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Atmospheric reactions and slow geological processes controlled Earth's earliest nitrogen cycle, and by ~2.7 billion years ago, a linked suite of microbial processes evolved to form the modern nitrogen cycle with robust natural feedbacks and controls. Over the past century, however, the development of new agricultural practices to satisfy a growing global demand for food has drastically disrupted the nitrogen cycle. This has led to extensive eutrophication of fresh waters and coastal zones as well as increased inventories of the potent greenhouse gas nitrous oxide (N(2)O). Microbial processes will ultimately restore balance to the nitrogen cycle, but the damage done by humans to the nitrogen economy of the planet will persist for decades, possibly centuries, if active intervention and careful management strategies are not initiated.


In trying to feed our growing population, we now add twice as much nitrogen to the soil (after chemically fixing it to make fertilisers) as microbes fix from the atmosphere. Human activity has skewed the balance in the earths nitrogen cycle. But how...
Human activity has skewed the balance in the earth’s nitrogen cycle. But how did the modern nitrogen cycle evolve? A recent review published in Science tries to answer that question and make suggestions about the future.How did the nitrogen cycle of the...