Question

What is another way nitrogen is added back into the atmosphere BESIDES animal waste, but is too unreliable to count on?

Answer 1

Answer:

Plant and animal wastes decompose, adding nitrogen to the soil. Bacteria in the soil convert those forms of nitrogen into forms plants can use. Plants use the nitrogen in the soil to grow. People and animals eat the plants; then animal and plant residues return nitrogen to the soil again, completing the cycle.