Rapid composting of groundnut residues through novel microbial consortium: Evaluating maturity, stability, and microbial activity

Abstract

A laboratory pot experiment (Experiment 1) was conducted to determine the optimal ratio of groundnut haulm and shell as composting substrates. The aim was to identify the most effective combination for rapid decomposition under in vivo conditions. The experiment was carried out in 2022, from May to July, using a completely randomized design (CRD) with 6 treatments that were replicated 4 times. The treatment combinations in the pot experiment were as follows: T₁: haulm + shell (1:1), T₂: haulm + shell (2:1), T₃: haulm + shell (3:1), T₄: T₁ + C_n, T₅: T₂ + C_n, and T₆: T₃ + C_n. Here, C_n refers to the cellulose-degrading efficient microbial consortium containing bacterial strains Priestia megaterium DBJ6, Micrococcus yunnanensis DMB9, and fungal strains Aspergillus foetidus DAJ2, Trichoderma atrobrunnium DTJ4, and Phanerochaete chrysosporium CBS129.27. Based on the results (results of chemical and biological properties) of the pot experiment, treatment T₆ was considered the best treatment (the C/N ratio was 14.36 ± 0.444 after three months of decomposition) for further study under in vivo conditions. The in vivo experiment (Experiment 2) was conducted at the Jaguli Instructional Farm of Bidhan Chandra Krishi Viswavidyalaya, West Bengal, India, during the months of August to October in both 2022 and 2023 with two treatments: the normal composting treatment (NC) and the rapid composting treatment (RC). The findings of Experiment 2 showed that organic substrates degraded more quickly (within 90 days) during rapid composting, as evidenced by a decrease in the C/N ratio to below 15 (14.32 and 13.97 on day 90 in 2022 and 2023, respectively). Whereas, normal composting required more than 90 days to achieve a C/N ratio below 20 (23.80 and 23.15 on day 90 in 2022 and 2023, respectively). The RC treatment also showed a higher microbial population and enzyme activity compared to the NC treatment. Therefore, according to the results of this experiment, it can be concluded that the inoculation of the microbial consortium was more beneficial for accelerating the composting process under the same composting circumstances and substrate ratio.