In the field of ecology, a natural system is one that exists in nature, independent of any human involvement. The natural system consists of all the physical and biological materials and their intertwined processes. The study of natural systems is important to several fields, agriculture being one of them. Agriculture is an example of an artificial (man-made) system that is introduced into an existing natural system. While the agricultural system operates according to its man-made schedule and processes, it is nonetheless affected by fundamental natural processes such as weather, the ability of soil to produce crops, the feeding patterns of livestock and others.