One Possible Approach To Providing The Necessary Data To Test The Hypothesis

A range of concentrations of individual phenolic acids, mixtures of phenolic acids, or organic mixture including phenolic acids plus or minus nutrients and water plus or minus nutrients (control) could be added in solution form to soil surfaces in the field by direct applications or drip irrigation. However, surface applications of such solutions to field soil without some confinement are not advisable. The insertion of pipes into the soil (i.e., open ended soil cores) would be an effective way to eliminate horizontal movement and at the same time provide better phenolic acid distribution throughout the soil column. Such soil columns could also be brought to the laboratory, sterilized, and then used to determine soil sorption.13 Sufficient amounts or rates of solutions should be added for gravitational water to reach the bottom of the columns. Since soil columns will function as chromatographic columns, sufficient amounts and concentrations should also be used to obtain the desirable depth of phenolic acid penetration. The depth of penetration could be determined by subsampling of the columns or by the use of lysimeters at various depths. There is an additional benefit to the use of soil columns: seedlings could be planted into the soil cores, providing a means of regulating phenolic acid contact with roots. A laboratory version of this system has been used and described by Blum et al.3

Phenolic acids from lysimeters and/or extracted from the soil within the cores by water or EDTA could be analyzed by a high-performance liquid chromatography to determine transformation products and the rates of disappearance of available

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(free and reversibly sorbed) phenolic acids. ' Soil and rhizosphere microbial populations that can utilize phenolic acids as a carbon source could be determined by the plate-dilution frequency technique24 using appropriate selective media

containing phenolic acids as the sole carbon source. ' ' Observed phytotoxicity could be determined by monitoring leaf expansion of an appropriate species, for example, since that can be done nondestructively.4 The relationships between soil and rhizosphere phenolic acid utilizing microorganisms and observed phytotoxicity could thus be determined for these core systems using the approach described by Blum et al.9

Growing Soilless

Growing Soilless

This is an easy-to-follow, step-by-step guide to growing organic, healthy vegetable, herbs and house plants without soil. Clearly illustrated with black and white line drawings, the book covers every aspect of home hydroponic gardening.

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