Laserfiche WebLink
Department ®f Vater Resrces <br /> California Irrigation Management Information System <br /> Crop Coefficients (Kc) Explained <br /> Crop coefficients(Kc)are used with ETo to estimate specific crop evapotranspiration rates. The <br /> crop coefficient is a dimensionless number(usually between .1 and 1.2) that is multiplied by the. <br /> ETo value to arrive at a crop ET(ETc) estimate.The resulting ETc can be used to help an irrigation <br /> manager schedule when an irrigation should occur and how much water should be put back into <br /> the soil. An example calculation follows: <br /> If, ETo = 0.25 inches/day (for July 15, 1985) and, Kc = 0.55 (for an orange tree in July) <br /> then, ETc = ETo x Kc = 0.25 inches/da . <br /> y x 0.55 _ 0.1375 or 0.14 inches/day <br /> Crop coefficients vary by crop, stage of growth of the crop, and by some cultural practices. Citrus <br /> trees have smaller coefficients than peach trees (when the peach tree is at full cover). Coefficients <br /> for annual crops(row crops)will vary widely through the season,with a small coefficient in the early <br /> stages of the crop(when the crop is just a seedling)to a large coefficient when the crop is at full <br /> cover(the soil completely shaded).Almond orchards with cover crops between tree rows will have <br /> larger coefficients than almond orchards without cover crops. <br /> It is very important to understand that the crop coefficients that should be used with CIMIS ETo <br /> (with grass as the reference crop)are those that were developed specifically for use with <br /> grass-referenced ETo, <br /> �i <br /> The University of California Cooperative Extension has prepared two leaflets on crop coefficients.- <br /> Leaflet <br /> oefficients:Leaflet#21427- "Using Reference Evapotranspiration (ETo)and Crop Coefficients to Estimate <br /> Crop Evapotranspiration (ETc)for Agronomic Crops, Grasses, and Vegetable Crops"and Leaflet <br /> #21428- "Using Reference Evapotranspiration (ETo) and Crop Coefficients to Estimate Crop <br /> " Evapotranspiration(ETc)for Trees and Vines'. These crop coefficients are designed for use with <br /> CIMIS ETo information.These leaflets are available by contacting <br /> FCIMIS Help Line <br /> (800) 922-4647 <br /> Department of Water Resources <br /> Water Efficiency Office <br /> P.O. Box 942836 <br /> Sacramento, CA 94236-0001 <br /> Fill <br /> F <br /> Flo <br /> F! <br /> Notice last modified on March 24,2001 <br /> For more information,uisit www.cimis.water.ce.gov <br /> k <br />