Crop coefficient (Kc) estimation from leaf area index (LAI)

I am studying a methodology to estimate Kc value for a large region using LAI remote sensing data.
At the Invest’s Manual there are 3 sets of equations that may be used for this purpose:

“Where Kc values are not available, they can be estimated using information about Leaf Area Index (LAI) over the growing season.
There are several relationships relating LAI to vegetation-specific Kc.
a) Kc = 1.1 * (1- EXP(-1.5*(LAI))) From WI irrigation scheduler workbook
b) Kc = 0.71LAI^0.5 – 0.2 (for LAI < 3.0).
or c) Where LAI can be measured or approximated, Kd can be approximated under normal conditions using an exponential function by Allen et al. (1998) used for estimating Kcb during midseason (Eq. 97 in FAO 56). The result is: Kc = (1-EXP(-0.7

I would like to know if there is a best choice among them? Has anyone tried this methodology?

Thank you,


Hi Julia,

I can’t say I’ve ever tried any of these methodologies myself, but where there are options here (and particularly given that you have a large region and are using remote sensing data), I might suggest taking a statistical approach to find the one that best reflects your region of interest based on known values, whether from the literature or from other trusted sources.

Maybe @swolny, would you have some more project-specific experience and suggestions here?

Hope this helps!

I haven’t used LAI to estimate Kc either, sorry I can’t be of help here.

~ Stacie