Comment Re:Great, now what about phosphorous? (Score 4, Interesting) 187
I remember reading "Life's Bottleneck" by Issac Asimov. He calculates that if life expands and uses the elements in the entire crust of the earth, the phosphorus will be exhausted first, before carbon, nitrogen, or even trace elements like iodine and selenium. Phosphorus is life's bottleneck.
But there is a big difference between fertilizing with phosphorus and nitrogen. You only need to add phosphorus once, and then only enough annually to replace what is taken out with the crop, which is usually not much. It is a permanent addition to the soil. But the nitrogen is consumed and returned to the atmosphere as the plants grow and then decay. You need to replenish it every year, either with fertilizer or legumes.