NUTRIENTS AND LIMITING FACTORS

The terms 'nutrient' and 'limiting factor' summarise the results of an experiment in which increase in supply results in an increased respon se. By extension they are often - perhaps usually - used when the user believes that were such an experiment made it would have this charact eristic. If the supply is further increased the response diminishes an d may, eventually, become negative. 'Nutrient' and 'limiting factor' t herefore apply, strictly, only when the circumstances are specified: t hey cannot be attached to a particular substance without qualification . The claim that 'nitrogen is a nutrient (or limiting factor)' is inco mplete. All nutrients are limiting factors, but the reverse is not tru e. The widespread belief that only one factor can limit a complex proc ess at one time is demonstrably false in general, though it may someti mes be true in particular cases.