Blackman gave the law of limiting factors. The law expresses that when a process depends on a number of factors, the rate of the process depends on the slowest factor. Limiting factors are the factors that limit production. These are common nutrients, water or light. In reality, it is more complex, but it is common to consider limiting factors in terms of Liebig's "law" of the minimum, which suggests that there will always be one resource that is in shorter supply than others, and the supply of that limiting asset controls all other factors.