Living on air From air to plant nutrient Producing nutrient nitrogen We are surrounded by an endless amount of nitrogen. Almost 80% of the Earth’s atmosphere is made of gaseous nitrogen, known as atmospheric nitrogen or N2. We breathe it in, but our bodies cannot absorb it. It’s as if we were bobbing around in a boat on an immeasurable ocean, surrounded by an endless amount of water that we’re unable to drink. To make atmospheric nitrogen suitable for consumption, it has to be “fixed.” The process of fixation produces nutrient nitrogen, which serves as a plant nutrient. In nature, nitrogen is fixed both in the atmosphere and in the soil. Lightning strikes, for example, will cause some fixation of atmospheric nitrogen, with rain then carrying the result, nutrient nitrogen, to the soil. When bacteria in the soil work together with certain plants, especially clover, they also fix atmospheric nitrogen. Once again, the resulting nutrient nitrogen ends up in the soil. Plants absorb this nitrogen and use it to synthesize proteins and other substances, making it available to animals and people who eat the plants. I 9
12 Online Touch Home