CHARACTERISTICS OF COMPOSTS DERIVED FROM WAXED CORRUGATED CARDBOARD

The characteristics of 12 composts containing, by volume, spent mushro om substrate (SMS, 50 percent), waste waxed corrugated cardboard (WCC, 0 percent, 25 percent or 50 percent), and/or pulverized wood wastes ( WW, 50 percent, 25 percent or 0 percent) were measured during two sepa rate windrow composting periods (12-16 weeks). Supplemental N was adde d to some of the composts in the form of poultry manure, and/or soybea n processing wastes. During the first eight to 10 weeks, composts cont aining 50 percent WCC tended to reach and maintain the highest tempera tures, but subsequently cooled most rapidly. Microbial activity (CO2 e volution) also was initially highest in these composts but fell by the twelfth week to levels comparable to composts containing lower levels of WCC. The paraffin wax in WCC containing composts was almost comple tely degraded (>95 percent). After 12 weeks of composting N (1.2-1.6 p ercent DW), P (0.30-0.55 percent), and K (0.9-1.2 percent) concentrati ons were within typical ranges and N and P were highest in composts co ntaining 50 percent WCC. KCl extractable NH4-N (494 mg-N kg(-1)) and N O3+NO2-N (281 mg-N kg(-1)) were highest and lowest, respectively, in c omposts containing 50 percent WCC. Electrical conductivity (4.5-8.5mS/ cm) and pH (7.5-8.5) were high in all composts and highest in composts with 50 percent WCC. Concentrations of phenolic compounds were highes t in composts containing 50 percent WCC, manure, and soybean wastes an d were positively correlated with NH4-N. C:N ratios of all composts we re within an acceptable range (18-23:1).