Intercropping of Indica and Japonica With Staggered Sowing Increases Rice Yield in the Yangtze and Huaihe River Basins in Henan, Central China

Intercropping systems that increase crop yield and land use efficiency are becoming increasingly popular worldwide, especially in developing countries. Despite many advantages related to nutrient, light, temperature, water, and land use efficiencies, intercropping of rice subspecies such as Indica and Japonica has not yet been fully explored. Hence, a two-year field experiment was conducted to study the effects of Indica–Japonica (i.e., XLY900-YY9 and YLY900-YY9) intercropping on the rice yield depending on sowing dates, and the intercropping effects were evaluated by yield, land equivalent ratio (LER), interspecific relative competitiveness (A), and relative crowding index (K). The Indica–Japonica intercropping at I1J1 sowing dates had cumulative yields of 12 t ha−1 (20%–23%) higher than the yield of Indica or Japonica under mono-cropping. This increase was mainly due to the efficient use of light and a higher photosynthetic rate. The LER values (1.23–1.27) and those of the relative crowding index (K) (1.69–5.36) were both greater than 1, indicating that intercropping used land more efficiently than mono-cropping. The interspecific relative competitiveness (A) showed Indica to be more competitive (A > 0, ranging from 1.05 to 1.80), while Japonica was less competitive (A < 0, ranging from −1.05 to −1.80), but with reduced overall competition between the two for light and land resources. Hence, Indica–Japonica intercropping has high potential to maximize rice yield while utilizing the natural resources more efficiently, and could contribute to food security, particularly in regions where rice is a staple crop. © 2025 Elsevier B.V., All rights reserved.