Total phenolics soils

All total phenolic acid values in ferulic acid equivalence were determined by water-autoclave extraction and the Folin Cicoltaeu s phenol reagent approximately biweekly during the 1992 and 1993 experimental periods. Mean total phenolic acid for the upper 2.5 cm of the soil in 1992 were as follows plots without cover crops (reference plots) 41 1 rg/g soil (mean standard error), crimson clover plots 55 1 JLg/g soil, subterranean clover plots 58 1 p,g/g soil, rye plots 50 1 irg/g soil, and wheat plots 45 1 rg/g soil (Fig. 3.14 Blum et al. 1997). In 1993 soil total phenolic acid values for the upper 2.5 cm of the soil were higher than in 1992 (Fig. 3.14 Blum et al. 1997). The values for the April glyphosate desiccated plots were plots without cover crops (reference plots) 62 2 t,g/g soil, crimson clover plots 83 4 jtg/g soil, subterranean clover plots 83 3 t,g/g soil. 

At this point some comments regarding the modification of the soil physical and chemical environments by cover crops and weed seedling emergence appear appropriate. In spite of the fact that covariate, correlation and principle component analyses did not identify any significant relationships between seedling emergence and bulk soil physical and chemical characteristics (e.g., soil total phenolic acid. 

Total Phenolics and Phenolic Acids in Plants and Soils 155... 

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

Table VII. Concentration (ppm) of Total Herbicides, Total Phenols, and TCDD In 12 Soil Samples Collected July 1977 from the Herbicide Orange Storage Areas, Johnston Island and...

The effects of five phenolic compounds, catechol, protocatechuic, p-coumaric, p-hydroxybenzoic, ferulic acids and their mixture were studied on pH, organic matter, organic-nitrogen, total phenolic content and certain inorganic ions of forest mineral soils (Ae and B horizons). The A- and B-horizon soils, were amended with 104 M concentration of each phenolic compound and their mixture. In general, soil properties were affected by phenolics amendement. However, soils amended with catechol did not influence any of the soil characteristics. Contents of organic matter, nitrogen and phosphate were lower in soils amended with different phenolic compounds compared to the unamended control soil (Inderjit and Mallik, 1997). 

Total pmol/g soil of phenolic acid mixture... 

Thus the summed or average action of extracted available total phenolic acids in soils is just as important as understanding the action of available individual phenolic... 

There is, however, a caveat for estimating available total phenolic acid concentrations. The estimates of the total available fraction of phenolic acids in soil extracts represent a crude estimate of what actually occurs in soil, not only because of the range of efficiencies of extraction procedures but also because different phenolic acids at the same concentration generate different absorbances with Folin Ciocalteu s phenol reagent (Fig. 3.7 Blum et al. 1991). In addition soil extracts also contain compounds, other than phenolic acids, that react with (i.e., reduce) the Folin Ciocalteu s phenol reagent (McAllister 1969 Box 1983). The assumption, therefore, was that available total phenolic acid values based on the Folin Ciocalteu s phenol reagent expressed as ferulic acid equivalence were relative values that were consistently related to the acmal total available phenolic acids (hereafter just called total phenolic acid) present in soil extracts. The extraction and quantification by HPLC analysis of available individual phenolic acids in soil do not have these particular problems. 

So what were the concentrations of phenolic acids in the Cecil A soil wheat stubble (Triticum aestivum L. Coker 916 )/soybean (Glycine maxL. Deltapine417 ) systems Subsamples taken from wheat stubble/soybean (no-till), wheat stubble tilled under/soybean (conventional-till), and fallow/soybean soil (conventional-till) cores were extracted by the water-autoclave procedure and analyzed for 7 common phenolic acids (ferulic, caffeic, p-coumaric, p-hydroxybenzoic, sinapic, syringinc, and vanillic) and total phenolic acid (Blum et al. 1991). With minor exception, individual phenolic acids were correlated with each other, with the sum of the 7 phenolic acids identified by HPLC analysis, and total phenolic acid as determined by the Folin Ciocalteu s phenol reagent method. 

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