Polypeptide urea increases rice yield and nitrogen use efficiency through root growth improvement

Context: Elucidating rice root growth and development characteristics is essential for improving nitrogen use efficiency (NUE) and grain yield (GY) of crops, particularly in light of innovations such as polyaspartic acid (PASP)-urea formulations. However, the effectiveness of PASP-urea on the morphological properties of rice roots is insufficiently explored. Objective: We aimed to examine the effect of PASP-urea on root morphology properties, NUE, and grain yield of mid-season rice in southwest China. Methods: In 2016 and 2017, a two-factor randomized block design experiment was conducted in Sichuan, China, during the rice planting season. Three N treatments: no N (control), conventional urea [CU], and polyaspartic acid-urea [PU] were administered to two rice varieties: Yixiangyou 2115 and Fyou 498. Results: Our findings showed that grain yield and nitrogen recovery efficiency (NRE) of rice were closely related to the root surface area density (RSAD), root length density (RLD), and root volume density (RVD) of rice. Compared to the CU treatment, the PU application significantly boosted the root dry matter weight, RLD, RVD, and RSAD of both varieties by 12.00-16.87 %, 0.16-28.98 %, 12.41-37.06 %, and 8.14-33.66 % at the jointing, heading, and maturity stages, respectively. This contributed to a 0.37-15.63 % and 23.45-48.12 % increase in grain yield and NRE, respectively, in both years, and a 12.26-15.69 % increase in N partial productivity efficiency (NPPE) in 2017 by improving the effective panicle number per unit area, spikelets per panicle, and N uptake. Conclusion: NRE and grain yield of rice were significantly increased by PU application by improving the rice root system. Implications: The study findings offer insight on how PASP-urea application influences the root morphology of rice and its relationship with grain yield and NRE while offering novel strategies and concepts for optimizing N use in rice cultivation.