The Potential Role of Nitrogen Management in Enhancing Grain Yield and Lodging Resistance of Shanlan Upland Rice (Oryza sativa L.)

As a drought-resistant and water-saving rice (Oryza sativa L.), the Shanlan upland rice germplasm can provide solutions to the food security problems caused by frequent water shortages. In most nitrogen (N) fertilizer management strategies targeting maximum rice yields, lodging (both root and stem) is often ignored. Hence, this study aimed to determine an optimal N fertilizer management strategy that balanced the trade-off between yield and lodging in Shanlan upland rice. Our research employed the “safety factor” (SF) technique to explore the root-lodging resistance (represented by SFr) and stem-lodging resistance (represented by SFs) of Shanlan upland rice using three N fertilizer methods, including conventional N fertilization (CNF), split–postponed N fertilization (SPNF), and controlled-release N fertilizer (CRNF), and three N application rates (80, 120, and 160 kg N ha−1) for two consecutive years. Compared with CNF, the SFr improved by 14.9% for CRNF and 9.1% for SPNF. Likewise, the SFs increased by 22.7% for CRNF and 15.3% for SPNF. Moreover, Shanlan upland rice was found to be more prone to the risk of root lodging than stem lodging. At the same time, the grain yield and net benefit improved by 14.6% and 18.1% for CRNF, respectively, compared with CNF. Hence, employing the CRNF technique was more effective at reducing the lodging risk of Shanlan upland rice. Moreover, increasing the N application rate beyond 120 kg N ha−1 did not significantly increase the grain yield for CRNF but the lodging resistance and net benefit were reduced. In conclusion, with an N application rate of 120 kg N ha−1 for CRNF, Shanlan upland rice could achieve a relatively stable and high net income and can be recommended to growers for adoption.