[Allocation and Stabilization Responses of Rice Photosynthetic Carbon in the Plant-Soil System to Phosphorus...

This research studied the response of the input and allocation of photosynthetic carbon (C) to phosphorus (P) in paddy soils. Two treatments were conducted in this experiment:no P application (P₀) and the application of 80 mg·kg^-1 of P (P₈₀). The rice cultivar was the indica Zhongzao 39. The ¹³C-CO₂ continuous labeling technique was used to identify the photosynthetic C distribution of the rice. The results showed that the application of P₈₀ significantly increased the photosynthates allocation in the rice aboveground, but reduced their allocation in the rhizosphere soil (P<0.05). At the jointing stage, P₈₀ application increased the photosynthetic C content of the rice by 70%, but the root dry weight decreased 31%. Compared with P₀, the total C content of the aboveground rice was increased 0.31 g·pot^-1 by P₈₀. The ratio of rice roots to shoots decreased with the P₈₀ treatment. Moreover, P₈₀ application led to an increase in the photosynthetic microbial biomass in the non-rhizosphere soil C (¹³C-MBC) of 0.03 mg·kg^-1, but still decreased its allocation in the rhizosphere soil. The allocation of photosynthetic C to the particulate organic matter fraction (POC) and mineral fraction (MOC) in the non-rhizosphere soil showed no significant differences between P₀ and P₈₀. Additionally, the P₈₀ fertilization treatment significantly lowered the content of POC in the rhizosphere soil. In summary, P application increased the allocation of photosynthetic C in the soil-rice system, but reduced the accumulation of photosynthetic C in the soil. This research provided a theoretical basis and data supporting the rational application of P fertilizer, and was also of great significance as a study of the transportation and allocation of photosynthetic C and its sequestration potential response to the application of P to the rice soil.