Some basics about nutrients
The famous barrel of Liebig having different height staves each representing a growth factor, is a simplified explanation of the fact that yield is dictated not by total resources available, but by the scarcest resource. This ‘law of the minimum’ is useful for understanding that it has not much sense to apply excessive amounts of nitrogen fertiliser when the crop in fact lacks calcium (or another element). This concept serves us well in advising fertilisation strategies as we know pretty well how much of each fertiliser element crops need at certain growth stages. Meanwhile, there still exists a large amount of uncertainty about which ratios to maintain between nutritive elements and about the uptake and use efficiencies of those elements under different circumstances. Scientific and practical knowledge about the minimum required levels of certain stimulants and microbes is basically missing although it is very clear that such compounds can have huge impacts on yield levels.
