Monoculture was planted with row spacing and plant density for maize (MM) of 1.0 m and 58,500 per hectare (ha.) and for soybean (MS) of 0.5 m and 117,000 per ha. The plant spacing was 17 cm for all treatments, with a post-emergence density of 1 maize and 1 soybean plant per hole for the corresponding monocultures. The post-emergence density was 1 maize and 2 soybean plants per hole for maize-soybean relay strip intercropping. The plant density per unit area was equal for intercropping and the corresponding monocultures. All plots were planted with three strips that were 6 m in length and 2 m in width. The total number of plots was 27. In the maize-soybean relay strip intercropping system (IMS), a wide-narrow row planting (160 cm for wide rows and 40 cm for narrow rows) was adopted, resulting in a total ratio of maize to soybean rows of 2:2. Maize plants (IM) were in the narrow rows with row spacing of 40 cm, and soybean plants (IS) were in the wide rows with row spacing of 40 cm. Additionally, the distance between maize and soybean rows was 60 cm (Fig 2).