Border row effects on light interception in wheat/maize strip intercropping systems

In strip intercropping systems, different crop rows in a complete strip usually behave differently in growth dynamics and have distinct contribution to the final yield of the system, so resources capture and utilization processes of different crop rows should be treated separately in the performance evaluation of the whole system. This study was conducted to investigate the differences in light capture among different crop rows in wheat/maize strip intercropping systems. The field experiment comprised four planting patterns: monoculture wheat, monoculture maize, six rows of wheat alternated with two rows of maize (I62), and twelve rows of wheat alternated with four rows of maize (I124). A geometrical radiation transmission model was modified to estimate instantaneous light capture by different intercropped rows, which was tested with photosynthetically active radiation (PAR) measured above and beneath the intercrop canopy. The results demonstrated that the model accurately predicted PAR transmitted through the canopy with mean absolute error, root mean square error (RMSE) and normalized RMSE of 60.2 μmol m−2 s−1, 82.6 μmol m−2 s−1 and 5.2% respectively for I62 and of 65.9 μmol m−2 s−1, 95.3 μmol m−2 s−1 and 5.7% respectively for I124. With assistance of the model, we found that border rows in wheat strip intercepted far greater amount of both direct and diffuse PAR than the inner rows, whereas maize border rows showed no advantage in PAR absorption due to its canopy development was constrained by the competition from wheat strip. Canopy structure character showed positive effects on radiation interception in wheat border rows and all maize rows, and plant phenotypic plasticity showed positive effects on wheat border rows but negative effects on maize border rows. The radiation transmission model presented in this work was proved to be a useful tool for calculating spatial and temporal variability of radiation in strip intercropping systems and it can be further served as a base for modeling the plant growth dynamics in strip intercrops.