Azolla pinnata, Aspergillus terreus and Eisenia fetida for enhancing agronomic value of paddy straw

Dynamics of bacterial community in the foregut and hindgut of earthworms with the nutrition supplied by kitchen waste during vermicomposting

Earthworm gut microbiota is vital in degrading bio-waste during vermicomposting. However, microbial dynamics in earthworm gut during this process are unclear. Thus, the aim is to firstly report the bacterial dynamics in both foregut and hindgut of earthworms over a 28 days' timeframe of vermicomposting by Eisenia foetida with the nutrition supplied by kitchen waste. Results showed that except the changing of the bacterial diversity, composition and structure, dynamics of the foregut and hindgut bacteria also differed during vermicomposting which related to the changes of nutrient provision. Day 3 was a turning point. The abundant bacteria of the top 20 % genera nearly did not overlap between the foregut and hindgut. In the end of vermicomposting, a remarkable stable bacterial structure appeared in the hindgut compared to somewhat muddled one in the foregut. Understanding the dynamics of earthworm gut microbiota enables the improvements to regulate the efficiency of organic waste vermicomposting.

An overview of underutilized benefits derived from Azolla as a promising biofertilizer in lowland rice production

Currently, there is no doubt that Azolla can compensate for the nitrogen requirements of rice in different agroecological zones. Compared to synthetic N-fertilizers, Azolla has various positive impacts on lowland rice production, including improving soil fertility, minimizing weeds, increasing soil organic carbon, improving microbial biomass, and thus nutrient cycling and enhancing rice growth and yield. However, Azolla has not been accepted globally by rice farmers for field use and so far, farmers are relying on increasing rates of synthetic N fertilizers instead of taking advantage of Azolla which will improve long-term soil fertility and health. This systematic literature review and scientific evidence could help policymakers, scientists and researchers to understand the benefits, limitations, and innovative ways of utilizing Azolla as a cost-effective and eco-friendly amendment in rice production. The paper uses Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) method to review the hidden potential of Azolla as a biofertilizer in paddy and summarizes its benefits and problems by collecting information from different sources and presenting under different subheadings such as critical factors affecting Azolla growth and nitrogen fixation, nitrogen fixation of Anabaena Azollae and their contribution in soil health, release and availability of Azolla-N to rice, amounts and time of Azolla inoculation, influence of Azolla on ammonia volatilization, contribution of Azolla to yield and yield components of rice, and impact of Azolla on weed emergence in rice cropping system. Literature indicated that the use of Azolla as green manure incorporated before rice transplanting or grown together with rice and left until a few days of harvest alone or in combinations with other synthetic fertilizers in the lowland rice production saved the nitrogen requirement of rice up to 60 kg N ha^-1, it enhances the availability of nutrients, improves physiochemical properties of soils, minimizes soil salinity, reduces the soil pH, and minimize weed germination. However, it was observed that incorporating Azolla as green manure is labor-intensive, and maintaining the Azolla inocula and phosphorous requirement are major restrictions for farmers. Therefore, understanding mechanism of spore production, educating farmers on cheaper alternative ways of Azolla application, and testing different species of Azolla over different agroecological zones will help in maintaining Azolla biomass and applying it at low cost for further environmental conservation.

Vermicomposting: A Valorization Alternative for Corn Cob Waste

As vermicomposting has become a viable alternative for the valorization of organic waste; the objectives of this research were to (1) assess the feasibility of said process for corn cob waste (corn cobs and corn husks) and (2) evaluate the operation conditions for the biodegradation of different mixtures with load material (LM). LM did not include animal excreta as a nitrogen source, a practice widely used in a range of studies. The experiment consisted of an initial phase of pre-composting in order to obtain a partially stabilized substrate. Subsequently, four separate mixtures were made consisting of corn cob waste mixed with consistent load material (LM) containing vegetable waste and eggshells (CR, M1, M2, M3) to obtain a balance substrate able to facilitate degradation using Eisenia fetida earthworms. The following parameters were analyzed during the control process: temperature, pH, humidity, organic material (OM), total organic carbon (TOC), total nitrogen (TN) and carbon/nitrogen (C/N) ratio. The analysis of the final values of the stabilized mixtures showed that vermicomposting is indeed a feasible alternative for the degradation of corn cob waste for use as a soil improver.

Unveiling the Efficiency of Psychrophillic Aporrectodea caliginosa in Deciphering the Nutrients from Dalweed and Cow Manure with Bio-Optimization of Coprolites

There is an immense demand for vermicomposting employing psychrophilic vermiculture (Aporrectodea caliginosa) for management of wastes under the Himalayan ecosystem. Dalweed (weeds from the world-famous urban Dal Lake) and cow manure (CM) are cheaply and abundantly available bio resources in Kashmir valley. Dalweed (DW), disposed of in the heart of the city, ascribes unpleasant effects on tourism and the natural ecosystem. Initial substrate mixtures of DW and CM with different ratios (CM100, DW100, CM80:DW20, CM60:DW40, CM40:DW60 and CM20:DW80) and castings harvested were analyzed for the following parameters: pH, TOC, TN, NO3- P, K, Fe, Zn, C:N, C:P, and C:S ratio. The results of a 56day study revealed in consistency and disparity towards the bio-optimization of coprolites depending upon the type of waste residue and mixture ratio used. Treatments with medium to low dalweed residues (CM60:DW40 followed by CM80:DW20) were found to be optimum and significantly primed chemical properties of castings using A. caligenosa. C:N, C:P, and C:S ratios showed a non-linear response with maximum decrease in C:N ratio by 35%, C:P ratio by 38% in CM100, and C:S ratio by 67% in DW100. Humification ratio, humification index, and percent humic acids were changed across all the treatments with the highest respective values of 21.33 ± 1.05, 11.33 ± 0.76, and 47.83 ± 0.76 for CM60:DW40. Results also showed that the earthworm population and biomass significantly increased with the highest respective increments of 57.53% and 74.88% in CM60:DW40 over initial values. Moreover, the highest number of cocoons (95.67 ± 1.17) were recorded within CM60:DW40 and the lowest in the control (43.33 ± 1.53). Dehydrogenase and fluorescein diacetate activities were inconsistent with the highest in CM40:DW60 (64.64%) and CM20:DW80 (63.54%) respectively over the initial substrates, while highest urease activity (74.40%) was observed from CM100. The results highlight the role of A. caliginosa in sustainable transformation of CM and DW with insightful, beneficial, and priming impacts on castings for its agronomic value.

An insight to municipal solid waste management of Varanasi city, India, and appraisal of vermicomposting as its efficient management approach

Varanasi, India's historic cultural capital, struggles with efficient waste management practices. This impacts environment and human well-being in terms of waste generation that is estimated around 550-650 TPD with a generation rate of 0.42 kg capita^-1 day^-1 (n = 117). The present study aims to explore and characterize wastes, current practices, ecological profiling, and phytotoxicity of an abandoned open dumping site, and vermicomposting of organic fraction of municipal solid waste (OFMSW) as sustainable waste management approach. Compositional analysis of waste indicates organic fraction (46.13%) as a major component along with a considerable amount of heavy metals. The calorific value and moisture content of municipal solid waste (MSW) was 2351.4 cal g^-1 and 34.72%, respectively. Ecological profiling of the dumping site revealed that floral diversity and ecological species/indicators were negatively affected. Likewise, phytotoxicity results displayed a negative impact on germination and physiology of maize (Zea mays L.) plants grown on dumping site soil. Vermistabilization of OFMSW showed a significant increase in N (56.10-89.48%), P (33.93-82.87%), and K (25.55-50.42%) and a decrease in total organic carbon (15.15-24.81%). Similarly, C/N and C/P ratios decreased by 1.89-2.51 and 1.72-2.18 folds, respectively. A survey of stakeholders suggested that open dumping was the main practice adopted by Varanasi Municipal Corporation (VMC) during 2013-2015. Recently (2017-2018), VMC adopted different methods, such as door-to-door collection and source segregation for effective waste management. Waste characteristics and nutrient profile of the vermicompost explains that vermicomposting could be used for efficient waste management in Varanasi, further reducing the collection, transportation, and disposal costs of waste, which enables to close the loop and move towards a circular economy. Moreover, implications of existing waste management practices and possible management options need to be addressed scientifically. Therefore, this research outcome will help in designing a successful waste management plan for Varanasi and other cities with similar waste characteristics.

Analysis and advanced characterization of municipal solid waste vermicompost maturity for a green environment

Rapid demographic expansion along with increasing urbanization has aggravated the problem of solid waste management. Therefore, scientists are seeking waste management methods that are eco-friendly, cost effective and produce immediate results. In the developing world, municipal solid waste (MSW) contains mostly organic substances, therefore vermicomposting could be a better and cost-effective option for waste management. In this study, vermicomposting of organic portion of MSW with cow dung (additive) was performed using Eisenia fetida. The results showed significant (p < 0.001) decline in pH (13.17%), TOC (21.70%), C: N (62.53%) and C: P (57.66%) ratios, whilst total N (108.9%), P (84.89%) and K (21.85%) content increased (p < 0.001) in matured vermicompost. Different enzymatic activities declined during termination phase of vermicomposting experiment with maximum decrease of 41.72 (p = 0.002) and 39.56% (p = 0.001) in protease and β-glucosidase, respectively. FT-IR, TGA, DSC and SEM studies suggested that final vermicompost was more stabilized as compared to initial waste mixture, characterized by reduced levels of aliphatic materials, carbohydrates and increase in aromatic groups possibly due to biosynthesis of humic substances. Both, the conventional (physicochemical and enzyme activity) and advanced techniques depict maturity and stability of the ready vermicompost. However, FT-IR, TGA, DSC and SEM were proved to be more promising, fast and reliable techniques over conventional analyses.

Azolla pinnata, Aspergillus terreus, and Eisenia fetida for fasterrecycling of nutrients from wheat straw

A vast amount of surplus wheat straw/stubble (a carbon-rich bioresource) is wasted every year by burning. Harmful gases and residue matter released due to burning cause harmful effects on the environment and human health. Therefore, there is a strong need to recycle this bioresource in a sustainable manner. In the present study, wheat straw (W) was spiked with cattle dung (C), Azolla pinnata (A), and Aspergillus terreus (F) to make eight different treatments (1 kg each), viz. W (1 kg), WC (666 g + 334 g), WA (980 g + 20 g), WF (980 g + 20 ml), WCF (666 g + 314 g + 20 ml), WCA (666 g + 314 g + 20 g), WFA (960 g+ 20 ml + 20 g), and WCFA(666 g + 294 g + 20 ml + 20 g), and subjected to vermicomposting (Vcom) and aerobic composting (Acom). A comparison was made for the time required for degradation and nutrient profile of the products. The fastest recycling of wheat straw/stubble (120 days) was observed in WCA and WCFA, but the nutrient quality of WCA was better (N 18.67, P 3.88, K 38.84 g/kg). In the Acom group, longer time was required for degradation of various mixtures, but in this group also, WCA was degraded first of all (138 days) and yielded a product with the best nutrient quality (N 14.77, P 2.56, K 28.80 g/kg). Maximum growth of E. fetida and maximum number of hatchlings were observed in WCA while the highest cocoon production was observed in WCFA. It was observed that azolla enhanced conversion of wheat straw into a nutrient-rich product for agronomic use. Thus its use will reduce the amount of cattle dung in the mixture and the bulk to be handled by the farmers for ecosafe disposal of surplus straw/stubble. Therefore, this technology can be adopted as an alternative to burning.

Effects of different lipid contents on growth of earthworms and the products during vermicomposting

In China, the production of kitchen waste was more than 97 million tons per year in 2016. The high lipid content of kitchen waste makes it hard to degrade. Vermicomposting is a kind of low-cost biotechnology through the combination of earthworms and microbes, which could be considered in converting kitchen waste to valuable products. However, the effect of the lipid in kitchen waste on earthworms and composting is not known yet. The objective of this study was to analyze the effects of lipid on vermicomposting and to derive the most suitable lipid content in vermicomposting. In our study, kitchen waste with four different lipid contents was prepared: 0% (A), 5% (B), 10% (C) and 15% (D). The earthworm growth and chemical characters of substrates were measured at the interim (14 days) and the end (28 days) of vermicomposting. Our results showed that the high content of lipid had negative effects on growth of earthworms and products in vermicomposting. The kitchen waste with lower lipid content could be better composted by earthworms. The average body weight of the earthworm increased by 9% in treatment A. Total nitrogen, available phosphorus, available potassium and nitrate nitrogen of treatment A with 0% (measured value: 5%) lipid content were significantly higher than those in other treatments. Meanwhile, treatment A had the lowest carbon/nitrogen ratio which might be due to hindrances in the breathing and activities of earthworms. The high content of lipid makes growth of aerobic bacteria such as nitrifying bacteria difficult.