Legacy effect of elevated CO2 and N fertilization on mineralization and retention of rice (Oryza sativa L.) rhizodeposit-C in paddy soil aggregates

• Published in: Soil Ecology Letters 2022-03, Vol.4 (1), p.78-91
• Main Authors: Li, Yuhong, Yuan, Hongzhao, Chen, Anlei, Xiao, Mouliang, Deng, Yangwu, Ye, Rongzhong, Zhu, Zhenke, Inubushi, Kazuyuki, Wu, Jinshui, Ge, Tida
• Format: Article
• Language: English
• Subjects: Aggregates; Bioavailability; Biomass; Carbon 13; Carbon dioxide; Carbon dioxide concentration; Clay; Clay minerals; Earth and Environmental Science; Ecology; Environment; Fertilization; Growing season; Microorganisms; Mineralization; Organic carbon; Organic soils; Oryza sativa; Research Article; Retention; Rice; Rice fields; Silt; Soil aggregates; Soil Science & Conservation; Soil-plant interactions; Soils
• ISSN: 2662-2289; 2662-2297
• DOI: 10.1007/s42832-020-0066-y

Rhizodeposits in rice paddy soil are important in global C sequestration and cycling. This study explored the effects of elevated CO 2 and N fertilization during the rice growing season on the subsequent mineralization and retention of rhizodeposit-C in soil aggregates after harvest. Rice ( Oryza sativa L.) was labeled with 13 CO 2 under ambient (400 ppm) and elevated (800 ppm) CO 2 concentrations with and without N fertilization. After harvest, soil with labeled rhizodeposits was collected, separated into three aggregate size fractions, and flood-incubated for 100 d. The initial rhizodeposit- 13 C content of N-fertilized microaggregates was less than 65% of that of non-fertilized microaggregates. During the incubation of microaggregates separated from N-fertilized soils, 3%–9% and 9%–16% more proportion of rhizodeposit- 3 C was mineralized to 13 CO 2 , and incorporated into the microbial biomass, respectively, while less was allocated to soil organic carbon than in the non-fertilized soils. Elevated CO 2 increased the rhizodeposit- 13 C content of all aggregate fractions by 10%–80%, while it reduced cumulative 13 CO 2 emission and the bioavailable C pool size of rhizodeposit-C, especially in N-fertilized soil, except for the silt-clay fraction. It also resulted in up to 23% less rhizodeposit-C incorporated into the microbial biomass of the three soil aggregates, and up to 23% more incorporated into soil organic carbon. These results were relatively weak in the silt-clay fraction. Elevated CO 2 and N fertilizer applied in rice growing season had a legacy effect on subsequent mineralization and retention of rhizodeposits in paddy soils after harvest, the extent of which varied among the soil aggregates.