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.

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Utilization of Salvinia molesta, an aquatic weed which is notorious for its allelopathy and invasiveness, has been explored by its vermicomposting. Fourier transform infrared spectroscopy (FT-IR) and plant bioassay tests were conducted to analyze the composition and fertilizer value of S .molesta vermicompost. Germination and seedling growth tests were performed in soil supplemented with vermicompost at levels ranging from 0.75 to 40% by weight of the soil on three common food plants, ladies finger (Abelmoschus esculentus), cucumber (Cucumis sativus), and green gram (Vigna radiata). The influence of S. molesta's vermicompost on some of the physicochemical and biological attributes of the soil was also studied. FT-IR analysis revealed that S. molesta loses its allelopathy, as the chemical compounds that are responsible for it are largely destroyed, in the course of its vermicomposting. There is also an indication that a portion of lignin content of S. molesta is degraded. Vermicompost enhanced the germination success and promoted the morphological growth and biochemical content of the plant species studied. It also bestowed plant friendly physicochemical and biological attributes to the soil. The findings raise the prospect that billions of tons of S. molesta biomass-which not only goes to waste at present but is also a cause of serious harm to the environment-may become utilizable in organic agriculture.

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