Cecil B, soil

Fig. 2.22 Concentrations of p-coumaric acid and metMonine (a), and p-coumaric acid and glucose (b) required to inhibit dry weight of morningglory seedlings growing in Portsmouth B and Cecil B soils, respectively, by 10-50%. Figures adapted/repUcated from Blum et al. (1993) (a) and Pue et al. (1995) (b). Plenum Publishing Corporation, figuresused with permission of Springer Science and Business Media...

One hundred days after the addition of 1,000 p.g/g (approximately 5 timol/g soil) ferulic acid to sterile Cecil soil samples, water, neutral EDTA, and water-autoclave extractions recovered 28% (277 tig/g), 37% (373 tig/g), and 32% (322 p.g/g) of the ferulic acid added, respectively, from Cecil A soil samples (3.7% organic matter) and 17% (167 tig/g), 52% (524 tig/g), and 30% (304 p.g/g) of the ferulic acid added, respectively, from Cecil B soil samples (0.2% organic matter Blum et al. 1992). The recovery of femlic acid from soil by neutral EDTA extraction was thus more effective than the water-autoclave extraction. 

For soil samples that had been inoculated with microorganisms 70 days after the addition of ferulic acid, recovery was reduced to less than 2% 30 days after soil samples were inoculated (for Cecil A soil samples 0, 4, and 20 p.g/g were recovered, respectively for Cecil B soil samples 0, 0.4, and 4 p.g/g were recovered, respectively). More of the ferulic acid recovered by neutral EDTA was available to soil microbes. This indicated that there was not only a quantitative difference but also a qualitative difference in the fractions of sorbed ferulic acid recovered by the two extraction procedures. By fractions I am referring to ferulic acids bound by different kinds and strengths of bonds to soil particles (see Section 2.4.3.2). 

Reversible sorption of phenolic acids by soils may provide some protection to phenolic acids from microbial degradation. In the absence of microbes, reversible sorption 35 days after addition of 0.5-3 mu mol/g of ferulic acid or p-coumaric acid was 8-14% in Cecil A(p) horizon and 31-38% in Cecil B-t horizon soil materials. The reversibly sorbed/solution ratios (r/s) for ferulic acid or p-coumaric acid ranged from 0.12 to 0.25 in A(p) and 0.65 to 0.85 in B-t horizon soil materials. When microbes were introduced, the r/s ratio for both the A(p) and B-t horizon soil materials increased over time up to 5 and 2, respectively, thereby indicating a more rapid utilization of solution phenolic acids over reversibly sorbed phenolic acids. The increase in r/s ratio and the overall microbial utilization of ferulic acid and/or p-coumaric acid were much more rapid in A(p) than in B-t horizon soil materials. Reversible sorption, however, provided protection of phenolic acids from microbial utilization for only very short periods of time. Differential soil fixation, microbial production of benzoic acids (e.g., vanillic acid and p-hydroxybenzoic acid) from cinnamic acids (e.g., ferulic acid and p-coumaric acid, respectively), and the subsequent differential utilization of cinnamic and benzoic acids by soil microbes indicated that these processes can substantially influence the magnitude and duration of the phytoxicity of individual phenolic acids (Blum, 1998). 

Recovery of phenolic acids by NaOH from amended soil samples was equal to or greater than those recovered from non-amended soil samples. The difference (minus approximately 0.01 p,mol/g soil) in recovery between amended and non-amended phenolic acid soils represented a portion of the amended phenolic acids (i.e., 1 M NaOH extractable) that had been irreversibly sorbed during the equilibration and/or incubation periods. Values for 1 M NaOH extractable phenolic acids from non-amended soils were < 0.0017 xmol/g soil for Cecil B (0.2% organic matter) soil samples and ranged from 0.013 xmol/g soil for ferulic acid to 0.073 p,mol/g soil for p-coumaric acid in the Cecil A (3.7% organic matter) soil samples. Differences between amended and non-amended soils ranged from 0 xmol/g soil for p-coumaric acid to 0.024 p,mol/g soil for ferulic acid in Cecil A soil samples and 0.013 p,mol/g... 

Fig. 2.15 Recovery, over time, of ferulic (FER) acid (a P > 0.89) and vanillic (VAN) add (b) from sterile Cecil A and B soils by 0.25 M EDTA (pH 7) or water. Phenolic add added at time zero was 2.5 xmol/g soil. Standard error bars for (b) are smaller than the symbol representing the mean, a based on regressions and b based on data points of two figures from Blum et al. (1994). Plenum Publishing Corporation, regressions and data used with permission of Springer Sdence and Business Media...

Fig. 2.18 Percent femUc add tind vanillic acid reversibly sorbed and fixed (irreversibly sorbed) by sterile Cecil A (a) and B (b) soils over time. Percentages based on 1-3 jtmol/g soil added at time zero. Figures based on data from Blum et al. (1999b). CRC Press LLT, data used with permission of Taylor Francis Ltd, http //www.tandf.co.uk/journals. Original sources of data Blum (1997, 1998) and Blum et al. (1994)...

Fig. 2.26 Recoveries of g-coumaric add from the bottom of Cecil A soil columns in the presence of cucumber seedlings and microbes (a), in the absence of microbes and seedlings (b), and in the presence of microbes but absence of seedlings (c). For (a), approximately 25, 50 or 95 [xg/ml of p-coumaric acid in 25% Hoagland s nutrient solution was applied to the columns at a rate of 2-3.5 ml/h. For (b) and (c), 41 and 54 jjig/ml, respectively, of p-coumaric acid in different nutrient solution concentrations (0-50%) was apphed to columns at the same rate as in (a). Figures reproduced from Blum et al. (1999a). Cddiz Univ Press, Puerto Real. Figures used with permission of Servicio de Publicaciones Universidad De Cadiz...

Fig. 2.27 The changes in xmol/g soil / -coumaric acid (a), soil water (g/150 g soil) (b), and mM p-coumaric acid (c) for cup systems with 12-13 day-old cucumber seedlings and Cecil A soil. Systems were treated with 1 p.mol/g soil p-coumaric acid and 20 or 25 g water/150 g soil. Absence of error bars indicates that error bars are smaller than the symbols representing the mean. Figures reproduced from Blum and Gerig (2006). Figures used with permission of Springer Science and Business Media...

In conclusion, the water-autoclave extraction procedure when compared to the EDTA extraction procedure underestimated the total available ferulic acid in the soil by roughly 5% for Cecil A and 22% for Cecil B. In addition to the quantitative difference there also appeared to be a difference in the types of the sorbed ferulic acid recovered. The water-autoclave-procedure recovered some irreversibly sorbed phenolic acids from Cecil A soil since only 55% of the sorbed phenolic acid recovered was utilized by microbes. This difference should not be surprising since the physical and chemical processes of the two extraction procedures, i.e., chelation vs. 

Fig. 3.12 The number of pigweed seedlings in cover crop and reference plots for the 1993 experimental period in no-till Cecil A soil. Glyphosate desiccation of cover crops occurred on April 29 (a) and May 10 (b). Where C equals crimson, S equals subterranean and reference equals no-cover crop plots. Figures reproduced from Blum et al. (1997). Henry A Wallace Institute for Alternative Agriculture Inc, figures used with permission of Cambridge University Press...

Fig. 3.17 Average number of morningglory, pigweed, and prickly sida seedlings in no-tiU Cecil A soil field plots for two experimented periods [(a) 1996 and (b) 1997] with the following 5 treatments 1. no cover crop (reference), 2. cut wheat shoots on surface (s only), 3. wheat roots left in place but shoots cut and removed (r only), 4. wheat shoots and roots left in place, but shoots cut (s+r cut), and 5. wheat shoots and roots left in place, but shoots not cut (s+r not cut). The absence of standard error bars indicates that the error bars are too small to be visible. Figures based on data from Blum et al. (2002). Data used with permission of International Allelopathy Foundation...

Fig. 3.20 Effects of wheat shoot (a ranged from 0.54 to 0.80) tind sunflower leaf (b r ranged from 0.55 to 0.77) tissues incorporated into Cecil A soil on percent inhibition of absolute rates of leaf expansion of cucumber seedlings over time. Kgures based on regressions from Staman et al. (2001). Plenum Publishing Corporation, regressions used with permission of Springer Science and Business Media...

Recovery of ferulic acid by various extraction procedures from sterile soils 90 days after ferulic acid solutions (1,000 mg/kg soil, pH 6.0) were added to soils. Soil-ferulic acid mixtures were stored in the dark at room temperature. LSDo.05 for Cecil A and B and Portsmouth A and B soils were 28.70, 44.15,40.69, and 28.66, respectively. Meaning of the abbreviations and details for extraction procedures are provided in Table 2.3. Figure based on data from Dalton et al. (1987). Data used with permission of Soil Science... 

Effects of total phenolic acid composed of a 4-equal-molar mixture of p-coumaric acid, ferulic acid, p-hydroxybenzoic acid, and vanillic acid on absolute rates of leaf expansion (cm /day r = 0.44) of 12 day-old cucumber seedlings and microbial populations (CFU/g soil r = 0.49) that can utilize phenolic acids as a sole carbon source in Cecil A soil (a). Relationships between phenolic acid-utilizing microbes (CFU, colony-forming units) and percent inhibition of absolute rates of leaf expansion for cucumber seedlings are presented in b. Values for (b) were calculated from values in (a). Figures based on regressions from Blum et al. (2000). 

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