Rapid biomax thermophilic composting effects on quality, nutrient release and fertiliser value of chicken litter composts.
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Large accumulation of organic waste produced from intensive animal production systems pose challenges for disposal and direct land application of these materials adversely affect the environment. Composting aids to reduce waste volume and produce a stable product, rich in nutrients, that is valuable for soil fertility improvement. The Biomax system has been developed as a system to rapidly compost organic wastes at 70-80 oC in a 24 h period. The stability, quality and fertiliser value of the compost needs to be understood. Considering the high temperatures involved it would be essential to establish whether or not the addition of the enzyme is entirely necessary in the process. The objectives of this study was to determine effects of the Biomax composting time and enzyme addition on chicken litter compost stability, quality, nutrient release, in soils, and dry matter yield and nutrient uptake of spinach. Biomax composts were produced from mixtures of chicken litter and other organic wastes with (W) and without (N) the BM1 enzyme. Compost samples were collected after 1, 6, 12, 18 and 24 h of composting, and analysed for pH, EC, total C, N, and P, exchangeable bases, trace elements, fulvic and humic acids and Escherichia coli and Salmonella spp. An incubation study was carried out with final composts (after 24 h of composting) applied to soil at 0, 1, 2 and 3 % (w/w) and destructive sampling was done after 0, 7, 14, 28, 42 and 56 days of incubation. The samples were analysed for pH, mineral N, available P, and bases. A glasshouse experiment was also conducted using the final compost produced with the BM1 enzyme. The compost was applied as the nitrogen source to 3 kg soil at 0, 2.5, 5, 10 and 20 t/ha and spinach (Spinacia oleracea) grown for eight weeks. The pH of compost with the BM1 enzyme decreased with composting time while the one without the enzyme increased between 1 and 12 h. Total C, electrical conductivity (EC), carbon to nitrogen ratio (C:N) and humification ratio (HR) were not affected by composting time for both composts. Total N increased up to 18 h of composting and became constant afterwards for both composts. Pathogenic organisms E. coli and Salmonella species were not detectable in all composts irrespective of composting time. In the incubation study NH4-N levels initially were similar statistically for all rates of both composts, except for soil treated with 1% of compost with the enzyme, which had lower NH4-N than that amended with 3% of the compost without the enzyme. Levels of soil NO3-N showed rapid increase in all treatments including control between 14 and 28 days of incubation and remained constant thereafter. The amount of available P was higher in soil treated with 3 % of both composts. There was no differences in spinach tissue nitrogen concentrations among the different application rates of Biomax compost. Spinach dry matter yield and N uptake improved with addition of compost. The findings of this study implied that the Biomax system is not effective in stabilising chicken litter into compost but it effectively sterilizes the organic waste materials and that the resultant composts rapidly release nutrients at sufficient rates to improve dry matter yield and nutrient uptake of spinach. Keywords: Biomax compost, mineralisation , nutrient composition, plant nutrient uptake, spinach (Spinacia oleracea).