Optimized application of controlled-release nitrogen improves grain yield, nitrogen use efficiency, and lodging resistance in rice

Lodging is a primary factor limiting rice grain yield. How to achieve the synergistic improvement of high yield and nitrogen use efficiency without lodging has always been the focus worldwide. In this study, Yongyou 2640 (indica-japonica hybrid rice) and Jinxiangyu 1 (inbred japonica rice) were used as materials for field experiments across two years. Six different nitrogen managements were set up, including no nitrogen (T1), conventional urea (T2), controlled-release nitrogen (T3), reduction of controlled-release nitrogen (T4), controlled-release nitrogen combined with one-time basal conventional urea (T5), controlled-release nitrogen combined with split conventional urea (T6). The results showed that compared with T2, the combined application strategy of controlled-release nitrogen (T5 and T6) could improve nitrogen use efficiency and grain yield by 4.89–5.69% and 3.41–4.65%, respectively. The carbohydrate contents of the second basal internode, the internode breaking strength, the thickness of the epidermal silicon layer, the number of large and small vascular bundles, and the thickness of parenchymatous tissue and mechanical tissue were increased, whereas the internode length, bending moment and lodging index were reduced under the combined application strategy of controlled-release nitrogen. These results indicated that the combined application strategy of controlled-release nitrogen could achieve the goal of high yield and nitrogen use efficiency with synchronously increased stem strength due to the improvement in the morphological, mechanical, physicochemical and anatomical properties of second basal stem.