The loss of fertilizer shipments coming from the Persian Gulf as a result of the Iran war got me thinking about the chemist Justus von Liebig, a prominent 19th century proponent of the mineral theory of plant nutrition. Liebig is the popularizer of what is now known as Liebig's Law of the Minimum. The law states that the least available essential nutrient limits the growth of plants. This means once a grower runs out of one essential nutrient, adding extra of others will not make up for the lack of the one that is limited.
Liebig's eponymous law is about to assert itself in a big and distressing way in the coming growing season. That's because the Persian Gulf region supplies 36 percent of the world's urea (a form of nitrogen fertilizer), 29 percent of its anhydrous ammonia (another form of nitrogen fertilizer), 26 percent of diammonium phosphate and 13 percent of monoammonium phosphate.
Just to review a little high school biology, nitrogen, phosphorus and potassium are primary nutrients that cannot be obtained from the air or water and must come from the soil. (With regard to nitrogen, legumes such as soybeans are an exception in that they can fix nitrogen from the air for use in the plant.) Adding these primary nutrients to the soil improves the quality and quantity of plant growth. Huge of amounts of two of the three primary nutrients mentioned above are no longer flowing out of the Persian Gulf.