Applying silicon fertilizer under straw return can reduce nitrogen application, increase rice yield and lodging resistance

Straw return can improve soil nutrients but inhibits rice tillering. Nitrogen(N) fertilizer can alleviate tillering limitation, but excessive application may cause rice lodging and reduce yield. Silicon (Si) fertilizer can enhance lodging resistance of rice and promote its growth. However, it is still unclear whether the combined application of Si and N can alleviate the limiting effect of straw return on rice tillering, increase yield and lodging resistance. Therefore, we set up the experiment consisted of two Si levels of no Si (Si0) and 60 kg/ha of Si (Si1), and three N levels of 150 kg/ha (N1), 175 kg/ha (N2, Traditional N application), and 200 kg/ha (N3), for a total of six treatments. The results showed that compared with Si0, the average yield of N1 and N2 increased by 23.61% and 11.73% under Si1, respectively, while there was no significant difference in N3. Compared with Si0N2, rice yields of Si1N1, Si1N2, and Si1N3 increased by 11.00%, 11.82%, and 11.86%, respectively. This was mainly due to the increase in panicles per m2, leaf area index (LAI), and net photosynthetic rate (Pn). Among them, the partial factor productivity of applied N (NFP) of Si1N1 treatment was the highest, increasing by 36.46% compared to Si0N2. Meanwhile, Si1N1 reduced the lodging index (LI) compared to Si0N2, enhanced the stem’s lodging resistance, and reduced the LI by an average of 20.63%. The main reason was that it increases stem fullness, carbohydrate content, Si content, and clum wall thickness, enhances stem bending moment, and improves stem lodging resistance. Therefore, this study found that Si application can reduce N application by 14.28% and improve NFP, reduce the limiting effect of straw return on rice tillering. The recommended Si1N1 treatment (60 kg Si/ha combined with 150 kg N/ha) in the Northeast straw return rice region can achieve synchronous improvement in rice yield and lodging resistance under straw return. At the same time, the results of this study provide theoretical basis and technical support for the rational utilization of N fertilizer and sustainable development of agriculture in the Northeast rice region of China.