Liebig’s law of the minimum – agricultural sciences since 1840
Anyone who wants to understand the growth of organisms cannot ignore Liebig's law of the minimum. Fortunately, what lies behind it is not particularly complicated: Everyone knows that humans, plants and animals need a number of nutrients – and are appropriately dependent on growth factors such as light and temperature. The law of the minimum focuses on these nutrients and growth factors. It says that of these nutrient bases, the one that inhibits growth (and thus also harvest yield) is the one that is too scarce, i.e. below the specific optimum quantity. This is also the case when all other nutrients and favorable factors are present in abundance. This scarcest resource is also known as the minimum factor.
Growth from the barrel
The illustrative model of the minimum law is the “minimum ton”. This buoy has staves of different lengths (each corresponding to a nutrient) and can only be filled to the height of the shortest stave. The other staves can be as high as you like, but the maximum possible filling height (which corresponds to the growth / crop yield) does not change.
Correctly, the law should actually be called Sprengel’s law of the minimum, because it was Carl Sprengel who first published it in 1828. Justus von Liebig popularized it in 1840 in an extended form.
In agriculture, Sprengel and Liebig's law of the minimum has played an important role since its discovery. It was even of immense importance in the middle of the 19th century, since at that time many soils in Central Europe were already depleted by overuse. The introduction of mineral fertilizers, which were produced in compliance with the minimum law, brought enormous increases in yield, which have increased five- to six-fold to this day.
It is not that simple after all
In practice, it was also shown that the connections are not quite as simple as illustrated in the barrel model. It quickly became clear that the minimum law did not apply uniformly under all conditions. It may well happen that plants use the scarcest nutrient or production factor more efficiently for the production of substances, the more the other factors are available in optimal conditions. Thus, there is a cross-connection between the influencing factors. In 1985 Georg Liebscher amended the Minimum Law with the Optimum Law to describe this increase in plant efficiency.
Humic acids help when the going gets tough
At this point humic acids come into play as the main biological component of humic substances. They are also helpful for growth when a resource is particularly scarce. Through their ability to form chemical complexes and bind nutrients, they improve the utilization of nutrients present in soil or feed. They support plants and animals, so to speak, in implementing the optimum law. Positive growth and health effects for plants and animals can thus be achieved even if the scarcest resource is not increased in its proportion.