Abstract:

This research explored the effects of intercrop row configuration on light environment characteristics， yield， and light use efficiency （LUE） in maize/alfalfa intercropping， in order to provide recommendations for optimal planting pattern for farm use on the Loess Plateau. Five planting patterns were investigated： sole alfalfa （SA）， sole forage maize （SM）， one row of maize intercropped with two rows of alfalfa （I₁₂）， two rows of maize intercropped with two rows of alfalfa （I₂₂） and two rows of maize intercropped with four rows of alfalfa （I₂₄）， and the research included field experiments （in 2018 and 2019）， and mathematical simulation. The dry matter yield and canopy transmission of photosynthetically active radiation （PAR） for the five planting patterns were measured. A light transmission model considering the geometrical relationship between light angle and canopy structure was developed to simulate PAR transmission in each monoculture or intercropping system and measured values in field experiments were used to validate the light transmission model. The yield of monoculture alfalfa was significantly greater than that of intercropped alfalfa in 2018 （P<0.05）. However， in 2019 the production of alfalfa in I₁₂， I₂₂， and I₂₄ treatments was greater （197.8， 180.3 and 197.0 g·m^-2， respectively） than that in SA treatment （1473.5 g·m^-2）. The total dry matter yield of maize in I₁₂， I₂₂ and I₂₄ treatments， averaged over two years， was increased by 12.1%， 0.9% and 23.9%， respectively， compared with SM. The land equivalent ratio （LER） of all intercropped sowings was greater than 1.0 in 2019， indicating intercropping advantages. The radiation transmission model accurately simulated the PAR at the bottom of the maize/alfalfa canopy in intercropping systems. The mean absolute errors of simulation results and the corresponding root mean square errors were 59.0 and 66.6 μmol·m^-2·s^-1， respectively. The PAR reaching the top of the alfalfa canopy in intercropped plantings was significantly lower than that in SA （P<0.05）. LUE of maize in I₁₂， I₂₂ and I₂₄ were calculated as 52.5%， 9.3% and 51.7%， respectively， higher than that of SM in 2018， and 28.5%， 9.6% and 21.0%， respectively， higher in 2019 （P<0.05）. In 2019，LUE of intercropped alfalfa in I₁₂, I₂₂ and I₂₄ were 19.2%, 32.4% and 20.9% higher (P<0.05), respectively, than those of SA. In summary， appropriate maize/alfalfa intercropping patterns improved the light environment of intercropped alfalfa and enhanced crop LUE. It was found that the planting configuration I₂₄ was optimal for light transmission and system productivity. Thus， the I₂₄ planting regime is recommended be applied in areas with similar climate.

Key words: maize and alfalfa intercropping, photosynthetically active radiation, light transmission model, light interception, light use efficiency