Objectives Stabilized nitrogen fertilizers have showed acknowledged effects in yield increasing and nitrogen input reduction, but lack the targeted recommendation for different soil and climatic conditions. Therefore, we conducted experiment to propose the optimum rate of one-time application of stabilized nitrogen fertilizer in spring maize in central and southern Liaoning Province.

Methods Field experiments were carried out in Shenyang and Haicheng of Liaoning Province in 2017. The experimental nitrogen fertilizers were urea containing urease inhibitor and nitrification inhibitor. The treatments in both sites included no-nitrogen control (CK), ordinary urea control (CK1) and 10% less urea control (CK2), stabilized urea in application rates of 10%, 15% and 20% less than its CK1 (N 244 kg/hm²) treatment in Shenyang (S1, S2 and S3), and stabilized urea in rates of 10% and 15% less than its CK1 (N 217 kg/hm²) in Haicheng (S1 and S2). Soil and plant samples were collected in the main growing season of maize, respectively. The biomass and yield were investigated and the content of soil inorganic N and the N contents in different parts of maize plant were measured.

Results The treatments of stabilized fertilizer increased the maize yield significantly (P < 0.05), and S2 treatment showed the most stable and highest yield. The yield and income in S2 treatment were 7.5% and 1795 yuan/hm² more than those in CK1, and 11.1% and 2808 yuan/hm² more than those in CK2 in Shenyang. The yield in S2 in Haicheng site was not significantly different from that in CK1 and the income decreased by 184 yuan/hm², and the yield and income were increased by 19.5% and 2685 yuan/hm², compared with CK2. Compared with CK1, the nitrogen recovery efficiency (NRE), nitrogen agronomy efficiency (NAE) and nitrogen partial factor productivity (NPFP) of stabilized fertilizer treatments were increased by 10.4%–12.4%, 3.4%–6.2% and 6.5%–10.8%, and compared with CK2, the increases were 10.2%–12.2%, 3.3%–6.1% and 3.3%–7.6%. The stabilized urea significantly increased the N absorption intensity of maize in the middle and late growth stages. The total plant N accumulation intensity was in order of S2 > S1 > S3 > CK1 > CK2. The soil inorganic N contents (SIN) varied quite differently in 0–20 and 20–40 cm soil layers during the growing season. In the seedling and jointing stage of maize, the SIN contents of 0–20 cm layer in S1, S2 and S3 treatments were lower than those in CK1 and CK2, but from bell-mouthed stage to mature stage, the SIN contents of 0–40 cm soil layer were significantly higher. Generally the SIN content of the 0–40 cm soil layer in S1, S2 and S3 treatments varied less than that of ordinary urea treatment.

Conclusions Stabilized nitrogen reduction can maintain or increase soil inorganic nitrogen content. At the experimental site in Shenyang , the maize yield and economic benefit, total N accumulation and agricultural efficiency of nitrogen fertilizer are all highest when using stabilized urea at 15% less rate, while At the experimental site in Haicheng, the optimum recommendation for stabilized urea is 10% less as the relatively low conventional urea application rate in the area.