|Camp Jr, Carl|
Submitted to: Encyclopedia of Water Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2002
Publication Date: 8/1/2003
Citation: SADLER, E.J., CAMP JR, C.R., HOOK, J.E. IRRIGATION MANAGEMENT IN HUMID REGIONS. Marcel Dekker, New York, NY. ENCYCLOPEDIA OF WATER SCIENCE. 2003.p. 478-482.
Interpretive Summary: Irrigation management includes deciding when to apply irrigation, and also how much to apply. Making these choices in humid regions is somewhat more complicated than in arid ones, primarily because of the possibility of receiving rain shortly after an irrigation. Besides being wasteful, this possibility also carries a risk of drainage and runoff carrying nutrients to groundwater or streams. Managing irrigation to save some room in the soil for possible rain requires a careful balance between crop needs and soil capacity, which can be limited by sandy soils or shallow rooting depths. Management methods leave storage space for potential rain by controlling a relatively narrow range of management allowed depletion. Doing so in humid regions can be achieved more easily using frequent, light irrigations instead of less-frequent, heavy ones commonly used in arid regions. Case studies of irrigation management in the SE USA showed that common methods, which include tensiometers, evaporation pans, and computer based water balances, can all work. Increases in irrigated area and interest in precision agriculture may combine to focus on spatially variable irrigation management in humid regions.
Technical Abstract: During the long history of irrigation, management of irrigation systems, which includes deciding how much irrigation to apply and when to do it, has been the subject of much study. Most of this work has been done in primarily arid areas, where the development of irrigation started earlier. However, current trends include increasing irrigated areas in humid regions, for which the contrasting climatic conditions require correspondingly different management techniques. In addition to having higher humidity, humid areas are generally more cloudy (lower solar radiation and thus lower evaporative demand), receive more rainfall, and tend to be cooler on average. However, during even short droughts, the conditions may be quite similar to those in arid regions. Dynamic weather complicates the management of irrigation systems in humid regions, forcing managers to trade off the possibility of rain against the need for irrigation. Management methods, whether soil based, crop based, or computer based, usually need to leave storage space for potential rain by controlling a relatively narrow range of management allowed depletion. Doing so can be achieved more easily using frequent, light irrigations instead of less-frequent, heavy ones commonly used in arid regions. Case studies of irrigation management in the SE USA serve to illustrate the common management methods, which include tensiometers, evaporation pans, and computer based water balances. Continuing trends of increasing irrigated area and increasing interest in precision agriculture may combine to focus on spatially variable irrigation management in humid regions.