Carrots
Liebig's Law of the Minimum, often simply called Liebig's law, states that growth is dictated not by total resources but by the scarcest resource which becomes the limiting factor (Justus von Liebig, 1873). This is often depicted as Liebig's barrel where the individual staves in a barrel represent nutrients or other limiting factors.
One approach to maintain the soil nutrient status is to calculate the removal in the harvested crop and ensure that these nutrients are replaced over the rotation cycle. The following table is a guide, but more accuracy can be achieved through actual laboratory analysis of harvested material.
A nutrient management plan should be focused on achieving the correct balance of the essential nutrients for optimal growth. That does not mean applying all 13, but correct use of diagnostic / analysis tools should be made to understand which of these 13 minerals is at yield-limiting supply levels.
See our fertiliser programmes for different field vegetable crops, begin by choosing which one.