Agricultural practices for crops can be classified as to cropping patterns, water management, tillage methods, nutrient supply, pest control and harvesting techniques. Cropping patterns consider such variables as seasonal or annual rotation, fallow periods, geometry of planted area, and monoculture versus polyculture planting. Choice among these patterns will affect the ability of soils to regenerate, the ability to sustain water supplies over an indefinite period and the total demand on external resources needed to sustain the activity.For example soil regeneration of one centimeter in depth requires approximately one millennium.
Water management choices may involve selection of groundwater, surface water or unirrigated strategies. Groundwater use is a method that must be very carefully constructed, since it may subject the aquifer to overdraft, potentially leading to catastrophic cessation of water yields; this phenomenon is currently observable in parts of the western plains in the USA (House. 2006) and on the North China Plain, as well as numerous other world regions. Furthermore, groundwater extraction generally requires a very high energy input in order to pump water to the root zone.