Identification of microbial populations in blends of worm castings or sugarcane filter mud compost with biochar

Authors: Wright, Maureen; Lima, Isabel

Submitted to: Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/20/2021
Publication Date: 8/22/2021
Citation: Wright, M.S., Lima, I.M. 2021. Identification of microbial populations in blends of worm castings or sugarcane filter mud compost with biochar. Agronomy. 11(8):1671. https://doi.org/10.3390/agronomy11081671.
DOI: https://doi.org/10.3390/agronomy11081671

Interpretive Summary: Worm castings are the product of vermicomposting, the conversion of organic material by earthworms to a byproduct that can beneficially enhance soil. Sugarcane filter mud can be converted by composting to a beneficial soil amendment. The consistency of worm castings and filter mud is not conducive to even dispersal in or on soil. Previous work has shown that blending with biochar can provide a consistency suitable for mixing with soil, without affecting the beneficial physico-chemical or microbial properties of worm castings or mud compost. While microbes were enumerated in the previous study, this work reports the qualitative identification of the microbes present in the blends. The identified microbial populations were found to include several that contribute to plant growth, and to not include any that are known to cause human illness. The data support future studies of the potential for these blends to replace non-sustainable soil amendments such as peat moss.

Technical Abstract: Soil amendments are used to improve soil quality, thereby enhancing plant growth and health. Efforts have been made to replace synthetic chemical enhancers. It is also preferable to not use natural products such as peat moss, the harvesting of which can be harmful to marine ecosystems. Viable replacements include worm castings, which can contribute beneficial microbes as well as physico-chemical amendments. Another potential soil amendment is the compost produced from sugarcane processing byproducts. While the texture of these two materials is not ideal for even dispersal onto fields, the addition of biochar improves the texture. Previous work demonstrated that blending them with biochar from sugarcane byproducts added physico-chemical benefits, while not quantitatively reducing the microbial load, even after storage. Microbial populations of the blends in the present study were found to (1) contain taxonomic groups that contribute to plant health and (2) not contain human pathogens. Based on the quantitative and qualitative microbial analyses, it has been determined that 50% or less biochar in a blend will allow maintenance of beneficial microbes in stored samples.