One-time deep application of slow-release blended fertilizer delays post-anthesis senescence and improves wheat yield by optimizing soil nitrogen supply and root growth

In wheat-rice rotation systems, wheat production is constrained by cumbersome fertilization procedures, high nitrogen (N) leaching risk, and severe post-anthesis plant senescence, which limits the synergistic improvement of grain yield and N use efficiency. Therefore, a 3-year field experiment was conducted. With split application of normal urea (U) as the control treatment (CK), two fertilizer types (normal U and slow-release blended fertilizer (SRBF)) and two one-time fertilization methods (broadcast (B) and deep application (D)) were arranged to explore the field application performance of one-time deep application of SRBF. One-time application of SRBF increased soil inorganic N in the 0-40 cm soil layer from the jointing to maturity stage compared with one-time application of urea. Deep application enhanced inorganic N in the 0-40 cm layer, with D-U and D-SRBF increasing it by 3.94 and 11.86% relative to B-U and B-SRBF, respectively. D-SRBF treatment significantly increased root length density, root surface area density and root volume ratio in the 10-30 cm soil layer compared with other treatments, with average increases of 30.70, 33.25 and 52.65%, respectively. It also maintained higher post-anthesis root and leaf physiological activities, mainly due to improved soil inorganic N and root growth. Relative to CK, D-SRBF increased post-anthesis dry matter accumulation by 7.04% and yield by 5.82%, mainly via a 4.79% higher total grain filling mass. One-time deep application of SRBF optimizes soil N distribution and supply, improves root growth, and delays post-anthesis root and leaf senescence, which enhances population grain filling capacity and grain yield. Therefore, in rice stubble wheat, this fertilization strategy can serve as an effective alternative to split fertilization.