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Irrigation practices discussed on these pages relate to irrigation water conservation and, especially, irrigation application efficiency. Irrigation water conservation reduces the amount of water used in irrigation. In large part that happens by eliminating waste during application. Therefore, application efficiency is the ratio of water being withdrawn from a particular resource to the water available for use by the target crop. To be available, water must enter the soil under the crop where it can be taken up by roots. Application efficiency implies that an effort is made to reduce losses through a particular management or system change.

Irrigation Water Use Efficiency - WUE - (not explored extensively here) refers to improvements in the use of water that enters the soil for increasing yield. It is often measured as pounds of feed, fiber, or food produced per gallon of water. It is difficult to calculate in humid regions where rainfall provides much of the water available to crop roots.

Best Management Practices refer to those improvements that result in irrigation water conservation. In all irrigation systems, some water loss will still occur, i.e. not all water withdrawn from a source will reach the target plant roots. However, many losses can be minimized or eliminated through application of Best Management Practices. When these losses have been minimized for a particular system, then the application efficiency is maximized for that system.