Regulatory mechanism of silicon application on phosphorus activation and uptake in the paddy soil-rice system

To investigate the regulatory mechanisms of silicon (Si) application on phosphorus (P) activation and uptake in the paddy soil-rice system, pot experiments were conducted using three waterloggogenic paddy soils from Changchun City of Jilin Province, Kunming City of Yunnan Province, and Hangzhou City of Zhejiang Province (designated as paddy soil 1, paddy soil 2, and paddy soil 3, respectively). The effects of different application amounts of Si (0, 30, and 60 mg/kg) on the P content in different parts of rice throughout the growth cycle, as well as yield, root iron plaque, and P availability and phosphatase activity in the rhizosphere soil were studied. The results showed that in paddy soil 1 and paddy soil 3, Si application significantly increased rice yield by 33.1%-115.0%, and enhanced P translocation to aboveground parts and grains. In paddy soil 1 and paddy soil 2, Si application significantly increased rice grain P levels by 11.0%-136.9%. Si application reduced the amount of P bound in root iron plaque by 6.3%-43.0% and decreased iron content in the plaque, with the most pronounced reduction (33.6%-47.6%) observed in the high-iron paddy soil 2. Furthermore, Si application increased alkaline phosphatase activity in paddy soil 3 by 95.9%-122.7%, enhancing the soil’s P mineralization potential. Overall, Si application improves rice growth, alters iron content in root iron plaques, mitigates iron toxicity to rice, particularly to the roots, and enhances soil P mineralization, thereby activating P in the paddy soil-rice system and increasing the efficiency of P uptake by rice plants.