Climate resource allocation and evolution of rice-oilseed rape double cropping system under different planting patterns in Anhui Province

Because the rice-oilseed rape double cropping system along the Yangtze River in Anhui Province shows tight stubble convergence together with light and temperature resources, it has attracted a lot of attention with regard to inter-seasonal climate resource allocation. Although transplanting and direct seeding are effective planting strategies for supplementing and deploying climate resources, the climate resource allocation and evolutionary characteristics in each growing season of different crops in rice-oilseed rape double cropping systems under different planting patterns as well as their adaptation to future climate change remain unclear. In this study, the inter-seasonal climate resource allocation and evolution characteristics as well as radiation-temperature production potential of the rice-oilseed rape double cropping system under different planting patterns were analyzed on the basis of meteorological datasets, such as air temperature, sunshine hours, total radiation, and precipitation, recorded from 1992 to 2022 at 27 meteorological stations along the Yangtze River in Anhui Province. The results showed that in the last 30 years, the inter-seasonal total radiation, sunshine hours, and photosynthetic production potential had decreased while the air temperature, rainfall, and radiation-temperature production potential had increased under the rice-oilseed rape double cropping system. In the rice season, the total radiation tendency rates under the transplanting and direct seeding pattern were −27.9 MJ·m⁻²·(10a)⁻¹ and −28.8 MJ·m⁻²·(10a)⁻¹, respectively. In the oilseed rape season, the total radiation tendency rates under the transplanting and direct seeding pattern were −40.5 MJ·m⁻²·(10a)⁻¹ and −26.6 MJ·m⁻²·(10a)⁻¹, respectively. During the rice season, the mean daily maximum temperature tendency rates under the transplanting and direct seeding pattern were 0.30 ℃·(10a)⁻¹ (P<0.05) and 0.24 ℃·(10a)⁻¹, respectively. The highest mean daily maximum temperature in the rice season reached 32.70 ℃ in 2022 (Qingyang County, Anhui Province, China). During the oilseed rape season, the mean temperature tendency rates were 0.36 ℃·(10a)⁻¹ (P<0.01) and 0.39 ℃·(10a)⁻¹ (P<0.01) under the transplanting and direct seeding patterns, respectively, with the mean temperature being higher under the transplanting pattern than under direct seeding. The tendancy rate of radiation-temperature production potential under direct seeding pattern was 170.2 kg·hm⁻²·(10a)⁻¹ in the oilseed rape season, which was higher than that under transplanting pattern. Thus, it appears that the direct seeding pattern has more potential to be explored for increasing yields in the oilseed rape season in the future. Both crop seasons within this double cropping system have faced problems, such as a continuous decline in light resources and a constant rise in air temperature. Adopting the transplanting pattern could increase the allocation of light and temperature resources to improve the radiation-temperature production potential by extending the crop reproductive period. Hence, the adoption of transplanting in both crop seasons would be an effective measure to cope with climate change and yield more production potential along the Yangtze River in Anhui Province. Meanwhile, delaying the transplanting date would be helpful to cope with warming at the oilseed rape seedling and rice flowering stages. Direct seeding resulted in less allocation of climatic resources than transplanting, and using high light-efficient varieties and building crop populations with efficient use of light resources are desirable.