NEW MEXICO CLIMATE CENTER

New Mexico Crop Information

Barley coefficient(kc) to calculate evapotranspiration(ET) where Et=kc*Eto

Eto = reference evapotranspiration or potential evapotranspiration referenced to grass.

Crop Coefficient uses growing degree days (GDD) accumulated from planting based on the averaging method of calculating GDD with a maximum temperature cutoff of 30 C and a minimum cutoff temperature of 5 C. The Base Temperature is 5 C.

The equation for the crop coefficient (kc) is: kc=5.70E-2 +3.23E-4 Gdd +3.94E-6 GDD^2-3.26E-9 GDD^3 with an R^2=0.93 based on data from Farmington NM. The crop coefficient equation is appropriate for a barley field with a yield around 7000 kg/ha. The point with a kc of 1.6 was not included in the regression analysis.

The reference for this work is Kallsen, Graig E., E. J. Gregory, T. W. Sammis. Oct. 1982. Water -Use production functions of selected agronomic crops in northwestern New Mexico, Phase II. New Mexico WRRI report No. 155