Chlorophyll-type compounds in soil

Summary

The degradation of chlorophyll-type compounds (chlorophyll and its derivatives) in soil were followed by spectrophotometric and chromatographic techniques to find how closely they represent the bulk of plant material in soil. Tissue enzymes rapidly decomposed chlorophyll in chopped plant material mixed with soil, and decomposition was much slower in material in which the enzymes had been inactivated. This slow decomposition is by micro-organisms which seem to be the important cause of chlorophyll degradation in soil.

Micro-organisms decomposed both chlorophyllsa andb in two to four months in field soils; chlorophylla was attacked most. Of the chlorophyll-type compounds, pheophytin, the most closely related derivative of chlorophyll, resisted decomposition largest; chlorophyllide and pehophorbide were found rarely in soil and never in large amounts.

Microbiological decomposition increased with increasing moisture content of soil, was fastest at 50 to 60 per cent of the water-holding capacity. Decomposition slowed with increasing soil acidity and was very slow at pH below 4.0. Raising the temperature from 5° to 25°C increased the rate of degradation Neither the species nor quantity of plant material had much effect on the rate of decomposition.