Water goes down into the soil and pushes out the air.
The free water drains from the soil and sucks air back in. The most fertile natural soil for the production of good food for the welfare of man and his animals was in the natural grasslands where the rainfall was moderate. Where the rainfall was much below 16 inches annually the minerals necessary for the production of high quality complete protein were not so readily available. But where the rainfall exceeded 30 inches, the extra amount of water going down through the soil had not only speeded up the process for the release of the nutrients minerals, but had partially overcome the capacity of the organic matter in the soil to retain them. They were leached downwards to deeper levels in the earth or washed away.