Nitrogen-15, a stable isotope of nitrogen and an essential plant nutrient, is used to determine the fertilizer use efficiency of crops. It is also used to quantify the amount of nitrogen that crops can acquire from the atmosphere through a process known as biological nitrogen fixation. This helps to reduce the application of purchased nitrogen for crop and livestock production, and can result in very significant cost-savings in agriculture. Nitrogen-15 is also used to assess integrated soil-water management practices to optimize crop productivity. It can be applied to various vital crops including rice and sugar cane. Read more.