Detoxification of parthenium (Parthenium hysterophorus) and its metamorphosis into an organic fertilizer and biopesticide

Role of different earthworm species in nullifying the toxicity of Ipomea carnea and enhancing its utility as a phytoremediator

The dreaded weed ipomea (Ipomea carnea), has shown promise as a versatile phytoremediator. But I. carnea plants exude several alkaloids and phenols which are harmful to plants as well as animals. Due to this, the weed imparts as much or more toxicity to the soil as it remediates. These authors have earlier found that upon being vermicomposted by Eisenia fetida ipomea loses its toxicity and becomes a benign organic fertilizer with pest repellant attributes. These findings open up the possibility of using earthworms in those segments of land which are sought to be phytoremediated by ipomea so that the earthworms can keep converting the dead ipomea plants and the debris of live plants to fertilizer. The present work has aimed to determine whether the extent and nature of earthworm impact differs from species to species or is similar across different species. It has revealed that the action of each of the four different earthworm species deployed by the authors caused the C:N ratio of ipomea to change drastically ̶ from 28.20 to 15.95 ± 0.75, bringing the vermicomposts to the category of fertilizers fit for horticulture. The Fourier transform infrared (FTIR) spectra revealed that all the species caused a breakdown of the alkaloids and the phenolic compounds present in ipomea, resulting in the weed's detoxification. The earthworms also effected partial degradation of the lignocellulosic content of ipomea to simpler and more soil-friendly constituents like humic acids. Thermogravimetry, differential scanning calorimetry and scanning electron microscopy corroborated these findings. The influence exerted by the four species of earthworms was similarly beneficial in nature and extent.

An evaluation of selected chemical, biochemical, and biological parameters of soil enriched with vermicompost

The aim of this study was to assess the changes in chemical and microbial properties and enzymatic activity of soil enriched with vermicompost derived from household waste. The vermicompost was tested in the rhizosphere of Larix decidua seedlings cultivated in 10-L pots in: (i) nursery soil (as the control), (ii) soil with 10% v/v vermicompost, and (iii) with 20% v/v vermicompost. The impact of vermicompost was assessed in terms of soil C/N ratio; bacterial, fungal, and nematode counts; and enzymatic activity. It was found that vermicompost increased the C/N ratio from 21 to 32, as well as the content of nitrate from 78 to 134 mg kg^-1, of ammonium from 14 to 139 mg kg^-1, of phosphorus from 92 to 521 mg kg^-1, and of potassium from 142 to 1912 mg kg^-1, compared with the control soil. The abundance of beneficial bacteria was increased (from 8.61 × 10⁷ to 37.9 × 10⁷), along with decreases in microbiological ratios of fungi and bacteria (e.g. fungi/Bacillus from 0.18818 to 0.00425). A significant 2- to 4-fold increase was observed compared with the control in the number of beneficial nematodes belonging to bacterivorous, fungivorous, and predatory groups with no change in the abundance of plant-parasitic nematodes. Addition of vermicompost brought about a change in soil enzyme activity. Vermicompost reduced the activity of alkaline phosphatase only. Both doses of vermicompost led to an increase in the activity of acid phosphatase, inorganic pyrophosphatase, dehydrogenases, β-glucosidase, and urease. Only the higher dose had an effect on increasing the activity of o-diphenol oxidase and proteases. No significant change was observed for nitrate reductase. Also, the presence of antibiotics produced by bacteria was detected depending on the dose of vermicompost, e.g. iturin (ituC) and bacillomycin (bmyB) were found in soil with a dose of 20% v/v vermicompost. Overall, vermicompost produced from household waste can be an excellent organic fertilizer for larch forest nurseries.

Efficacy of the Vermicomposts of Different Organic Wastes as “Clean” Fertilizers: State-of-the-Art

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.