The most common method of earthing is known as the direct burial method. This involves simply driving a rod into the ground and attaching a wire to it. This is the cheapest method of earthing, but it is also the most labour intensive.
Another popular method is known as the plate method. This involves placing a metal plate in the ground and attaching a wire to it. This method is cheaper than the direct burial method, but it is still quite Laboure intensive.
The third method is known as the chemical method. This involves adding a chemical to the soil that will react with the metal to create an electrical connection. This method is the most expensive, but it is also the easiest to do.
So, which is the cheapest method of earthing? It really depends on your situation. If you have the time and the labour available, then the direct burial method is the cheapest. If you want a cheaper and easier method, then the chemical method is the best choice.