of the Minimum - Liebig's Law
von Liebig, generally credited as the "father of the fertilizer
industry", formulated the law of the minimum: if one crop nutrient is
missing or deficient, plant growth will be poor, even if the other
elements are abundant.
Liebig likens the potential of a crop to a barrel with staves of unequal length. The capacity of this barrel is limited by the length of the shortest stave (in this case, phosphorus) and can only be increased by lengthening that stave. When that stave is lengthened, another one becomes the limiting factor.