Humans add about 150,000,000 tons of fixed nitrogen to the biosphere each year, primarily:

Question

Quizplus · Accepted Answer

The primary source of fixed nitrogen added to the biosphere by humans is through the use of fertilizer in agriculture. Fertilizer is typically made up of nitrogen, phosphorus, and potassium, and is added to soil to improve plant growth and yield. The use of fertilizer has increased dramatically over the past century as a result of advances in agriculture and population growth, leading to a significant increase in the amount of fixed nitrogen in the biosphere. While nitrogen emissions from burning fossil fuels and industry also contribute to the amount of fixed nitrogen in the biosphere, they are not the primary source.

Humans Add About 150,000,000 Tons of Fixed Nitrogen to the Biosphere