What is the main limiting factor in meadow biogeocenosis?

This is water.
The law of the limiting (limiting) factor, or the Liebig minimum law, is one of the fundamental laws in ecology, which states that the factor that is most significant for the body is the factor that deviates most from its optimal value, to a sharp deviation of which it is practically impossible to adapt to these conditions. It is from this, minimally (or maximally) presented at a given moment environmental factor, the survival of the organism. Other factors may be limiting at other times.
The factor that is farthest from the optimum is called limiting (limiting), for example, for plants in the steppe, in the meadow and in the desert, this is a lack of water, and in the spruce forest and at the bottom of the sea – a lack of light.