Synthesis and characterization of potassium nanofertilizer from vermiwash

Introduction

Nanofertilizers are the fertilizers having particle size of less than 100 nm. Its smaller sizes makes it possible to entry into the plant system through hydathode, stomata and cell wall of the plant. Nanofertilizers application can supply nutrients to the plants in a gradual and controlled manner. They also have the ability to minimize nutrient losses through leaching, volatilization, and avoiding rapid changes in their chemical nature (Raliya et al., 2017) [16] . Nanoparticles can hold a lot of nutrients because of their large surface area and release it gradually so that the crop can absorb the nutrients it needs without experiencing any negative side effects from the specific fertilizer applications (Gupta et al., 2020) [9] . There is extremely little literature on nano-fertilizer technology, despite the fact that it is a very novel technology. Although numerous disciplines fall under the umbrella of agriculture, the speed of progress is moderate, despite the fact that nanotechnology in agriculture has accelerated over the past ten years with a plethora of public financing (De Rosa et al., 2010) [6] . Therefore, it contributes to boosting crop output, reducing fertilizer waste, and safeguarding the environment by enhancing the bioavailability and uptake of minerals (Tapan et al., 2010, Tarafdar et al., 2014, Dimkpa Bindraban, 2016) [20,21,7] . For high crop yields and soil regeneration, nanofertilizers (NFs) have emerged as a possible smart fertilizer substitute. To feed the huge world population, there will be more pressure on the resources like land and water which are not extendable. The increasing population caused the heavy use of fertilizer for supplying necessary nutritional food. The intensive use of chemical fertilizers has different possible side effects on the human and environment. After all various fertilizers focused on plant nutrition, the NFs found and studied as a way to boost nutrient dosage and plant nutrition along with healthy food, as compared with traditional fertilizers. NFs have gained the attention of agricultural engineers, environmentalists, and soil scientists due to their power to increase crop yields, positivity to soil fertility, trimming down pollution, and mark a burgeon Eco to flourish microorganisms. In recent years K nanofertilizer was prepared from various plant extracts viz. banana peel (Hussein et al., 2019, Franck et al., 2020) [11,8] Morus alba plant leaf extract (Sheoran et al.

2021) [19] and through chemical synthesis Sebastian et al. (2024) [18] . K nanofertilizer can also be prepared from Vermiwash which is a byproduct produced during vermicompost preparation. Vermiwash is considered as a liquid fertilizer due to the presence of macro nutrients, micronutrients and existence of humic acid and fulvic acid in it (Guteirezz Miceli et al, 2008) [10] . But releasing the vermiwash as such into the environment, especially if it is near ground water source will cause pollution (Katheem Kiasuddin et al. 2016) [14] . Transforming this organic product into a valuable resource like K nanofertilizer and its application in agriculture, will boost agricultural productivity, thereby satisfying the needs of growing population for food security. To the best of our knowledge synthesis of K nanofertilizer from vermiwash was the novel approach that we have initiated. With this viewpoint the present study was carried out with an objective to synthesize and characterize K nanofertilizer from vermiwash and to study its effect on germination percentage of Toria crop.

Materials and methods Preparation of nanofertilizer from vermiwash

Vermiwash collected from vermicompost tanks existed at Krishi Vigyan Kendra, Barpeta was filtered through a funnel using filter paper to get rid of any particles. One hundred milliliters of vermiwash were combined with 400 milliliters of 0.1 M KCl. After 24 hours of heating the mixture to 70 °C, the precipitate was segregated by centrifugation for five minutes at 6,000 rpm. The nano particles were dried in an oven set at 80 °C after being five times cleaned with ethanol and double-distilled water (Arslan et al. 2022) [3] and were used for study of relevant properties.

Analysis of extract

The alkaline extract of the vermiwash was digested with concentrated nitric acid at elevated temperatures. The resulting solution was digested and the extract contents were used for determination of the N, P, K, Na, Ca and Mg contents by following the procedure described by Jackson (1973) [12] . The levels of micronutrients such as iron, copper, zinc, boron and manganese were determined as described by Layne (1975) [15] . The crude fat content, crude protein content, Tryptophan and ash content were analysed by using the standard methods described in Association of Official Analytical Chemists (AOAC 1995).

Characterization of synthesized fertilizer

The size distribution and zeta potential of the synthesized fertilizer were determined by DLS technique using the instrument Zetasizer version 7.13, Malvern. The physical dimensions of the potassium nanoparticles were determined by TEM (JEM-2100 PLUS (HR), JEOL). This instrument is capable of high resolution EELS (Electron Energy Loss Spectroscopy) for analysis of the bonding state at the nanometer scale. The drop coating method was employed for sample preparation. A drop of suspension containing nanoparticles was placed on the carbon-coated copper grids and dried overnight under vacuum desiccators. The sample was placed on a specimen holder and characterized.

Nanofertilizer application in agriculture

Toria seeds (variety. TS 38) were sown under green house on 10/11/2024 and were fertilized with (5, 10, 15 and 20) ml/l of K nanofertilizer extracted from vermiwash. The germination rate was determined after one week. The soil used for the study was sandy loam with pH 6.3 and electrical conductivity 0.01 dS/m. Simple correlation test was done to measure the correlation between applied extracted fertilizer and germination rate of the crop.

Results and Discussions

The total N, P and K contents of K nanofertilizer extracted from Vermiwash (V) were 1.45%, 0.79% and 2.41%, respectively, while the contents of Ca, Mg and Na were 0.11%, 0.08% and 0.03%, respectively (Table 1). The micronutrient contents like Fe, Cu, Zn, B and Mn were found to be 15.2 ppm, 0.05 ppm, 0.08 ppm, 0.07 ppm and 0.04 ppm, respectively. The organic compound contents like carbohydrate, crude fat, crude protein, tryptophan and ash content were determined to be 1.2%, 0.07%, 15.31%, 0.09% and 0.08%, respectively (Table 1). The percent increase of N, P, K, Ca, Mg and Na were 1.04%, 0.95%, 0.98%, 0.04%, 0.06% and 0.02%, respectively, whereas, the micronutrients like Fe and B contents were raised by 3.85 ppm and 0.03 ppm, respectively. On the other hand, the contents of Cu, Zn, and Mn were increased by 0.02 ppm. Similarly, the percent increase of carbohydrate, crude fat, crude protein, tryptophan and ash content were 0.34%, 0.03%, 2.98%, 0.05% and 0.01%, respectively. Among the macronutrients, K content was found to be highest (2.42%) in the vermiwash extract. Use of K rich inputs like Banana stems during the production of vermiwash might increased the amount of K in the vermiwash extract. Higher amount of K content compared to nitrogen, phosphorus and other nutrients in Vermiwash were also observed by Carlos et al. (2008) [4] . Cabilovski et al. (2023) [5] reported that vermicompost leachate i.e Vermiwash consist of many nutrients that are beneficial to plant growth.

Zeta sizer

The size distribution by intensity report through Zeta sizer gives a vivid picture about the average size of the K nanoparticles present and intensity of nano size particles in the synthesized nanofertilizers. The average size of K nanoparticles in Vermiwash determined by the instrument Zeta Sizer, was found to be 34.6 nm with 100 % intensity and Poly dispersity index (PDI) value 0.381 (Fig. 1), showing a high degree of particle monodispersity (Sheoran et al. 2021) [19] . The zeta potential of the extracted fertilizer was observed to be high (-31.9 mV) because of its smaller size. The high zeta potential of the particles prevents aggregation, resulting in a stable solution (Sheoran et al. 2021) [19] . It was seen from the above findings, in general, that the techniques used for synthesis of nano-fertilizers were adequate and successful. The results of Hussein et al.

(2019) [11] were also found to be in line in the present study.

Transmission Electron Microscopy (TEM)

The TEM analysis of the obtained vermiwash extract by using KCl as extracting agent shows that nanospherical structure particles were obtained with size range from 20 to 28 nm (Fig: 2). The presence of both citric acid and urea was responsible for the conversion to nanostructure because citric acid combines with minerals to generate mineral citrate, and urea was required to transport this mineral citrate in the nanoform. Similar type of findings were also observed by Hussein et al. (2019) [11] and Sheoran et al.

(2021) [19] . [17,13] . In addition metal ions present in the nanofertilizer mix with organic components to create chelates which makes the plant resistence to precipitation loss (Aboul-Enein et al. 2016) [1] .

Acknowledgement

AcknowledgementThe authors thank Sophisticated Analytical Instrumentation Centre (SAIC), Institute of Advanced Study in Science and Technology (IASST), Guwahati (under the Department of Science & Technology, Government of India) for TEM analysis.

References

1. Aboul-Enein AM, Salama ZA, Gaafar AA, Aly HF, Abou-Elella F, Habiba AA. Identification of phenolic compounds from banana peel (Musa paradisiaca L.) as antioxidant and antimicrobial agents. J Chem Pharm Res. 2016;8(4):46-55.
2. AOAC. Official methods of analysis. 15th ed. Arlington, VA: Association of Official Analytical Chemists; 1995.
3. Arslan H, Gonca S, Isik Z, Ozdemir Z, Yalvac M, Dizge N, et al. Iron oxide nanoparticles synthesis from vermicomposting leachate and its antioxidant properties. Front Mater. 2022;9:912066. doi:10.3389/fmats.2022.912066.
4. Carlos GGR, Dendooven L, Antonio GMF. Vermicomposting leachate (Worm Teas) as liquid fertilizer for maize (Zea mays L.) forage production. Asian J Plant Sci. 2008;7(4):360-367. doi:10.3923/ajps.2008.360.367.
5. Cabilovski R, Manojlovic MS, Popovic BM, Radojcin MT, Magazin N, Petkovic K, et al. Vermicompost and vermicompost leachate application in strawberry production: Impact on yield and fruit quality. Horticulture. 2023;9(3):337. https://doi.org/10.3390/horticulturae9030337.
6. De Rosa MC, Monreal C, Schnitzer M, Walsh R, Sultan Y. Nanotechnology in fertilizer. Nat Nanotechnol. 2010;5:91.
7. Dimkpa CO, Bindraban PS. Fortification of micronutrients for efficient agronomic production: A review. Agron Sustain Dev. 2016;36:7.
8. Franck KN, Eustache NM, Erick KS. Synthesis of a potassium fertilizer from banana peels and its fertility effect on onion growth and ripening in Lubumbashi. Int J Recent Eng Res Dev. 2020;5(10):10-21.
9. Gupta C, Prakash D. Effect of nanofertilizers on soil microflora. Ann Plant Sci. 2020;9(5):3846-3859.
10. Gutierrez-Miceli F, Garcia-Gomez R, Rincon-Rosales R, Abud-Archila M, Maria-Angela O, Cruz M, et al. Formulation of a liquid fertilizer for sorghum (Sorghum bicolor L. Moench) using vermicompost leachate. Bioresour Technol. 2008;99(14):6174-6180. doi:10.1016/j.biotech.2007.12.043.
11. Hussein HS, Shaarawy HH, Hussein NH. Preparation of nano-fertilizer blend from banana peels. Bull Natl Res Cent. 2019;43:26.
12. Jackson ML. Soil chemical analysis. New Delhi: Prentice Hall of India Pvt. Ltd.; 1973.
13. Lv J, Christie P, Zhang S. Uptake, translocation, and transformation of metal-based nanoparticles in plants: recent advances and methodological challenges. Environ Sci Nano. 2019;6(1):41-59.
14. Katheem Kiyasudeen S, Ibrahim MH, Quaik S, Ismail SA. Introduction to organic wastes and its management. Appl Environ Sci Eng Sustain Future. 2016:1-21. doi:10.1007/978-3-319-24708-3.
15. Layne EE. Methods in enzymology. 1975;3:447.
16. Raliya R, Tarafdar JC, Biswas P. Enhancing the mobilization of native phosphorus in the mung bean rhizosphere using ZnO nanoparticles synthesized by soil fungi. J Agric Food Chem. 2016;64(16):3111-3118.
17. Sadak MS, Orabi SA. Improving thermo tolerance of wheat plant by foliar application of citric acid or oxalic acid. Int J ChemTech Res. 2015;8(1):111-123.
18. Sebastian A, Devika PS, Nair PP, Devadas VS. Green synthesis of potassium-infused nitrogenous nanofertilizer for enhanced plant growth. Chem Pap. 2024;78:1481-1492.
19. Sheoran P, Goel S, Boora R, Kumari S, Yashveer S, Grewal S. Biogenic synthesis of potassium nanoparticles and their evaluation as growth promoter in wheat. Plant Gene. 2021;27:100310.
20. Tapan A, Biswas A, Kundu S. Nano-fertiliser-a new dimension in agriculture. Indian J Fert. 2010;6:22-24.
21. Tarafdar J, Raliya R, Mahawar H, Rathore I. Development of zinc nanofertilizer to enhance crop production in pearl millet (Pennisetum americanum). Agric Res. 2014;3:257-262.