A Guide to the Practical Use of Aerial Color-infrared Photography in Agriculture

Agricultural Applications of Color-infrared Film

Water

Fig. 13 - The dark green areas in the field indicate relatively moist conditions in the soil. The linear pattern is caused by tile drains located immediately below the soil's surface.

Although CIR film was designed, and is usually used, to enhance interpretations related to vegetative canopies, it does facilitate some interpretations related to surface water. Because near-infrared energy tends to be absorbed by water rather than reflected, wet spots in fields can be identified easily by their dark tones on a CIR air photo (fig. 13). For example, from an environmental-control standpoint, the extent and direction of feedlot runoff can be identified either because of the increased vegetative vigor in the path of the runoff or the variable, often unusual color of the polluted water running from the feedlot. Variations in turbidity and alkalinity, although not necessarily related to agricultural activities, are visible on CIR imagery (fig., 19). Also, areas under irrigation that are receiving little or no water, because of clogged sprinkler nozzles, for example, can be detected on the CIR photos.