their potential involvement in allelochemical interference interactions Methodological limitations in establishing conclusive proof of allelopathy. In Inderjit, Dakshini, K. M. M., and Foy, C. L., (Eds.), Principles and Practices in Plant Ecology Allelochemical Interactions, CRC Press, Boca Raton, FL, 57-74... 

Dalton, B. R., Blum, U. and Weed, S. B., 1989. Plant phenolic acids in soils Sorption of ferulic acid by soil and soil components sterilized by different techniques. Soil Biol. Biochem. 21, 1011-1018... 

Dao, T. H., 1987. Sorption and mineralization of phenolic acids in soil. In Waller, G. R., (Ed.), Allelochemicals Role in Agriculture and Forestry. ACS Symposium Series No. 330. American Chemical Society, Washington D.C., 358-370... 

Hartley, R. D. and Whitehead, D. C., 1985. Phenolic acids in soils and their influence on plant growth and soil microbial processes. In Vaughan, D. and Malcolm, R. E., (Eds.), Soil Organic Matter and Biological Activity. Martinus Nijhoff. Dr. W. Junk Publishers, Dordrech, Netherlands, 109 -149... 

To determine phenolic acids in soil, samples were snbjected to LEE with 0.1 M NaOH for 16 h, centrifngation, filtration and pH adjnstment. End analysis was by RP-HPLC on a C18 column with UVD at 280 nm. Recoveries were as follows p-hydroxybenzoic acid 123%, vanillic acid (38) 83%, syringic acid (70) 66%, conmaric acid (26) 100%, fernlic acid (69) 58% and caffeic acid (25) 0%. LOD was 0.5 ppm for the derivatives of benzoic acid and 1 ppm for those of cinnamic acid, excepting 25 that conld not be detected by this method . 

Historically, simple phenolic acids have been the most frequently identified allelopathic agents (see literature reviews by Rice 1974, 1979, 1983, 1984, 1986). One would assume this was partly because of the fact that the necessary technology to isolate, identify, and quantify phenolic acids, even though crude in the early days, was readily available to most researchers. Furthermore, simple phenolic acids, such as the benzoic acid and cinnamic acid derivatives serve a variety of plant and ecosystem functions and are widespread in higher plants (Fig. 2.4 Bates-Smith 1956 Harborne 1982,1990 Goodwin and Mercer 1983 Siqueira et al. 1991). The ubiquitous distribution in nature and their apparent rapid turnover rates in soils, however, have lead to some controversy as to the importance of phenolic acids in plant-plant allelopathic interactions (Schmidt 1988 Schmidt and Ley 1999 Blum 2004, 2006). Finally, the behavior of phenolic acids in soil systems are somewhat similar to the behavior of a whole host of other organic acids (e.g., acetic acid, butyric acid, citric acid, formic acid, fiimaric acid, lactic acid, malonic acid, tannic acids and tartaric... 

A range of extractants and extraction procedures has been used to extract phenolic acids from soil (Dalton 1999). Many of these extractants and extraction procedures, however, recover phenolic acids that are not directly involved in plant-plant allelopathic interactions (e.g., phenolic acids sorbed in the recalcitrant organic matter). Thus considerable efforts were made to identify extraction procedures that would provide reasonable estimates of available phenolic acids ( free phenolic acids in soil solutions and reversibly sorbed phenolic acids on soil particles) in soils (Dalton et al. 1983, 1987, 1989a, b Blum et al. 1994 Blum 1997 Dalton 1999). 

When phenolic acids enter the soil environment they are reversibly and irreversibly sorbed to soil particles, polymerized, oxidized, reduced, leached, utilized by microbes, and taken up by roots. Rates for these various processes are highly variable and depend on soil type, biotic and physicochemical soil environmenL types and mixtures of phenohc acids in or added to soils, and time, among others. To eliminate the effects of soil microbes, soils may be autoclaved. Concentrations of individual available phenolic acids in soils at a given point in time may be estimated by extracting soils with appropriate extractants and HPLC analysis. Based on our soils, we recommend water for estimating soil solution concentrations and neutral EDTA for soil solution and reversibly sorbed phenolic acid concentrations. However, the effectiveness of neutral EDTA in recovering available phenolic acids in all other soils should not be assumed. Reversibly sorbed phenolic acids increased or decreased as soil solution concentrations and multivalent cations increased or decreased, respectively. 

Effects of Seedling-Microbe-Soil Systems on the Available Concentrations of Phenolic Acids in Soil Solutions... 

Blum U, Rebbeck J (1989) The inhibition and recovery of cucumber roots given multiple treatments of femhc acid in nutrient culture. J Chem Ecol 15 917-928 Blum U, Shafer SR (1988) Microbial populations and phenolic acids in soils. Soil Biol Biochem... 

Dalton BR, Blum U, Weed SB (1989a) Plant phenolic acids in soils sorption of femlic add by soil and soil components sterihzed by different techniques. Soil Biol Biochem 21 1011-1018 Dalton BR, Blum U, Weed SB (1989b) Differential sorption of exogenously applied feniUc, p-coumaric,p-hydroxybenzoic, and vanillic acids in soil. Soil Sci Soc Am J 53 757-762 Dalton BR, Weed SB, Blum U (1987) Plant phenolic acids in soils a comparison of extraction procedures. Soil Sci Soc Am J 51 1515-1521... 

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