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A simple model of pH in slurry

Published online by Cambridge University Press:  27 March 2009

S. G. Sommer  and
S. Husted
S. G. Sommer
Affiliation:
The Danish Institute of Plant and Soil Science, Department of Soil Science, Research Centre Foulum, PO Box 23, DK-8830 Tjele, Denmark
S. Husted
Affiliation:
The Danish Institute of Plant and Soil Science, Department of Soil Science, Research Centre Foulum, PO Box 23, DK-8830 Tjele, Denmark
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Summary

Ammonia volatilization from stored slurry or surface-applied slurry in the field is strongly affected by pH. Thus a simple, iterative model was developed to predict pH changes in slurry. Concentrations of NH4+/NH3, CO2/HCO3-/CO32- and volatile fatty acids were input data to the model. The model was validated by titrating 17 slurry samples collected from four cattle farms, seven pig farms and three biogas plants. Predictions of pH agreed well for 14 slurries with titration data in the pH interval from 4 to 10. Simulations indicated that microbial degradation of VFA to methane and carbon dioxide resulted in a pH increase if the carbon dioxide produced was lost to the atmosphere. There was little change in pH if the produced carbon dioxide dissolved in the slurry.

Type
Crops and Soils
Information
The Journal of Agricultural Science , Volume 124 , Issue 3 , June 1995 , pp. 447 - 453
Copyright
Copyright © Cambridge University Press 1995

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