Modeling evapotranspiration in maize/soybean strip intercropping system with the evaporation and radiation interception by neighboring species model

An experiment was carried out at Shangqiu Agro-Ecosystem experimental station in 2008-2009 to determine the partitioning of evapotranspiration in a maize/soybean intercropping. Sap flow gauges and micro-lysimeters, were used to determine plant transpiration and soil evaporation. Average daily soil evaporation in the intercropping system during the observation period (from June 1 to June 30) in 2008 and 2009 seasons were 2.07 and 2.41 mm d−1, respectively. During the observation period, the mean transpiration rates of maize and soybeans in the intercropping arrangement were 1.47 and 0.78 mm d−1, respectively. A multi-source model - the ERIN (evaporation and radiation interception by neighboring species), was used to simulate soil evaporation and plant transpiration in the maize/soybean intercropping. Results showed that the ERIN model overestimated plant transpiration of maize and soybean, while the mean bias error (MBE), the root mean square error (RMSE) and the index of agreement (d) were 0.06 mm d−1, 0.23 mm d−1 and 0.93, respectively. However, the ERIN model underestimated soil evaporation; MBE, RMSE and d were −0.02 mm d−1, 0.44 mm d−1 and 0.97, respectively. Sources of error were attributed to the uncertainties in characterizing the micrometeorological conditions and specifying the empirical parameters of the resistance terms. The multi-source model was extremely sensitive to the water vapor deficit at canopy source height and the radiation captured by crop and stomatal resistance. Overall, the ERIN model is useful in simulating the partitioning of evapotranspiration in intercropping systems.