Qualitative evaluation and economic assessment of Dal-lake aquatic weed vermicompost prepared in conventional vermi-bed and smart vermicomposting bin

The study emphasized in understanding the dynamics of vermicomposting in conventional vermi-bin and smart vermicomposting bin using Dal Lake aquatic weed as substrate with turning frequency of 10 days and 20 days and 20, 40 and 60 days degradation period. In vermi-bed method, the materials were turned manually and a spiral mixer was used in smart vermicomposting bin. The results showed that pH, organic carbon and C: N ratio dwindled by 3.28%, 16.36% and 5.57% and there was an increase in EC by 22.39%, N 14.03%, P 37.78% and K 5.85% with 10 days turning frequency in vermi-bed vermicomposting system. In 20 days turning frequency, the values were 3.02%, 22.58%, 13.96%, 42.86%, 6.92%, 11.81%, respectively. When the dal lake aquatic weed was degraded in smart vermicomposting bin, it was observed that pH, organic carbon and C:N ratio shrunk by 5.63%, 14.94% and 24.88% with an increase in 11.23% N, 26% P, 10.4% K in 10 days turning frequency and 60 days degradation period. In 20 days turning interval, the values recorded were 6.23%, 14.29%, 24.56%, 10.99%, 20%, 16.77%, respectively. The cost of preparation of 1 kg of vermicompost was Rs. 20 and Rs. 13 in vermi-bed and smart vermicomposting bin. The bene�t cost ratio of smart vermicomposting bin was higher (1.78) than vermi-bed process in the second year. The study can help to shift from conventional to smart vermicomposting system to automate the system, reduce the dependence on manual labour and achieve the dream of organic agriculture.


Introduction
The transformation and recycling of the agricultural waste is perceived as the rst step towards the sustainability of ecosystem, protection of the environment and safeguarding the interests of human health [1].The human intervention and natural phenomenon have resulted in sporadic growth of weed in the Dal-Lake, inducing obstructions in the aquatic ecosystem, choking of water channels and threatening human health [2].The aquatic weeds usually possess morphological adaptation features to adjust and adopt in diverse climatic conditions [3].Dal lake is world famous for its beauty and landscape.However, the lake often witnesses the problem of weed infestation [4], choking its drainage channels, severely impacting the vegetable production system and threatening the human health [5].A number of chemical and biological methods were tested [6], but most of them were ineffective owing to its large volume, thick stem and costly [7].The dal lake aquatic weed is rich in nutrients and can be converted into nutrient rich vermicompost for improving the fertility of the soil [2].
Vermicomposting is a cost-effective, viable and sustainable approach [2,8]] for conservation of diversity and integrity of the agricultural ecosystem [9,10].The process of vermicomposting relies on the metabolic growth of Earthworm to transform the organic waste into nutrient rich vermicompost [11].The chemistry of the vermicomposting process of biodegradable materials involves the breakdown of complex molecules into monomers.The technique of vermicomposting can be e ciently utilized on weed species to prepare a high-quality end product [12].The earthworm is termed as 'ecosystem engineers' [13].Two species of earthworm-Eisenia fetida and Eudrilus euginae with high conversion e ciency and wide substrate base is often used for vermicomposting process [12].The cowdung is mixed with the substrate owing to its palatability and appropriate C: N ratio [8].Vermicomposting is preferred for the substrates with high lignin and cellulose content [14].Vermicomposting relies on earthworms to ingest the organic substrates for particle size reduction and degradation.The type of the substrate de nes the degradation pattern as harder materials are rigid to be ingested easily by the earthworms.
The vermicompost supplies nitrogen, phosphorus, potassium and micronutrients [15] and improves physical, chemical and biological properties of soil [16].The improvement in the fertility of soil through the application of vermicompost can promote plant growth, and reduce the dependence on hazardous chemical fertilizers.[17] highlighted the importance of earthworms in bolstering the quantity of bacteria, fungi, swelling the performance of cellulose, urease and alkaline phosphatase, thereby, improving the quality of the vermicompost.
The rate of degradation of the agricultural biomass relies heavily on the type of substrate, number of turnings and degradation period [18].The turning of the degrading substances is essential to distribute the moisture uniformly, increase the contact surface of the earthworms and maintain temperature parity [19,20].Conventionally, the vermicomposting is carried out in pits/bins with heavy reliance on manual labour.The material is shredded and allowed to degrade in presence of earthworms to prepare a ne peat like material [21].However, a smart vermicomposting bin was developed and evaluated to degrade the organic matter with less manual intervention [2].It comprised of feeding hopper, shredding section, spiral mixing chamber, degradation bin and harvesting gate.The boundaries were covered double layered polycarbonate sheet to protect the earthworms from predators.[22] concluded that the conservation, protection from predators and maintaining the feasible ecosystem for the growth of earthworms is imperative for the sustainability of the vermicomposting process.
In the current study, the focus was laid towards the performance evaluation and economic assessment of the conventional vermi-bin with smart vermicomposting bin using Dal-lake aquatic weed as substrate.
The idea was to lend a support towards mechanical intervention and automation in vermicomposting process.The conventional process of vermi-bed method has turned unsustainable owing to increasing wage rates, shrinking land resources and associated drudgery.There is less literature available with respect to mechanical intervention and automation and demands systematic and scienti c approach to adopt the latest techniques for turning this profession pro table and economical.

Materials And Methods
2.1 Availability of Dal lake aquatic weed: The dal lake aquatic weed was collected from the outer periphery of the Dal lake.The investigation was carried out in the year 2018-2019 at Divisional eld of Vegetable Science and workshop of College of Agricultural Engineering and technology (COAE&T), Sher-e-Kashmir University of Agricultural Sciences and Technology of Kashmir, (SKUAST -K), Shalimar, Srinagar.For vermi-bed process, the material was subjected to manual size reduction and allowed to undergo pre-digestion phase for one week, Fig. 1.However, in case of smart vermicomposting bin, there was a separate chopper for particle size reduction.

Experimental methodology:
Vermi-bed: Vermi-bin is a 12x4x2 feet rectangular bin in which the chopped pre-digested dal lake aquatic weed mixed with two-week-old cow dung in the ratio of 1:1.Two kilogram of earthworm (Eisenia fetida) procured from Division of Vegetable Sciences, Faculty of Horticulture, SKUAST -K was added to act as bio-agent in the vermicomposting process.The climate of experimental site was temperate type with moderately hot summers and cold winters, Fig. 2. The moisture level was maintained at 60% throughout the process by adding water after each turning.The samples were collected at regular intervals to assess the degradation pattern of Dal Lake aquatic weed.
Smart vermicomposting bin: The smart vermicomposting bin comprised of feeding hopper, shredding rollers, rectangular degradation chamber, spiral mixer and harvesting gate, Fig. 3.The dal lake aquatic weed was passed through the shredding section to reduce the particle size.The pre-digested cow dung was added along with two kilogram of earthworm Eisenia fetida.The materials were mixed with the help of spiral mixer to distribute the moisture and earthworms uniformly.Two set of experiments were laid with 10 days and 20 days turning frequency interval.The moisture content was added at every turning with the help of an Arduino controlled system to maintain moisture level at 60 per cent.

Plan of experiment:
The dal lake aquatic weed was degraded in conventional vermi-bed and smart vermicomposting bin (14) with turning interval of 10 days and 20 days and degradation period of 20 days, 40 days and 60 days, Table 1.The responses were measured in terms of pH, electrical conductivity, available nitrogen, available phosphorus, available potassium, organic carbon and C: N ratio.The treatment combinations involving independent parameters were organized to provide a clear picture of the degradation pattern responsible to produce vermicompost, Table 2.
Table 1: Plan of experiment to assess the degradation potential in conventional vermi-bed and smart vermicomposting bin

Parameters
Vermicomposting process Levels Responses Turning frequency Conventional vermi-bed 10 days (T 10 ) • pH • EC (dS m -1 ) • Available Nitrogen (g kg -1 ) • Available Phosphorus (g kg - 1 ) • Available Potassium (g kg -1 ) • Organic carbon (%) • C:N ratio  Measurement of performance Indices: The material in the tetra vermi-beds and smart vermicomposting bin was turned at regular intervals of 10 days and 20 days frequency and samples were collected.The samples were subjected to drying, grinding process and passed through 2 mm mesh size screen to prepare the samples for chemical analysis [23].The readings were measured in triplicate.a) pH: It serves as an indicator to highlight the presence of hydrogen ion concentration.It was measured by taking 10 g sample in a 100 ml beaker and adding 25 ml of distilled water.The contents of the solution were stirred for 30 minutes.The pH value was measured by means of a digital pH meter [24].b) Electrical conductivity: The electrical conductivity highlights the presence of soluble salts in the form of electrical charge.Electrical conductivity serves as an index to test the phytotoxicity of the vermicompost [25].It was measured using 10 g sample and mixed with 25 ml of distilled water.The sample was kept overnight without disturbing.The electrical conductivity was then measured with the help of an EC meter, Table 3. c) Available nitrogen: The nitrogen content is perceived as an essential criterion to decide the fertility status of the vermicompost.The available nitrogen was determined using Kjeldahl method [26].About 0.5 g of the vermicompost was distilled with 0.32 % potassium permanganate and 2.5 % sodium hydroxide solution.The contents were stirred and ammonic gas was allowed to escape.The ammonia gas was absorbed in 4 % boric acid solution.The boric acid mixture was titrated with 0.02 N sulphuric acid till the original pink color of boric acid solution was obtained.The chemical reactions responsible for the measurement of nitrogen were  C:N ratio --- [23] e) Available phosphorus: The phosphorus content also depicts the fertility status of the vermicompost.About 20 ml of 0.5 M sodium bicarbonate solution was added to 1 g of sample.The solution was stirred thoroughly and ltered.Ammonium molybdate solution and stannous chloride was added to the ltered solution.The intensity of the blue color obtained was measured at 660 nm using a spectrophotometer.
f) Available potassium: Potassium is essential to maintain the transpiration rate in plants, intake and exhale of carbon dioxide and activation of enzymes.It was measured by ame photometer.The available potassium was extracted from the sample by shaking it with 1N neutral ammonium acetate solution and contents of the solution were ltered.The ltered samples were placed one after the other to measure the potassium concentration through ame photometer [23].
g) Organic carbon: The release of the gases results in the reduction in the carbon content of the organic waste.About 0.5 g of the vermi-compost sample was treated with 10 ml of 1N potassium dichromate solution, 20 ml concentrated sulfuric acid and 10 ml orthophosphoric acid.The solution was subjected to titration with ferrous ammonium sulphate using diphenylamine indicator.The solution was stirred to allow the dark violet color to change to green.
h) C:N ratio: The C:N ratio serves as an indicator to the degradation process.The reduction in the C:N ratio occurs due to degradation and release of gases [23].The growth of the earthworms results in more reduction of C:N ratio as they are negatively correlated with each other [30].It was calculated by the ratio of carbon to nitrogen value.

Cost economics:
The cost parameters in terms of unit cost of production and bene t-cost ratio govern the adoption level of the machinery [31].The cost parameters of conventional vermi-bed method were compared with smart vermicomposting bin for comparative evaluation.

Preliminary experimentation:
The initial nutrient content of Dal Lake aquatic weed and cow dung was measured (Fig. 4) and the materials were mixed in 1:1 proportion (40 kg each) in vermi-bed and smart vermicomposting bin.The nutrient content in terms of nitrogen, phosphorus, potassium, organic carbon and C:N ratio of Dal lake aquatic weed and cow dung was measured.

Statistical analysis:
The experiments were organized as per the plan of the experiment and statistically analysed by CRD (completely randomized design) to determine main, interaction effect and signi cant differences between treatment means.All the experiments were replicated thrice.The measurements were carried out at 5 % level of signi cance.

Variation in pH:
The pH value of the vermicompost prepared from Dal lake aquatic weed with 10 days turning frequency witnessed a change from 7.92 to 7.66 in 60 day's degradation duration, Fig. 5.In case of 20 days turning frequency, the pH decreased from 7.96 to 7.72 in the same degradation period.When the dal lake aquatic weed was degraded in smart vermicomposting bin with 10 and 20 days turning frequency, the pH decreased from 7.43 to 7.04 and 7.54 to 7.07 at 60 days degradation period.[32] recorded a pH reduction from 8.51 to 7.49 in degradation of water hyacinth through the process of vermicomposting.The reduction in the pH during vermicomposting may be attributed to the release of organic acids and production of carbon dioxide [33,34].The statistical analysis depicted that turning frequency and degradation period signi cantly (p<0.05) in uencing the pH value with the help of analysis of variance (ANOVA).
3.2 Change in electrical conductivity: The electrical conductivity of the Dal weed in conventional vermibed with 10 and 20 days turning frequency increased from 0.67 to 0.82 dS m -1 and 0.62 to 0.76 dS m -1 in 60 days degradation period, Fig. 6.The increase was mainly due to rapid degradation of the Dal weed owing to presence of su cient moisture in the stem of Dal lake aquatic weed.In smart vermicomposting bin, the electrical conductivity varied from 0.68 to 0.83 dS m -1 and 0.67 to 0.78 dS m -1 in 10 days and 20 days turning frequency and 60 days degradation duration.In general, the electrical conductivity of the Dal weed with 10 days turning frequency in both vermi-bed and smart vermicomposting bin showed better attributes than 20 days turning frequency.The increase in electrical conductivity [35,36] may be due to the release of soluble salts (nitrates, phosphates) and inorganic ions [37]], suggesting that vermicomposing might have transformed insoluble salts into soluble ions [38].The results were signi cantly (p<0.05) in uencing the electrical conductivity of the vermicompost.

Nitrogen content:
The bolstering of available nitrogen content [14] is one of the main parameter to decide the e cacy of the vermicomposting process.The data revealed that available nitrogen content increased from 8.27 to 9.62 g kg -1 and 8.2 to 9.53 g kg -1 with 10 days and 20 days turning frequency, 60 days degradation period in vermi-bed process.In smart vermicomposting bin, an increase of 10.63% and 10.99% increase in 10 days and 20 days turning frequency and 60 days degradation period, Fig. 7a.The increase in nitrogen content may be due to the conversion of insoluble nitrogen into soluble form by the activity of microorganisms present in the substrate [34,39].The statistical analysis proved the individual and interactive effect of turning interval and degradation period on nitrogen content at 5 % level of signi cance.

Available phosphorus:
The availability of available phosphorus maintains proper growth and augments the development phase of plant tissue.It has an important role in the synthesis of ATP, energy storage and transfer.Therefore, available phosphorus is also essential to determine the quality of the vermicompost and suitability of the vermicomposting process.The degradation of the Dal weed in vermibeds with 10 days turning frequency resulted in an increase in available phosphorus from 0.45 to 0.62 g kg -1 in 60 days duration.At 20 days turning frequency, the increase in phosphorus content was comparable with 10 days turning frequency.In smart vermicomposting bin, it was observed that available phosphorus increased from 0.5 to 0.63 g kg -1 and 0.48 to 0.6 g kg -1 in 10 and 20 days turning frequency and 60 days degradation period, Fig. 7b.The activity of the phosphorus solubilizing microorganisms in the gut of the earthworms can be held responsible for the rise in phosphorus content of the vermicompost prepared from aquatic weeds [40,41,42].The individual and interactive effects of turning frequency and degradation period were found to be signi cantly (p<0.05) in uencing the phosphorus content of the vermicompost.

Available potassium:
The role of available potassium in controlling the opening and closing of stomata, responsible for exchange of gases and photosynthesis is well documented.The available potassium content along with available nitrogen and available phosphorus determines the fertility status and potential of the process responsible for production of vermicompost.The turning frequency of 10 days and 20 days turning frequency resulted in an increase in available potassium content from 16.1 to 17.1 g kg -1 and 15.97 to 17.02 g kg -1 in 60 days degradation period.Fig. 7c.In smart vermicomposting bin, the potassium content increased from 17.36 to 19.12 g kg -1 to 16.56 to 18.18 g kg -1 in 10 and 20 days turning frequency and 60 days degradation period.The rise in available potassium level of the vermicompost was mainly due to decomposition of organic matter and potassium rich substrate [42,43].
The individual treatment was signi cantly (p<0.05) in uencing the potassium content of the vermicompost.
3.6 Organic carbon: Carbon is a major component of the building blocks of the living organisms [49].The availability of organic carbon maintains soil structure and stimulates the growth of microorganism.In general, the carbon content decreases [37] with the increase in turning frequency, Fig. 8.The carbon content decreased from 32.0 to 27.5 % with a mean value of 29.6 % in 10 days turning frequency and 60 days degradation period in vermi-bed process.In 20 days turning frequency, the organic carbon reduced from 32.2 to 28.8% with a mean value of 30.59 % in same degradation period.The smart vermicomposting bin resulted in the reduction in organic carbon from 30.88 to 26.25 % and 31.5 to 27.09 % in 10 days and 20 days turning frequency and 60 days degradation period.The organic content of 18.28, 16.24 and 14.22 % was recorded in 20 th day, 40 th day and 60 th day in the degradation process [50].
The release of the gases in the form of CO 2 during the degradation of organic matter might have resulted in the decrease in the carbon content [4,44,45,46,47].The statistical analysis proved that interaction of all the treatment combination has signi cant (p<0.05)effect on the carbon content. .Also, the earthworms were protected from other predators in smart vermicomposting bin in comparison to vermi-bed system.
[30] concluded that C:N ratio is negatively correlated with metabolic growth of earthworms.The C: N ratio of Dal weed was found to lie within the optimum range of 20:1 or lower.The interaction effect of substrate and duration was found to have signi cant effect on C: N ratio at 5 % level of signi cance.
3.8 Cost parameters of vermi-bed and smart vermicomposting bin: The analysis of the cost parameters revealed that the cost of fabrication of smart vermicomposting bin was Rs. 10,625 with production rate of 56 kg at one point of time.The bene t cost ratio ( rst year) of vermi-bed and smart vermicomposting bin was 1.25 0.48.In the second year, it was observed that bene t cost ratio of smart vermicomposting bin was higher than vermi-bed for same production rate.The rate of vermicompost production was Rs. 13 per kg in vermi-bed method and Rs. 13 per kg in smart vermicomposting bin, Table 4.

Conclusion
Conclusion: The dal lake aquatic weed was degraded in conventional vermi-bed and smart vermicomposting bin with 10 and 20 days turning frequency for 60 days degradation period.
When the dal lake aquatic weed was degraded in smart vermicomposting bin feeding hopper, chopping section, degradation chamber and harvesting gate, the pH was 7.04, electrical conductivity 0.83 dS m -1 , available nitrogen 11.03 g kg -1 , available phosphorus 0.63 g kg -1 , available potassium 19.12 g kg -1 , organic carbon 26.25 % and 16.31 C: N ratio.
The bene t cost ratio of vermi-bed method was higher than smart vermicomposting bin in the rst year.However, it shifted towards smart vermicomposting bin in second year (1.78 > 1.59).
The unit cost of production was Rs. 20 per kg with vermi-bed method and Rs. 13 per kg with smart vermicomposting bin.
The major limitation of the study lies in adjusting the speed of the mixer in smart vermicomposting bin so as to reduce the mortality rate and sustain the degradation period.
The study can be instrumental in leveraging towards the involvement of mechanical interface (smart vermicomposting bin) in vermicomposting to reduce the dependence on land, labour and degrade the organic materials in shortest possible time.

Declarations Figures
Page 16/  Procedural methodology in the vermi-bed vermicompost production Smart vermicomposting bin (Image reproduced from [2] Page 18/22    Change in organic carbon (%) with treatment combinations in vermi-bed (conventional) system Change in C: N ratio with treatment combinations in vermi-bed (conventional) system

3. 7 C
: N ratio: C: N ratio indicates the maturity of the vermicompost[32] and possesses an eminence in de ning the effectiveness of the vermicomposting process[48].A C: N ratio ≤ 20:1 signi es nutrient composition and stability of vermicompost.The Dal weed witnessed a diminution in C: N ratio from 25.1 to 18.1 with turning frequency of 10 days in 60 days degradation period in vermi-bed process.In 20 days turning frequency, it reduced from 26.03 to 19.09 in same degradation period.The involvement of smart vermicomposting bin resulted in the reduction in C:N ratio from 21.79 to 16.31 and 22.82 to 17.27 in 10 days and 20 days degradation period in 60 days degradation period, Fig.9.The decrease was more prominent with smart vermicomposting bin as the repeated and uniform turning might have accelerated the microbial growth and resulted in the reduction in shortest possible time[18]

Table 3 :
Measurement and signi cance of performance parameters for vermicomposting

Table 4 :
Cost economics of vermi bed and smart vermicomposting bin