ISHS Acta Horticulturae 172: Composts as Horticultural Substrates
SOLUBLE SALT CONCENTRATIONS AND CHEMICAL EQUILIBRIA IN WATER EXTRACTS FROM TOWN REFUSE COMPOSTS DURING COMPOSTING PERIOD |
| Authors: | S. CHARPENTIER, F. VASSOUT |
| Abstract:
High soluble salt contents were always a limiting factor of the use of domestic waste in the making of horticultural substrates. Main cations and anions of water extracts from two town refuse composts were analysed regularly during the composting period. One heap was held under shelter and the other exposed to the elements to study leaching effects on the liquid phase. The results indicated that conductivity was high from the beginning and that its variations remained weak. Levels of sodium and potassium cations and chloride and sulfate anions, always important and of equal size accounted for 50 to 80 per cent of the extract conductivity. Exposition of the heap to the elements might have a notable effect on the leaching of those components (from 10 to about 25 per cent). Other species like ammonia, Ca, and species constituting alcalinity contributed temporarily to high levels of conductivity. Those elements which take part in reactions of transformation and phase change had contents which varied considerably during the composting period. The computation of ion activity products agreed with the precipitation of Ca and Mg salts within the heap; a part of these salts were dissolved again with decreasing pH during nitrification. | |
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