Crop production (agriculture) has no single and simple origin. Crop productivity or production is the rate at which a crop accumulates organic matter per unit area per unit time. In crop production the aerial environment cannot be altered easily. Season for raising each crop has to be selected to attain highest productivity from the available climatic resource. Much of the crop production is lost because of unfavorable weather caused by temperature extremes, droughts, winds, or floods. A plant productivity depends on the production and use of assimilates. Management practices are developed for individual crops and recommendations are made for individual crops. The residual effects of individual crops are not considered in crop-based recommendation. A system consists of several components that depend on each other.