Most of the man-made nitrogen fertilizer ever produced has been applied to fields in the last quarter-century.
Artificial nitrogen washes in drainage water from almost every field in the world. It is as ubiquitous in water as man-made carbon dioxide is in the air. It is accumulating in the world’s rivers and underground water reserves, choking waterways with algae and making water reserves unfit to drink without expensive clean-up.
Of 80 million tons spread onto fields in fertilizer each year, only 17 million tons gets into food. The rest goes missing, washing into ecosystems. This is partly because the fertilizer is wastefully applied, and partly because the new green-revolution crops developed to grow fat on nitrogen fertilizer are also wasteful of the nutrient. The nitrogen efficiency of the world’s cereals has fallen from 80 percent in 1960 to just 30 percent today.