Are the Enrichment Nutrient Feasible to the Vermicomposting Eciency For Water Hyacinth (E. Crassipes)?

In eutrophic environments, aquatic weeds reproduce quickly and occupy large areas, preventing multiple uses of water resources. The use of the biomass of these plants in vermicomposting represents a sustainable alternative. The enrichment of macrophyte biomass during vermicomposting was tested using inorganic NPK solution (1.75% and 3.5%) and organic solution (0.25 g/L and 0.5 g/L) to improve the quality of the compound. Biomass consumption increased as the experiment progressed, reaching the highest values at the end. The experiment without worms remained stable. The influence of E. fetida individuals the vermicomposting process of water hyacinth will depend nutrient addition. The additions improved subtly the compost quality and the consumption of biomass, besides its low-cost, easily obtained and applicable treatment. It does not have the necessary requirements for its use as a fertilizer. However, we suggest the use in association with other fertilizers, adding moisture and structuring to the soil.

Due the high biomass production in eutrophic systems, the use of macrophyte biomass represents an ecological and sustainable alternative economic use of these vegetables. One of the main characteristics of the treatment is the possibility of using practically any organic material and the formation of a nutritious compound that can be used for fertilization. It is justify especially once weed water hyacinth as a source of macronutrients as nitrogen, phosphorus and potassium which improve the soil fertility (Kumari et al., 2021) However, there are few sustainable techniques applied, such as physical, chemical and biological methods that have undesirable impacts (e.g. contamination by herbicides) (Thomaz, 2002). The use of excess biomass as a raw material for vermicomposting thus consists of a possibility of reducing an environmental problem by applying this biomass in sustainable techniques (Najar, 2017). Composting consists in a treatment of waste regulated by microbial decomposition, featured by the oxidation of organic matter. A process similar to composting is vermicomposting, which is distinguished by the use of mesofauna, especially Eisenia fetida (Oligochaeta, Lumbricidae). The process of composting is facilitate by the combined action of earthworms with that of flora present in your digestive tract. During composting, part of the organic matter is mineralized in carbon dioxide, ammonia and water, while the other part is transformed into humic substances (Valente et al., 2009). Hamer (2004) observed that the positive effects of adding different organic substrates are often related on the mineralization of organic carbon in the soil. Blagodatskaya et al. (2007) indicated that the addition of carbon-rich compounds can strongly change the turnover of native organic matter, causing the priming effect. As stated by Tótola & Chaer (2002), a high-quality soil has intense biological activity that can be defined by microbiological indicators, therefore, the priming effect is beneficial to the mineralization process and increased soil quality.
Addition of exogenous organic matter in the soil can cause intensification or delay in the decomposition of organic matter (Chen et al., 2014). Decomposition requires a sequential breakdown of a variety of substrates (such as: waxes, phenols, lignin, and cellulose). The priming effect overcomes this limitation by availability of more nutrients from fresh organic matter. Kaspari et al. (2008) exemplifies this statement when describing the decomposition of litter, in which the decomposing microorganisms are presented as the main limiting factors. In that case, the provision of a greater amount of nutrients would accelerate this process since enzymes produced by different microbes are required. Laskowski & Berg (2005) showed that nitrogen-rich leaves decompose more quickly when compared to nitrogen-poor leaves. Incorporation of inorganic and organic elements as an additional source of nutrients for priming effect may improve the quality of the vermicompost generated by macrophyte biomass. This addition can be exemplified in similar studies by adding additional sources of nutritious organic compounds in studies such as animal waste. It is common to add manure to manure in a combined treatment of both in the proportion of 50%. The experiment achieved total conversion of macrophyte biomass in 110 days. Ansari  This study aimed to study vermicomposting using the biomass of Eichhornia crassipes as a source of organic matter, aiming to evaluate the compound generated after the addition of organic and inorganic substance (glucose and commercial fertilizer NPK) in two concentrations each. The specific objectives were: (i) to evaluate the kinetics of macrophyte consumption by E. fetida; (ii) evaluate the quality of the humus formed from the vermicomposting by means of particles; (iii) identify whether the addition of a pre-activator (organic and inorganic) will increase the quality of the generated humus and (iv) evaluate the consumption of macrophyte biomass by E. fetida using mathematical modeling. This study had the hypothesis that the incorporation of both substances as an additional source of nutrients may improve the quality of the vermicompost generated in the macrophyte biomass by priming effect.

Assembly and preparation of vermicomposting experiment
Specimens of water hyacinth were collected manually at the Departmento de Botânica (DB) of the Universidade Federal de São Carlos (UFSCar). After collected, the macrophytes were manually washed in running water to remove aggregate debris.
All parts of the plant were used, which were cut after this process to facilitate the consumption. A portion of the specimens were kiln dried (ca. 50 ° C) until constant mass. This procedure allowed composing the proportions of biomass (dry and fresh -3:1).
The vermicomposting experiment occurred in three dark polypropylene boxes, previously cleaned, dried and stacked (total dimension: 32 cm long, 16 cm wide and 36 cm high). The system were composed of two digester boxes (total volume: 8 L) and a collection box (volume: 4 L). In the digester boxes a layer of ca. adaptation. Some standards must be followed so the vermicomposting reaches its objectives and, at the same time, corresponds to the tolerance standard of the present macrofauna. Therefore, it was sought to keep earthworms at 25ºC and 75% humidity (Venter & Reinecke, 1988). The added macrophytes must be in both fresh and dry form, with the addition of 10g of fresh biomass and 30g of dry biomass. At the same time, mini systems (n = 24 for each treatment) were set up to observe the consumption kinetics of macrophyte biomass. The mini systems were prepared with E. crassipes biomass and E. fetida individuals in the same proportion as the previously described in the system (1 g of fresh biomass, 3 g of dry biomass and 3 individuals of E. fetida). The mini system were dismounted weekly (following the same procedures described) and the consumption efficiency of E. crassipes biomass was calculated (Equation 1).
Experiments without earthworms (n = 24) and without treatment were also set up to allow a comparison between the consumption of biomass by the annelids and the Glucose treatment 0.5 g/L. The first addition was made after finishing its assembly, being added 100 mL of the solution in each system and 10 mL in each mini system. The following applications were of 50 mL and 10 mL respectively for system and mini system in the first week, 25 and 10 in the second week and 10 and 5 in the third week.
To monitor the abiotic conditions (pH, electrical conductivity) in the system, weekly samples were taken, in replica, of the vermicompost and monitored the following variables: temperature, humidity, pH and electrical conductivity (EC). The temperature was obtained by measuring the mercury thermometer.

Statistical analysis
Differences in the mean values of variables pH, EC, E2/E3, E4/E6 and humic substances between treatments and days of colonization were compared using Two-way ANOVA without replications, and significant differences were considered with 95% confidence intervals (p < 0.05). Changes of pH, EC, E2/E3, E4/E6 and humic substances values along the days of the experiment were analyzed by the Multiple Linear Regression analysis. These variables were used as dependent variables and compared by analysis of variance (ANOVA), with significant differences considered at 95% confidence intervals (p < 0.05). Spearman rank correlation analysis was used to analyze the associations between the significant variables in humic substance production. The significances of the associations between the variables were analyzed using the correlation coefficients, and the 95% confidence intervals were considered (p < 0.05).

Biomass consumption efficiency
The efficiency of biomass consumption in vermicomposting was not an important indication of feasibility of using macrophyte biomass, however, showed the effectiveness of its use as a sustainable alternative. The kinetics consumption observed by the experiments in the mini systems showed similar patterns in all treatments: an efficiency of less than 50% in the initial weeks. Until the fourth week of the experiment, the efficiency values remained between 50% and 75%. It was also possible to observe a sharp increase in biomass consumption of all treatments throughout the experiment, especially at the end, reaching values around 80% (Figure 1).

The comparative analyses of initial and final biomass and abundance of E. fetida
showed that the Control, NPK 1.75% and 3.50 % treatments concentrations showed significant reduction of biomass at the end of the experiment. The same result was observed for the number of individuals only in the inorganic nutrient treatments (Table   3). The comparative analysis between the vermicomposting efficiency treatments with presence and absence of the earthworms, showed that the Control treatment followed by NPK 3.50% presented significantly higher average efficiencies than the other treatments (F = 16.31, p < 0.001, Figure 2). The treatments with added organic nutrients showed less variation in average efficiency values. The treatments also differed significantly over the total vermicomposting period (F = 3.40, p < 0.0001). The influence analysis of the variables showed that the efficiency of vermicomposting was significantly positive over the long period ( Figure 3) contradicting to the final number of E. fetida (Figure 4). Concerning to this, we could infer that probably the efficiency of water hyacinth received the action mainly by development of microbiota along the vermicomposting experiments.
Glucose 0.50 g/L presented the highest consumption coefficient (0.99 wt -1 ) despite having the lowest accumulated consumption among the observed treatments (47.5%).
The consumption coefficient for the organic treatments were much higher than the others, reaching maximum values (0.95 and 0.99 wk -1 ).

Fertility
The results of the fertility tests for the composts formed by vermicomposting macrophytes are described in   with both inorganic (NPK) and organic (glucose) compost caused a subtle increase in the quality of the compost formed. The compost, however, can work as an aggregator to the soil promoting moisture increase and providing greater soil structuring, as well as in association with another fertilizer. The composts enriched with glucose were superior in terms of biomass consumption efficiency, which were 51.5% and 40.5% higher than the average of the treatments with NPK. The addition of glucose has the benefits of being easy to obtain and low cost, being a viable alternative for improving production through a sustainable alternative for the use of surplus biomass and transformation into a fertilizer applicable in other local productions. We suggest that future studies test the application of this technique on a large scale.

Conclusion
Vermicomposting using macrophytes represents a sustainable alternative for the use of this biomass. The addition of both organic and inorganic compounds proved to be adequate for this process, contributing to an increase in efficiency in the consumption of biomass and a subtle improvement in the fertility of the compost formed. The addition of glucose is a low-cost, easily obtained and applicable. Although the addition shows an increase in compost quality, it does not have the necessary requirements for its use as a fertilizer. However, we suggest the use in association with other fertilizers, adding moisture and structuring to the soil. The datasets generated and/or analysed during the current study are available in the "Repositório Institucional UFScar" repository, available in https://repositorio.ufscar.br/.