Improve the Simulation of Radiation Interception and Distribution of the Strip-Intercropping System by Considering the Geometric Light Transmission

Intercropping radiation interception model is a promising tool for quantifying solar energy utilization in the intercropping system. However, few models have been proposed that can simulate intercropping radiation interception accurately and with simplicity. This study proposed a new statistical model (DRT model), which enables the simulation of daily radiation distribution by considering the geometric light transmission in the intercropping system. To evaluate model performance, the radiation interception and distribution in two wheat/maize strip intercropping experiments (A and B) were simulated with the DRT model and other two statistical models, including the horizontal homogeneous canopy model (HHC model) and the Gou Fang model (GF model). Experiment A was conducted in different intercropping configurations, while Experiment B was conducted in soils with different salinity levels. In both experiments, the HHC model exhibited the poorest performance (0.120 < RMSE < 0.172), while the DRT model obtained a higher simulation accuracy in the fraction of photosynthetically active radiation (PAR) interception, with RMSE lower by 0.008–0.022 and 0.022–0.125 than the GF and the HHC models, respectively. Especially, the DRT model showed stronger stability than the other two models under soil salinity stress, with R2 higher by 0.129–0.354 and RMSE lower by 0.011–0.094. Moreover, the DRT model demonstrated a relatively ideal simulation of the daily radiation distribution in Experiment A (0.840 < R2 < 0.893, 0.105 < RMSE < 0.140) and Experiment B (0.683 < R2 < 0.772, 0.111 < RMSE < 0.143), especially when the continuous canopy formed during the later crop growth stages. These results indicate the superiority of the DRT model and could improve our understanding of radiation utilization in the intercropping system.