All plants need nitrogen to survive, but it is naturally available to them in only limited supplies. in 1909, engineers developed a process to make nitrogen available to plants by synthetically producing the chemical ammonia. once produced, ammonia could be used as a fertilizer for crops around the world to its nitrogen content. the process that the engineers developed is still used today. it makes use of the reaction between nitrogen gas and hydrogen gas at very high pressures. nitrogen gas is the most abundant gas in the atmosphere and is widely available. hydrogen gas needs to be made from the methane found in natural gas. natural gas is a fossil fuel that can be extracted from underground reserves. what natural resources are used to make ammonia fertilizers? 1)atmospheric nitrogen 2)ammonia 3)natural gas 4)hydrogen gas