Light Competition in Chinese Cabbage/Maize Strip Intercropping Systems

Due to drastic socio-economic changes traditional intercropping systems in China are endangered. New high yielding intercropping systems that can easily be mechanized have to be developed. By using environmental resources more efficiently intercropping often produces higher yields compared to monocropping. Solar radiation as the strongest growth factor plays a key role when designing new intercropping systems. A Chinese cabbage – maize strip intercropping experiment was run at Hohenheim University’s research station “Ihinger Hof” in 2009. Photosynthetically active radiation (PAR) was measured regularly in the strips in different distances to the neighboring maize plants. However continuous and simultaneous measurements and thus the direct quantification of differences in daily available PAR were not possible. By adjusting polynomials to the measured timelines and defining sunrise and sunset as the interval borders the integrals of each polynomial could be calculated. Daily PAR was significantly reduced in the first three rows of Chinese cabbage grown next to maize; with the lowest values of 70% and 56% in row one west and east respectively. Reduced PAR led to significant yield decreases in these Chinese cabbage rows. To optimize the spacing in a maize/Chinese cabbage intercropping system PAR availability and tolerance of shading of the subordinate crop will be decisive.