Irrigation Science

, Volume 28, Issue 1, pp 17–34 | Cite as

Estimating crop coefficients from fraction of ground cover and height

  • Richard G. AllenEmail author
  • Luis S. Pereira
Original Paper


The FAO-56 procedure for estimating the crop coefficient K c as a function of fraction of ground cover and crop height has been formalized in this study using a density coefficient K d. The density coefficient is multiplied by a basal K c representing full cover conditions, K cb full, to produce a basal crop coefficient that represents actual conditions of ET and vegetation coverage when the soil surface is dry. K cb full is estimated primarily as a function of crop height. K cb full can be adjusted for tree crops by multiplying by a reduction factor (F r) estimated using a mean leaf stomatal resistance term. The estimate for basal crop coefficient, K cb, is further modified for tree crops if some type of ground-cover exists understory or between trees. The single (mean) crop coefficient is similarly estimated and is adjusted using a K soil coefficient that represents background evaporation from wet soil. The K c estimation procedure was applied to the development periods for seven vegetable crops grown in California. The average root mean square error between estimated and measured K c was 0.13. The K c estimation procedure was also used to estimate K c during midseason periods of horticultural crops (trees and vines) reported in the literature. Values for mean leaf stomatal resistance and the F r reduction factor were derived that explain the literature K c values and that provide a consistent means to estimate K c over a broad range of fraction of ground cover.


Leaf Area Index Crop Coefficient Stomatal Control Crop Height Density Coefficient 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


  1. Alba I, Rodríguez PN, Pereira LS (2006) Irrigation scheduling simulation for citrus in Sicily to cope with water scarcity. In: Rossi G, Cancelliere A, Pereira LS, Oweis T, Shatanawi M, Zairi A (eds) Tools for drought mitigation in Mediterranean regions. Kluwer, Dordrecht, pp 223–242Google Scholar
  2. Allen RG, Howell TA Snyder RL (2009) Irrigation water requirements. In: Irrigation, chap 5, 6th edn. Irrigation Association (in press)Google Scholar
  3. Allen RG, Pruitt WO, Businger JA, Fritschen LJ, Jensen ME, Quinn FH (1996) Evaporation and transpiration. In: Wootton et al (Task Com.) ASCE handbook of hydrology, chap 4, 2nd edn. American Society of Civil Engineers, New York, pp 125–252, 784 pGoogle Scholar
  4. Allen RG, Pereira LS, Raes D, Smith M (1998) Crop evapotranspiration: guidelines for computing crop water requirements, Irrigation and Drainage Paper 56. United Nations FAO, Rome, 300 p.
  5. Allen RG, Pereira LS, Smith M, Raes D, Wright JL (2005a) FAO-56 dual crop coefficient method for estimating evaporation from soil and application extensions. J Irrig Drain Eng ASCE 131(1):2–13CrossRefGoogle Scholar
  6. Allen RG, Pruitt WO, Raes D, Smith M, Pereira LS (2005b) Estimating evaporation from bare soil and the crop coefficient for the initial period using common soils information. J Irrig Drain Eng ASCE 131(1):14–23CrossRefGoogle Scholar
  7. Allen RG, Pruitt WO, Wright JL, Howell TA, Ventura F, Snyder R, Itenfisu D, Steduto P, Berengena J, Baselga Yrisarry J, Smith M, Pereira LS, Raes D, Perrier A, Alves I, Walter I, Elliott R (2006) A recommendation on standardized surface resistance for hourly calculation of reference ETo by the FAO56 Penman-Monteith method. Agric Water Manage 81:1–22Google Scholar
  8. Allen RG, Wright JL, Pruitt WO, Pereira LS (2007a) Water requirements. In: Design and operation of farm irrigation systems, chap 8, 2nd edn. ASAE MonographGoogle Scholar
  9. Allen RG, Tasumi M, Morse A, Trezza R, Wright JL, Bastiaanssen W, Kramber W, Lorite I, Robison CW (2007b) Satellite-based energy balance for mapping evapotranspiration with internalized calibration (METRIC)—applications. J Irrig Drain Eng 133(4):395–406CrossRefGoogle Scholar
  10. ASCE-EWRI (2005) The ASCE standardized reference evapotranspiration equation. In: Allen RG, Walter IA, Elliott RL, Howell TA, Itenfisu D, Jensen ME, Snyder RL (eds) American Society of Civil Engineers, 69 p, App. A-F and IndexGoogle Scholar
  11. Ayars JE, Johnson RS, Phene CJ, Trout TJ, Clark DA, Mead RM (2003) Water use by drip-irrigated late-season peaches. Irrig Sci 22(3–4):187–194CrossRefGoogle Scholar
  12. Bodner G, Loiskandl W, Kaul H-P (2007) Cover crop evapotranspiration under semi-arid conditions using FAO dual crop coefficient method with water stress compensation. Agric Water Manage 93(3):85–98CrossRefGoogle Scholar
  13. Cholpankulov ED, Inchenkova OP, Paredes P, Pereira LS (2008) Cotton irrigation scheduling in Central Asia: model calibration and validation with consideration of groundwater contribution. Irrig Drain 57:516–532CrossRefGoogle Scholar
  14. Consoli, Simona G, D’Urso, Toscano A (2005) Remote sensing to estimate ET-fluxes and the performance of an irrigation district in southern Italy. Agric Water Manage 81(3):295–314Google Scholar
  15. de Azevedo PV, da Silva BB, da Silva VPR (2003) Water requirements of irrigated mango orchards in northeast Brazil. Agric Water Manage 58:241–254CrossRefGoogle Scholar
  16. de Medeiros G, Arruda FB, Sakai E, Fujiwarab M (2001) The influence of crop canopy on evapotranspiration and crop coefficient of beans (Phaseolus vulgaris L.). Agric Water Manage 49(3):211–224CrossRefGoogle Scholar
  17. Descheemaeker K, Raes D, Allen RG, Nyssen J, Poesen J, Muys B, Haile M, Deckers J (2007) FAO-56 crop coefficients for semiarid natural vegetation in the northern Ethiopian highlands. Compl Report, Dept. Land Man., KUL Leuven, p 20 Google Scholar
  18. Doorenbos J, Pruitt WO (1977) Crop water requirements. Irrigation and Drainage Paper No. 24 (rev.) FAO, Rome, 144 pGoogle Scholar
  19. Er-Raki S, Chehbouni A, Guemouria N, Duchemin B, Ezzahar J, Hadria R (2007) Combining FAO-56 model and ground-based remote sensing to estimate water consumptions of wheat crops in a semi-arid region. Agric Water Manage 87(1):41–54CrossRefGoogle Scholar
  20. Fereres E (ed) (1981) Drip irrigation management. Cooperative Extension, University of California, Berkeley, Leaflet No. 21259Google Scholar
  21. Girona J, Marsal J, Mata M, del Campo J (2003) Pear crop coefficients obtained in a large weighing lysimeter. In: ISHS Acta Horticulturae 664: IV international symposium on irrigation of horticultural crops, 6 ppGoogle Scholar
  22. Girona J, Gelly M, Mata M, Arbones A, Rufat J, Marsal J (2005) Peach tree response to single and combined deficit irrigation regimes in deep soils. Agric Water Manage 72:97–108CrossRefGoogle Scholar
  23. Goodwin I, Whitfield DM, Connor DJ (2006) Effects of tree size on water use of peach (Prunus persica L. Batsch). Irrig Sci 24(2):59–68CrossRefGoogle Scholar
  24. Grattan SR, Bowers W, Dong A, Snyder RL, Carroll JJ, George W (1998) New crop coefficients estimate water use of vegetables, row crops. Calif Agric 52(1):16–21CrossRefGoogle Scholar
  25. Greenwood KL, Lawson AR, Kelly KB (2009) The water balance of irrigated forages in northern Victoria, Austrália. Agric Water Manage 96(5):847–858CrossRefGoogle Scholar
  26. Hanson BR, May DM (2006) Crop evapotranspiration of processing tomato in the San Joaquin Valley of California, USA. Irrig Sci 24(4):211–221CrossRefGoogle Scholar
  27. Hernandez-Suarez M (1988) Modeling irrigation scheduling and its components and optimization of water delivery scheduling with dynamic programming and stochastic ETo data. PhD dissertation, University of California Davis, DavisGoogle Scholar
  28. Howell TA, Evett SR, Tolk JA, Schneider AD (2004) Evapotranspiration of full-, deficit-irrigated, and dryland cotton on the Northern Texas High Plains. J Irrig Drain Eng ASCE 130(4):277–285CrossRefGoogle Scholar
  29. Hunsaker DJ (1999) Basal crop coefficients and water use for early maturity cotton. Trans ASAE 42(4):927–936Google Scholar
  30. Hunsaker DJ, Pinter PJ Jr, Cai H (2002) Alfalfa basal crop coefficients for FAO-56 procedures in the desert regions of the southwestern U.S. Trans ASAE 45(6):1799–1815Google Scholar
  31. Hunsaker DJ, Pinter PJ Jr, Barnes EM, Kimball BA (2003) Estimating cotton evapotranspiration crop coefficients with a multispectral vegetation index. Irrig Sci 22:95–104CrossRefGoogle Scholar
  32. Hunsaker DJ, Barnes EM, Clarke TR, Fitzgerald GJ, Pinter PJ Jr (2005) Cotton irrigation scheduling using remotely-sensed and Fao-56 basal crop coefficients. Trans ASAE 48(4):1395–1407Google Scholar
  33. Jensen ME, Burman RD, Allen RG (ed) (1990) Evapotranspiration and irrigation water requirements. American Society of Civil Engineers Manual No. 70, 332 pGoogle Scholar
  34. Johnson RS, Williams LE, Ayars JE, Trout TJ (2005) Weighing lysimeters aid study of water relations in tree and vine crops. Calif Agric 59(2):133–136CrossRefGoogle Scholar
  35. Kato T, Kamichika M (2006) Determination of a crop coefficient for evapotranspiration in a sparse sorghum field. Irrig Drain 55(2):165–175CrossRefGoogle Scholar
  36. Körner C, Scheel JA, Bauer H (1979) Maximum leaf conductance in vascular plants. Photosynthetica 13(1):45–82Google Scholar
  37. López-Urrea R, de Martín Santa Olalla F, Montoro A, López-Fuster P (2009a) Single and dual crop coefficients and water requirements for onion (Allium cepa L.) under semiarid conditions. Agric Water Manage 96(6):1031–1036CrossRefGoogle Scholar
  38. López-Urrea R, Montoro A, López-Fuster P, Fereres E (2009b) Evapotranspiration and responses to irrigation of broccoli. Agric Water Manage 96(7):1155–1161CrossRefGoogle Scholar
  39. López-Urrea R, Montoro A, González-Piqueras J, López-Fuster P, Fereres E (2009c) Water use of spring wheat to raise water productivity. Agric Water Manage. doi: 10.1016/j.agwat.2009.04.015
  40. Mutziger AJ, Burt CM, Howes DJ, Allen RG (2005) Comparison of measured and FAO-56 modeled evaporation from bare soil. J Irrig Drain Eng 131(1):59–72CrossRefGoogle Scholar
  41. Paço TA, Ferreira MI, Conceição N (2006) Peach orchard evapotranspiration in a sandy soil: comparison between eddy covariance measurements and estimates by the FAO 56 approach. Agric Water Manage 85(3):305–313CrossRefGoogle Scholar
  42. Pastor M, Orgaz F (1994) Los programas de recorte de riego en olivar. Agricultura no 746:768–776 (in Spanish)Google Scholar
  43. Pereira LS, Perrier A, Allen RG, Alves I (1999) Evapotranspiration: concepts and future trends. J Irrig Drain Eng ASCE 125(2):45–51CrossRefGoogle Scholar
  44. Pereira LS, Cai LG, Hann MJ (2003) Farm water and soil management for improved water use in the North China Plain. Irrig Drain 52(4):299–317CrossRefGoogle Scholar
  45. Popova Z, Eneva S, Pereira LS (2006) Model validation, crop coefficients and yield response factors for maize irrigation scheduling based on long-term experiments. Biosyst Eng 95(1):139–149CrossRefGoogle Scholar
  46. Raes D, Steduto P, Hsiao TC, Fereres E (2009) AquaCrop Reference Manual. Food and Agriculture Organization, Rome, 135 p.
  47. Ringersma J, Sikking AFS (2001) Determining transpiration coefficients of Sahelian vegetation barriers. Agrofor Syst 51:1–9CrossRefGoogle Scholar
  48. Ritchie JT (1974) Evaluating irrigation needs for southeastern U.S.A. In: Proceedings of irrigation and drainage special conference on American Society of Civil Engineers, pp 262–273Google Scholar
  49. Rogers JS, Allen LH, Calvert DJ (1983) Evapotranspiration for humid regions: developing citrus grove, grass cover. Trans ASAE 26(6):1778–1783, 1792Google Scholar
  50. Rolim J, Godinho P, Sequeira B, Rosa R, Paredes P, Pereira LS (2006) SIMDualKc, a software tool for water balance simulation based on dual crop coefficient. In: Zazueta F, Xin J, Ninomiya S, Schiefer G (eds) Computers in agriculture and natural resources (4th world congress, Orlando, FL), ASABE, St. Joseph, MI, pp 781–786Google Scholar
  51. Snyder RL, Eching S (2005) Urban landscape evapotranspiration. In: The California state water plan, vol 4. Sacramento, CA, pp 691–693.
  52. Snyder RL, Lanini BJ, Shaw DA, Pruitt WO (1989a) Using reference evapotranspiration (ETo) and crop coefficients to estimate crop evapotranspiration (ETc.) for agronomic crops, grasses, and vegetable crops. Cooperative Extension, University of California, Berkeley, Leaflet No. 21427, 12 pGoogle Scholar
  53. Snyder RL, Lanini BJ, Shaw DA, Pruitt WO (1989b) Using reference evapotranspiration (ETo) and crop coefficients to estimate crop evapotranspiration (ETc.) for trees and vines. Cooperative Extension, University of California, Berkeley, Leaflet No. 21428, 8 pGoogle Scholar
  54. Spohrer K, Jantschke C, Herrmann L, Engelhardt M, Pinmanee S, Stahr K (2006) Lychee tree parameters for water balance modeling. Plant Soil 284(1–2):59–72CrossRefGoogle Scholar
  55. Testi L, Villalobos FJ, Orgaza F (2004) Evapotranspiration of a young irrigated olive orchard in southern Spain. Agric For Meteor 121(1–2):1–18CrossRefGoogle Scholar
  56. Tolk JA, Howell TA (2001) Measured and simulated evapotranspiration of grain sorghum with full and limited irrigation in three High Plains soils. Trans ASAE 44(6):1553–1558Google Scholar
  57. Villalobos FJ, Orgaz F, Testi L, Fereres E (2000) Measurement and modeling of evapotranspiration of olive orchards. Eur J Agron 13:155–163CrossRefGoogle Scholar
  58. Wright JL (1982) New evapotranspiration crop coefficients. J Irrig Drain Div ASCE 108:57–74Google Scholar
  59. Yang D, Zhang T, Zhang K, Greenwood DJ, Hammond JP, White PJ (2009) An easily implemented agro-hydrological procedure with dynamic root simulation for water transfer in the crop–soil system: validation and application. J Hydrol 370(1–4):177–190CrossRefGoogle Scholar
  60. Zhao C, Nan Z (2007) Estimating water needs of maize (Zea mays L.) using the dual crop coefficient method in the arid region of northwestern China. Afr J Agric Res 2(7):325–333Google Scholar

Copyright information

© Springer-Verlag 2009

Authors and Affiliations

  1. 1.University of IdahoIdahoUSA
  2. 2.Technical University of LisbonLisbonPortugal

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