Wormcomposting is a useful alternative to recover the organic carbon and nitrogen and to reduce the pathogenic bacteria in animal manure; but, unlike the composting process, there are no recommendations available about the best initial carbon:nitrogen relationship (CRN) to maximize the nutritional value or to minimize the microbial load of the final wormcompost product. The objective of the study was to evaluate the changes over time on the content of organic carbon (OC), total nitrogen (TN), total aerobic bacteria (TAB), coliforms (Coli) and fungí and yeast (FandY) in composts and wormcomposts prepared with pig manure using different initial CNR. Pig manure, corn stover and water were mixed in different amounts to produce 50 kg heaps that were subjected to a thermophilic process during 28 days under greenhouse conditions. After that, some heaps were inoculated with red worms to produce the wormcomposts. The initial analyzed CNR for composts were: 22, 26, 34 and 46, and for wormcomposts were: 15, 31, 46 and 70. Samples for chemical analysis were taken on days 1, 28 and 140 and samples for microbiological analysis were taken on days 1, 7, 28, 56, 84 and 140 of the study. The data was analyzed using the MIXED procedure with repeated observations over time. In composts, the OC and CNR diminished over time but increased within each time as the initial CNR increased (P < 0.01). The TN rose over time but within each time was lowest at the highest CNR (P < 0.01). The TAB, Coli and FandY counts showed cubic responses over time and showed interactions with the initial CNR (P < 0.01). The TAB, Coli and FandY counts were similar among treatments at 140 days. In wormcomposts, the OC diminished over time but within each time was highest at the highest initial CNR (P < 0.05). The TN rose over time but within each time was lowest at the highest CNR (P < 0.05). At 28 and 140 the CNR dropped compared to the initial CNR and was similar among treatments. The BT, Coli and FandY counts showed cubic patterns over time and showed interactions with the initial CNR (P < 0.05). The TAB, Coli and FandY counts were similar among treatments at 140 days. In summary, the OC and CNR diminished and the TN increased over time in composts and wormcomposts with different initial CNR. Composts and wormcomposts were effective in reducing the microbial load over time regardless of the initial CNR, but the final OC content was greater in the wormcompost. Wormcomposts made from composts with a wide range of initial CNR were highly effective in converting pig manure in a high quality organic fertilizer with a lower load of potential pathogenic bacteria.
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Effect of the carbon:nitrogen relationship on the chemical and microbial composition of composts and wormcomposts made with pig manure
Published: 02 December 2020 by MDPI in The 1st International Electronic Conference on Animals—Global Sustainability and Animals: Science, Ethics and Policy session Climate change and effects on the sustainability of animal systems
Keywords: Compost Wormcompost, Pig manure, Chemical composition, Microbial counts