Picture Index for Field Verification of Crop Coefficients

by Jon Altenhofen, Northern Colorado Water Conservancy, District, Loveland, CO, USA,
David L. King, Northern Colorado Water Conservancy, District, Loveland, CO, USA,

Document Type: Proceeding Paper

Part of: Development and Management Aspects of Irrigation and Drainage Systems


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 | Field tests | Verification | Irrigation | Evapotranspiration | Photography | Vegetation | Soil water

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