RESUMEN
As reported recently by the present authors, vermicomposting by the epigeic earthworm Eisenia fetida transforms the highly ligninous and allelopathic aquatic weed salvinia (Salvinia molesta) into a benign organic fertilizer. The present study was carried out with four other earthworm species, including three epigeic species of different sizes and phytophagic habits: Eisenia andrei, Lumbricus rubillus, and Perionyx sansibaricus. One anecic species, with geophytophagous habits, was also explored for comparison: Drawida willsi. The objective was to see whether the type of salvinia transformation caused by E. fetida is a general phenomenon or whether there are significant differences in the nature of biocomposts generated by different earthworm species. Accordingly, the characteristics of the biocomposts separately generated by each of the six species mentioned above were assessed with UV-visible spectrophotometry, Fourier-transform infrared spectrometry, differential scanning calorimetry, thermogravimetry, and scanning electron microscopy. The studies reveal that, with minor variations, the biocomposting by all four species was able to remove the intransigence of salvinia and impart plant/soil-friendly attributes to it in substantial measures. All the findings obtained with different techniques corroborated each other in arriving at this conclusion. Hence, it can be said that, in general, biocomposting by earthworms takes away the toxicity of pernicious weeds such as salvinia, converting them into plant-friendly and soil-friendly biofertilizers.
RESUMEN
With vermireactors designed on the basis of the concept of high-rate vermicomposting recently introduced by S.A. Abbasi and co-workers, it has become possible to directly vermicompost phytomass, including pernicious weeds. It has also been shown that upon vermicomposting, even toxic and allelopathic weeds get transformed into highly plant-friendly and soil-friendly organic fertilizers. Pre-existing vemireactors were not able to achieve direct vermicomposting of weeds or other plant biomass, for reasons explained in the main text. But it is necessary to ascertain whether vermireactors can be operated indefinitely with problematic weeds and whether earthworms born in such vermireactors have adequate health and reproductive ability to sustain the vermireactors interminably. Hence the present work has been undertaken to assess the performance of three successive generations of four earthworm species in terms of their ability to vermicompost the highly ligninous aquatic weed salvinia and reproduce in the vermireactors solely fed by it. It was seen that in all cases the first generation of animals, which had been born and grown to adulthood in cow-dung fed vermiculture systems, took time to adapt to the weed-feed, but did so and remained healthy. The next generation which was born and raised in salvinia-fed vermireactor was significantly more efficient in vermicomposting salvinia while the third generation was still more efficient in comparison to the second generation. The trend of third generation being superior to the second and the second being superior to the first was manifest in the production of offspring (juveniles and cocoons) as well. All-in-all the findings, covering 16 months of uninterrupted vermireactor operation, reveal that earthworms tend to get acclimated to have salvinia as their exclusive feed and the successive generations of earthworms that are born and grown in the weed-feed reactors manifest not only greater vermicomposting efficiency but also superior reproductive ability than the earthworms which had been raised on animal manure.
Asunto(s)
Oligoquetos , Tracheophyta , Animales , Bovinos , Femenino , Fertilidad , Reproducción , Estiércol , Suelo , MalezasRESUMEN
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.
First-ever study which establishes the general applicability of earthworms in nullifying the toxic impacts caused by ipomea during its use in phytoremediation, thereby greatly enhancing ipomea's value as a phytoremediator. The studies also provide an avenue for the utilization of the otherwise worthless ipomea harvested after phytoremediation or from natural stands.