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Effect of Feedstocks on the Composting Process and Finished Products L.
R. Cooperband, A. G. Stone, M. R. Fryda and J. L. Ravet Combining waste streams as feedstocks for composting may
affect the compost process, duration to maturity, and quality of the
finished product. We conducted
a windrow composting study, combining sawdust with either cannery waste,
duck manure, dairy (heifer) manure or potato culls.
Our objectives were to evaluate effects of different feedstock combinations
on key compost process variables, assess compost maturity using a ryegrass
growth bioassay and relate compost process variables to plant growth.
The first 60-100 days of active, thermophilic composting coincided
with the highest microbial respiration across all compost types.
However, the potato cull compost exhibited significantly greater
CO2 respiration and concurrent loss in total C compared to
the other three composts through 150 days of composting.
Carbon to nitrogen ratios declined sharply among all composts
over the first 60 days of composting (from 25-40:1 to 25-12:1).
Dissolved organic carbon declined 2-3 fold after 280 days of
composting among all composts.
The two animal manure composts contained the highest ammonium
N and P concentrations over the first 50 days of composting (~ 500-1800
mg/kg compost C). Compost
NO3-N concentrations remained close to zero for the first
90 days of composting. Over all dates evaluated, cannery
waste compost produced significantly less ryegrass biomass compared
to other three composts (0.59 g/pot vs. 0.69-0.71g/pot). Cannery waste compost appeared to inhibit ryegrass growth in
the first few days of composting (day 16), whereas heifer manure compost
stimulated ryegrass growth at days 43 and 145.
After 250+ days of composting duck manure and potato cull composts
produced significantly more ryegrass biomass than either cannery waste
or heifer manure composts. Duck
manure and potato cull composts had the greatest number of significant
correlations between total ryegrass biomass and compost process variables
including CO2-C respiration, DIW-extractable NO3-N,
C:N ratio, pH, EC and total C.
These findings demonstrate different correlations between plant
growth and indicators of compost maturity, depending on the compost
feedstocks. Furthermore,
they suggest that we don’t have a “universal” set of compost variables
that can be used reliably to assess compost maturity as it relates to
plant growth. Full research paper : Effect of Feedstocks on the Composting Process and Finished Products
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Questions? Comments? Please contact Dr. Leslie Cooperband, UW-Madison |