Objectives Under the wheat-rice rotation system, returning crop straws to field stands as an primary utilization method for wheat and rice straws. Nevertheless, the incorporation of wheat straw often exert a detrimental impact on the growth and development of succeeding rice crops, owing to its limited decomposition time. We conducted a study on nitrogen management strategies aimed at fostering rice growth and accelerating wheat straw decomposition and nutrient release.

Methods Using rice cultivar 'Hongyang 5' as test material, a two-year field experiment (2022−2023) was conducted in Yangzhou, Jiangsu. Under conditions of wheat straw incorporation amount 9900 kg/hm² and total N application rate 270 kg/hm², five nitrogen management treatments with varying N ratios of basal: tillering: panicle fertilizers were established, including 3∶3∶4 (T1), 3.5∶3.5∶3 (T2), 4∶4∶2 (T3), 4.5∶4.5∶1 (T4), and 5∶5∶0 (T5), alongside a no-N control (CK). Tillering dynamics were monitored from beginning until stabilization. Rice population growth, dry matter accumulation, and N uptake were measured at key growth stages. Simultaneously, 100 g straw samples in nylon mesh bags were buried at a 5 cm depth of each treatment plot, with 9 bags per plot. The straw bags were retrieved at jointing, heading, and maturity stages to quantify straw decomposition (via weight loss) and N release (based on straw N content).

Results Among N management treatments, rice yield, effective panicles, spikelet number per panicle, and seed-setting rate followed a parabolic trend with rising basal−tillering N ratio. T2 achieved the highest values, significantly outperforming other treatments (except T3 in 2023). Over both years, T2 also exhibited the highest productive tiller rate and total dry matter accumulation, increasing by 2.59%−26.46% and 1.68%−10.80% on average, respectively, compared to other treatments. Straw decomposition and decomposition proportion during the transplanting−jointing stage increased with higher basal−tillering N ratios but declined gradually from jointing−heading and heading−maturity stages. Cumulative N release rates from wheat straw ranged 67.50%−70.32% (2022) and 72.88%−74.42% (2023), with T3 and T5 showing the highest averages. Rice N use efficiency (NUE) ranged 28.11%−44.79% across treatments, peaking at 44.26% under T2. During jointing−heading and heading−maturity stages, straw decomposition, decomposition proportion, and N release rates decreased with increasing basal−tillering N ratios. Excessive basal−tillering N suppressed N uptake and utilization in later growth stages, ultimately reducing NUE. Correlation, factor, and redundancy analyses confirmed that appropriate panicle fertilizer application mitigated N competition between soil microbes and rice plants during late growth stages, enhancing plant N content, N accumulation, seed-setting rate, and thereby boosting both yield and NUE.

Conclusions Under full wheat straw incorporation in the rice-wheat rotation system of Jiangsu Province, allocating 70%−80% of total N (270 kg/hm²) in medium−japonica rice season as basal−tillering fertilizer and 20%−30% as panicle fertilizer effectively promotes wheat straw decomposition and N release, facilitates dry matter accumulation and grain filling, and achieves synergistic improvement in rice yield and nitrogen use efficiency.