Vermicomposting is a process in which earthworms are utilized to convert biodegradable organic waste into humus-like vermicast. Past work, mainly on vermicomposting of animal droppings, has shown that vermicompost is an excellent organic fertilizer and is also imbibed with pest-repellent properties. However, there is no clarity whether vermicomposts of organic wastes other than animal droppings are as plant-friendly as the manure-based vermicomposts are believed to be. It is also not clear as to whether the action of a vermicompost as a fertilizer depends on the species of plants being fertilized by it. This raises questions whether vermicomposts are beneficial (or harmful) at all levels of application or if there is a duality in their action which is a function of their rate of application. The present work is an attempt to seek answers to these questions. To that end, all hitherto published reports on the action of vermicomposts of different substrates on different species of plants have been assessed. The study reveals that, in general, vermicomposts of all animal/plant based organic wastes are highly potent fertilizers. They also possess some ability to repel plant pests. The factors that shape these properties have been assessed and the knowledge gaps that need to be bridged have been identified.

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In what is believed to be the first study of its kind, the compositions of the toxic and allelopathic weed parthenium, and its vermicompost, have been investigated using UV-visible and Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, gas chromatography-mass spectroscopy, and scanning electron microscopy. The studies reveal that the weed is transformed into a totally benign organic fertilizer during the course of its vermicomposting. This is indicated by substantial improvements in the humification index, mineralization of organic matter, and degradation of complex aromatics such as lignin and polyphenols into simpler carbohydrates and lipids when parthenium is turned into its vermicompost. There are also significant fragmentation, bio-oxidation and molecular rearrangements of chemical compounds in parthenium vermicompost compared to the parent substrate. In particular, parthenin, which is principally responsible for the toxicity and allelopathy of parthenium, is completely degraded by the vermicomposting of parthenium. The study opens the way to profitable use of the millions of tonnes of parthenium that are generated annually, the continued proliferation of which causes great loss of biodiversity.