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

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.