MICROBIAL ACTIVITY IN BLOCKING COMPOSTS 4. FURTHER STUDIES ON THE DEGRADATION OF UREAFORMALDEHYDE

Microbial activity in blocking composts containing ureaformaldehyde (UF) was monitored by direct plate counts, measurement of CO₂ evolution and by assessment of ATP concentrations.
Nutrient concentrations in media were also determined.
These parameters were monitored in:

1. sterilised UF containing compost ‘inoculated’ with stored blocking compost which had contained UF

2. unsterilised UF containing compost ‘inoculated’ with stored blocking compost which had contained UF

3. unsterilised UF containing compost.

Concentrations of ammoniacal and nitrate nitrogen rose in (i) during the second week of the experiment and continued to rise indicating that the release of nitrogen from UF was rapid.
The rate of nitrogen release was greatest in compost (i) and least in compost (iii). Clearly the addition of ‘stored’ blocking compost containing the micro-organisms responsible for UF breakdown had indeed induced rapid UF breakdown.
The rate of oxidation of ammoniacal nitrogen to nitrate nitrogen was also faster in ‘inoculated’ composts.
Oxidation of ammoniacal nitrogen also corresponded with a drop in pH and higher calcium and magnesium concentrations.
This supports the proposal that the release of H⁺ ions during nitrification lowers the pH causing solubilisation of the carbonate in dolomitic limestone and release of free Ca⁺⁺ and Mg⁺⁺ ions.

Evolution of CO₂ was highest in compost (i), and ATP concentrations rose rapidly in this compost 1–6 days from the start of the experiment.
Finally, numbers of fungi and bacteria, initially low in compost (i) compared to (ii) and (iii), increased markedly 2–5 days from the start of the experiment.

Symposium on Nutrition, Growing Techniques and Plant Substrates

C.P. Turner, W.R. Carlile

https://doi.org/10.17660/ActaHortic.1986.178.41