Comparison of the effects of conventional organic amendments and biochar on the chemical, physical and microbial properties of coal fly ash as a plant growth medium |
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Authors: | O N Belyaeva and R J Haynes |
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Abstract: | The bulk of fly ash (an inorganic waste of coal-fired power generation) produced is deposited in disposal areas where it needs
to be revegetated. The effects of addition of three conventional organic amendments (biosolids, poultry manure, green waste
compost), or poultry manure-derived biochar, to coal fly ash (at two rates) on some key chemical, physical and microbial properties
and on growth of Rhodes grass (Chloris gayana) was studied in a laboratory incubation/greenhouse study. Addition of all amendments, including biochar, increased concentrations
of extractable Mg, K, Na and P and CEC(pH 7.0). Additions of poultry manure, and particularly biosolids, also greatly increased levels of extractable NH4
+ and NO3
−-N. Addition of biosolids, green waste compost and biochar resulted in a decrease in macroporosity, a concomitant increase
in mesoporosity and, at the high rate of addition, an increase in available water-holding capacity. Basal respiration was
very low in fly ash and was increased by addition of all amendments; metabolic quotient was markedly greater in control than
amended treatments. Biosolids, poultry manure and green waste compost additions all increased microbial biomass C. Growth
of Rhodes grass was extremely low under unfertilized conditions in control, biochar and, to a lesser extent, green waste compost
treatments but addition of poultry manure and the lower rate of biosolids resulted in large increases in yields. Although
biochar additions increased extractable Ca, K, P, Cu, Zn and Mn, CEC, mesoporosity and water-holding capacity, they had a
little or no stimulatory effect on the size of the soil microbial community, N fertility or plant growth. This was attributable
to the lack of metabolisable C and an insignificant N-supplying capacity. |
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