Physicochemical and microbial profile of oil palm empty fruit bunches compost treated with effective microorgnisms

Abstract

This study investigated the effects of Effective Microorganisms (EM·1™) on the composting process of ground oil palm empty fruit bunches (EFB). The maturity of the compost was monitored based on its important physical (temperature, pH and colour), chemical (organic and inorganic components) and microbiological properties. The compost with the addition of EM·1™ (ETC) matured 8-10 days earlier than the control sample (Ctl). The prolonged thermophilic phase was not observed for ETC because ETC could reach 50-55 oC within 2 to 3 hours on the first day of a 10-day experiment and maintained the temperature between 26-42 oC until the end of the process. Compared to control, ETC decreased the total organic carbon (TOC) and carbon to nitrogen (C/N) ratio by 10.78% and 17.26, respectively, but increased the microbial population (37.4% higher than Ctl) and the production of essential inorganic elements (Mg, K, Ca, Cu and B), as well as the key metabolite (5- aminolevulinic acid) for plant growth. The increment of nitrate nitrogen (NO3 --N) was found to be higher in ETC, this may be due to a decrease of ammonium nitrogen (NH4 +-N) in the process of nitrogen mineralization. Both Ctl and ETC reached a NH4 +/NO3 - ratio of 0.16 after maturation of the compost. Interestingly, the pH of the compost was found acidic (between pH 4.5 and 5.0) for the first week of composting, and then gradually increased to neutral and slightly alkaline pH (around pH 7.5-8.5) at the end of the process. The acidic condition was due to the accumulation of organic acids. The findings of this study concluded that the inoculation of EFB compost with EM·1™ could provide a better degradation of EFB compared to Ctl.