Performance of evapotranspiration models for maize ― bare soil to closed canopy

Simulating evapotranspiration (ET) processes in agricultural crop systems requires dynamic models capable of describing the entire range of crop cover. The Shuttleworth and Wallace (S-W) ET model has the potential to fulfill this requirement, but it has not been rigorously tested on crops over the season. A field study assessed the seasonal performance of the Penman-Monteith (P-M) and the S-W ET models against Bowen ratio energy balance (BREB) measurements for irrigated maize during 1993 in Fort Collins, Colorado. The P-M performed poorly at low Leaf Area Index (LAI 2, and over the season, respectively. To facilitate the practical use of the S-W model, simplified and effective methods for determining soil and canopy resistances are needed.