Changes of carbon, nitrogen, phosphorous, and potassium content during storage of vermicomposts prepared from different substrates

Ammonia Volatilization and Greenhouse Gases Emissions during Vermicomposting with Animal Manures and Biochar to Enhance Sustainability

There is a huge potential for nutrient recovery from organic waste materials for soil fertility restoration as well as negative environmental emission mitigation. Previous research has found vermicomposting the optimal choice for converting organic waste into beneficial organic fertilizer while reducing reactive N loss. However, a great deal of the processes of greenhouse gases (GHG) and ammonia volatilization during vermicomposting are not well-documented. A field vermicomposting experiment was conducted by deploying earthworms (Eisenia fetida) with three types of agricultural by-products-namely, cow manure (VCM), pig manure (VPM), and biochar (VBC)-and crop (maize) residues compared with traditional composting (COM) without earthworms in the Sichuan Basin, China. Results showed that vermicomposting caused a decrease in electrical conductivity (EC) and total organic carbon (TOC) while increasing total nitrogen (TN). The greatest TN increase was found with VCM. The cumulative NH₃ volatilization in COM, VCM, VPM, and VBC during experimental duration was 9.00, 8.02, 15.16, and 8.91 kg N ha^-1, respectively. The cumulative CO₂ emissions in COM, VCM, VPM, and VBC were 2369, 2814, 3435, and 2984 (g·C·m^-2), while for CH₄, they were 0.36, 0.28, 4.07, and 0.19 (g·C·m^-2) and, for N₂O, they were 0.12, 0.06, 0.76, and 0.04 (g·N m^-2), respectively. Lower emissions of N₂O, CH₄, and NH₃ were observed in VBC. We concluded that earthworms, as ecological engineers, enhanced reactive nutrients and reduced ammonia volatilization during vermicomposting in our test system. Overall, vermicomposting is proposed as an eco-friendly, sustainable technique that helps to reduce environmental impacts and associated health risks.

Evaluating changes in microbial population and earthworms weight during vermicomposting of cow manure containing co-trimoxazole

BACKGROUND

Transmission of pathogens such as fecal coliforms is regarded as a significant concern about using livestock manure in agricultural applications.

PURPOSE

The aim of this study was to evaluate the effects of vermicomposting on fecal coliforms in cow manure containing co-trimoxazole as a widely used drug for cow diseases in animal husbandry.

METHODS

Adaptation process of earthworms was carried out in two phases for 6 weeks; then, the main process was fulfilled in 9 weeks. The final weight of cow manure per reactor was 3.5 kg. 120 g of earthworms added to each reactor (approximately 280-300 numbers in the reactor). Co-trimoxazole was also prepared with a purity of 99% from Pakdarou Co., Iran, and added to the reactors at concentrations of 10, 20, 50, and100mg/kg. Organic carbon, total Kjeldahl nitrogen (TKN), carbon-to-nitrogen (C:N) ratio, as well as phosphorus content of the reactors were measured. Fecal coliforms and parasite eggs were counted using standard laboratory methods (i.e. the Iranian Compost Standard) for 8 weeks.

RESULTS

The results revealed a decrease in organic carbon, C:N ratio, and co-trimoxazole content but a rising trend in TKN and phosphorus levels. The weight of earthworms also increased at the end of the process in all reactors, except for one case. A significant reduction was observed in fecal coliforms and parasite eggs at the end of the vermicomposting.

CONCLUSIONS

According to the results, earthworms could be active in cow manure vermicomposting including 10-100 mg/kg concentration of co-trimoxazole antibiotic. The vermicomposting seems to be an effective method for reducing fecal coliforms and parasites in cow manure. As well, co-trimoxazole in common concentration could not have any effects on the ability of earthworms. At the end of the vermicomposting, all parameters were placed within the ICS (National) - Grade 1.

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.

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

In the present study rice straw (R, control) was mixed with Cowdung (C), Azolla (A) and cellulolytic fungus Aspergillus terreus (F) in different combinations viz. RC, RA, RF, RCF, RCA, RFA and RCFA and subjected to aerobic composting (Acom) and vermicomposting (Vcom - with Eisenia fetida). It was found that addition of azolla and cattledung to two parts straw(RCA-666: 314:20 g) caused fastest degradation (105 days), gave maximum population buildup of E. fetida (cocoons, hatchlings and worm biomass), highest decline in pH, EC, TOC and C/N ratio and maximum increase over control in N(17.72%), P(44.64%), K(43.17%), H (7.93%), S (14.85%), Ca(10.16%), Na(145.97%), Fe(68.56%), Zn(12.10%) and Cu(32.24%). Rice straw (R) took longest time for degradation i.e. 120 and 140 days and had lowest content of nutrients in Vcom as well as Acom group. RCFA was also converted into Vcom at the same time but other parameters were less than RCA except for highest content of B (19.87%), Mg(21.27%) and Mn (5.58%). Bioconversion of three parts straw (RCA-735:245:20 g) was also faster (110 days) with vermicomposting than all the mixtures of Acom group (130–140 days) but nutrient content was slightly less than RCA with 2 parts straw. The results show that azolla reduces dependence on cattledung for recycling the carbon rich rice straw and enhances its agronomic value.