Objectives To explore the effects of one-time root-zone fertilization (RZF) of urea nitrogen and controlled-release urea nitrogen on yield increase and efficiency improvement of maize, so as to provide a theoretical basis for simplified fertilization of maize.

Methods Maize field experiments were conducted in Jingzhou, Hubei Province in 2021−2022. The treatments included no nitrogen fertilizer (CK) and farmer fertilizer practice (FFP, split application of urea) controls, and three one-time root-zone fertilization (RZF) of common urea (UR), controlled release urea at the same rate (CRUR), or CRUR at rate of 25% reduction (75%CRUR). Acrossing V6−R1 growing stage of maize, plant height, stem diameter, leaf area index (LAI) and SPAD, and the activities of nitrate reductase (NR) and glutamine synthetase (GS) were measured. The grain yield and biomass were investigated, and nitrogen content was analyzed for calculation of nitrogen use efficiencies.

Results Compared with FFP, the RZF of controlled release urea treatments (CRUR and 75%CRUR) decreased plant height at the early growth stage of maize, increased LAI during V6−R1 growth stage by 18.9%−113.0% and 6.5%−67.3% in 2021 and 2022, respectively. UR treatment did not impact the stem diameter and SPAD values significantly, but CRUR treatment increased SPAD significantly. In addition, CRUR also exhibited the highest NR and GS activities, which were 35.9%−40.5% and 31.4%−73.5% higher than FFP, 15.0%−27.1% and 12.1%−44.7% higher than UR; compared with the 75%CRUR treatment, it significantly increased NR activity by 18.9%−21.8%. At the VT and R1 stages, compared with the 75%CRUR treatment, it significantly increased GS activity by 11.6% and 10.8%, respectively. UR treatment was harvested comparable maize yield with FFP in 2021 and 2022, 75%CRUR increased yield by 9.5% in 2021, while CRUR increased yield by 11.6% and 8.8% in 2021 and 2022, respectively, mainly through the increased number of grains per ear. CRUR and 75%CRUR treatments did not impact row number and the number of grains per row, but reduced the bald tip length significantly, only UR reduced the spike length (2022). Compared with FFP, CRUR and 75%CRUR treatments increased nitrogen use efficiencies in 2021 and 2022, in 75%CRUR treatment, the increase range of partial factor productivity of N (PFPN) by 46.1% and 41.1%, N agronomic efficiency (NAE) by 106.9% and 72.2%, and fertilizer contribution rate (FCR) by 39.3% and 34.7%, respectively. The nitrogen fertilizer use efficiency did not shown a significant improvement in UR treatment. And the nitrogen use efficiency was in order of 75%CRUR>CRUR>UR.

Conclusions One-time root-zone application of controlled-release urea (CRUR) could significantly increase maize yield and nitrogen use efficiency under reduced cost of fertilization. Under the technology, the conditions of nitrogen fertilizer reduction still need confirmed for maintaining high maize yield.