[Simulation of instantaneous light transmission in wheat/maize intercropping canopy in Hetao region, China].

The leaf distribution in intercropping canopy is usually laterally and vertically heterogeneous, which makes continuous measurement of light interception very difficult. In order to quantify the light interception by wheat/maize intercropping during different growth stages, a geometrical model was developed in this study to simulate photosynthetically active radiation (PAR) transmission in this system. Measured PAR values in field experiments were used to validate the geometrical model. Results showed that the geometrical model efficiently simulated the PAR transmitted on soil surface under intercropping canopy. The determination coefficients of linear regression between estimated and measured values were 0.947 and 0.950 for 6:2 intercropping (I62) and 12:4 intercropping (I124), respectively. The values of PAR intercepted by I62 intercropping system in 2012 and 2013 were 1061.4 and 924.3 MJ · m(-2), respectively, which were the highest among all cropping systems. The radiation caption ratios (RCRs) of I62 and I124 relative to sole crops were 1.29 and 1.19 during 2012 growing season, and 1.21 and 1.16 during 2013 growing season, respectively.