INTRODUCTION Nanotechnology will have a significant impact on our country's overall development. Nanotechnology is the fabrication, manipulation, and application of submicron objects, particularly those between 1 and 100 nanometers in size. Nanotechnology will allow for the production of high-quality products at a low cost and in a short amount of time. It is commonly referred to as a generic technology that provides better-built, safer, longer-lasting, low-cost, and smart products for use in the home, communications, medicine, agriculture, and the food industry, among other applications. Excessive use of conventional fertilizers in modern agriculture has resulted in several serious issues such as soil degradation, loss of soil organic matter and carbon content, and increased soil compaction. To overcome this problem use of nano fertilizers would be the solutions. But among various chemical, physical and biological methods of synthesis, green method for synthesizing nanoparticles with plant extracts is simple, convenient, environment friendly and require less reaction time. Nanomaterials made using eco - friendly green synthesis method have the potential to improve agriculture's fertilization process. Furthermore, they reduce the amount of harmful chemicals released into the environment. As a result, this technology aids in the reduction of environmental pollutants, resulting in a more sustainable approach. Magnesium is a key component of chlorophyll, which helps plants absorb light during photosynthesis. Magnesium is necessary for phosphate metabolism and acts as a phosphorus carrier in plants. Photosynthesis, as the central process for crop production, is influenced by the Mg status of the plant in several ways. High light interception by the light harvesting complexes (LHCs) attached to photosystems I and II is required for efficient carbohydrate formation (PSI, PSII). Use of Nano magnesium fertilizers instead of conventional fertilizers has additional advantages because of its unique physicochemical behaviors such as outstanding refractive index, economically feasible with high surface are resulting in greater advantages. Among the chemical, physical and biological methods of synthesis of nano magnesium particles the biological approach would be ecofriendly and easy to synthesize the particles. Hence this review help us to find the best method in synthesizing the nano magnesium particles that can be used as a fertilizer source or other applications. Different methods of synthesis of nano magnesium fertilizer • There are mainly two method of synthesis of nano particles mainly the bottom up approach and top down approach 1. Bottom-up approach • A bottom-up approach is when a material is built up from the ground up, atom by atom, molecule by molecule, or cluster by cluster. • Assembling nanomaterials atom-by-atom or molecule-by-molecule (self-assembling) • This aims to combine smaller components into larger assemblies. • The bottom-up approach has the advantage of obtaining nanostructures with fewer defects and more uniform chemical compositions. 2. Top-down approach • Slicing or successive cutting of a bulk material to obtain nano-sized particles is referred to as a top down approach. • Breaking down larger materials physically or chemically to create nanoscale materials •These aim to make smaller devices by directing the assembly of larger ones. Physical method of synthesis Nano magnesium particles. Physical methods generate magnesium nanoparticles by causing material abrasion, melting, evaporation, or condensation with mechanical pressure, high-energy radiations, thermal energy, or electrical energy. These methods are advantageous because they produce uniform monodisperse nanoparticles and are based on a top-down strategy. Different physical method of synthesis such as ball milling, physical vapour deposition, molecular beam epitaxy, sputtering, laser ablation, electric arc deposition, etching, lithography among these few references are reported. Praditaet al., 2017 reported that synthesis of Nano magnesium can be done using spray pyrolysis using precursor as Mg(NO3)2.6H2O. Han Wang et al., 2015 reported that magnesium nanowires were prepared at 703 oK for 30 min in a high vacuum level of 104 Pa by physical vapor deposition method. For the preparation of nanoparticles, laser ablation in liquid has been considered an appealing technique. Tran X. Phuoc et al., 2008 studied that synthesis of Mg(OH)2, MgO, and Mg nanoparticles using laser ablation of magnesium in water and solvents and reported that particles were about 20–30 nm and particles with rod-like, triangular, and plate-like shapes were also observed. Chemical methods of synthesis of Nano magenesium particles. Different chemical methods followed in synthesis of Mg nanoparticles such as microemulsion technique, sol–gel method, temperature assisted synthesis polyol synthesis, hydrothermal synthesis, chemical vapour synthesis and plasma enhanced chemical vapour deposition technique are some of the most commonly used chemical methods for the synthesis of Mg nanoparticles. Tamilselvi et al., 2021 reported that Magnesium oxide nanoparticles can be synthesized by employing a simple sol-gel method using angelating agent using magnesium nitrate [Mg (NO3)] as precursor the average size of the synthesized nanoparticles is 12 nm. Microwave-assisted synthesis of Mg nanoparticles is another chemical method which is widely used. This method promotes uniform dispersion of small molecules and is both cost-effective and environmentally friendly. Gajengi et al. (2017) studied microwave mediated synthesis in the presence of benzylamine, which forms an intermediated complex of Mg(OH)2 due to the reducing agent's action. Selvam et al., (2011) synthesized microwave-promoted MgO nanoparticles in the presence of urea. They also studied that microwave mediated synthesis is less energy consuming than the traditional combustion synthesis method. Pei et al., 2010 reported low temperature assisted synthesis is easy and environmentally friendly approach of synthesis of Mg nanoparticles which can be used as fertilizer sources. Furthermore, Shimpi et al. (2009) reported synthesis of Mg nanoparticles using hydrothermal method at low temperature (155°C) is easy and synthesized particles were spherical in shape. Biosynthesis of Nano magnesium particles. For the past decade, scientists have been interested in producing Mg nanoparticles using biological methods. The use of fewer chemicals, cost-effectiveness, and environmental friendliness have all played a role in the evolution and importance of this field. Traditional chemical or physical methods of nanoparticle synthesis are less convenient, less cost-effective, and less environmentally friendly than green synthesis as reported by Das et al. (2017). Plants, bacteria, fungus, and algae are some of the biological substrates that are commonly used instead of chemical solvents and stabilisers to reduce the product's toxicity. In Biosynthesis approach the substrate used is either microorganism or plant extract. Plants are the most common biological substrate for Mg nanoparticles because they are cost-effective, environmentally friendly, easy to process, handle, and safer than microorganisms. Bandeira et al. (2020) reported that plant extracts acquired from various parts of the plants including root, bark, leaves, flowers, fruit pulp, peels etc. are used for synthesizing Mg nanoparticles. Singh et al. (2019) have reported that the biomolecules present in the plant extract are considered responsible for the reduction of of Mg2+ ions to Mg0 valency state.