Picture Index for Field Verification of Crop Coefficientsby Jon Altenhofen, Northern Colorado Water Conservancy, District, Loveland, CO, USA,
David L. King, Northern Colorado Water Conservancy, District, Loveland, CO, USA,
Abstract: A picture index has been developed for eight irrigation crops to obtain reliable, rapid, and low-cost field determinations of crop growth stages and corresponding crop coefficient (Kc) values for improved calculation of crop evapotranspiration (ETc) values. The picture index is a series of photographs which follow each crop from emergence through effective cover (75 percent ground cover or shading). Each picture is described by a percent shading value determined by solar noon light bar measurements with corresponding mean and basal Kc values. The Kc values are determined by a linear increase of Kc with percent shading from the minimum Kc to the maximum Kc at 75 percent shading.
Subject Headings: Crops | Irrigation | Evapotranspiration | Vegetation | Field tests | Verification | Soil water | Water resources
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