Silicon in soil and its interaction with nitrogen, phosphorus, and potassium nutrients on rice yield: A case study of paddy fields in the Taihu Lake region, China, without a history of silicon fertilization

The fact that the addition of silicon (Si) facilitates higher yields has been widely elucidated by academics. However, the effects and processes of plant-available Si (PASi) deficiency in soils on rice yield changes are still not fully understood. This study investigated the Si nutrient status of soils and rice in typical rice cultivation systems without the history of traditional Si fertilization in the Taihu Lake area of China (2020, 2021) and extensively discussed the interaction of Si with nutrient elements (N, P, K) and their effects on rice yield. Our results indicate that the PASi supply of paddy soils in this region has decreased significantly over the last four decades, which limits Si utilization by rice plants (especially straw and husk). In this case, the distribution and transfer of N, P, and K in the soil-plant system are partly related to the abundance of soil PASi (also controlled by soil parameters, e.g., SOM, pH and clay), with the combined effect of their interactions on rice yield being much greater than Si alone. The Partial Least Squares Path Modeling (PLS-PM) identified possible pathways of PASi effects on rice yield: (1) The direct path of increasing PASi to improve yield is not significant, indicating that the current soil PASi status is not sufficient to be responsible for the yield increase. (2) Indirect effects of PASi on yield components (height, filled grain rate) cause yield reduction. (3) The key potential pathway for yield increases is to promote nutrient transfer from straw to grain by increasing soil PASi. Given these results, in order to ensure sustainable rice productivity, Si-preserving techniques (eg., straw composting, Si fertilizer) might be advisable to improve soil PASi supply capacity while considering field management (e.g., irrigation, liming, straw return) to regulate the paddy soil environment to synergistically improve the Si and nutrient utilization efficiency of the soil-plant system.