Objectives This study investigated the effects of one-time basal application of controlled-release urea (CRU) at different blending ratios on grain yield, dry matter accumulation, and nitrogen use efficiency (NUE) in spring maize under rainfed conditions in the Longzhong semi-arid region. The aim was to provide theoretical support for high-yielding and green and efficient fertilization practices in dryland spring maize.

Methods Field experiments were conducted in Baiyin of Gansu Province consecutively in 2023 and 2024, using the high-yielding spring maize cultivar ‘Xianyu 335’. The designed N application amounts included a no-nitrogen control (CK), and three dosages of 180, 225, and 300 kg/hm². Conventional urea treatments included the three N dosages and were applied in two splits, denoted as N180-U1, N225-U1, and N300-U1, respectively; one-time basal application treatments included two N rates (180 and 225 kg/hm²), with the blended ratios of CRU to conventional urea set at 1∶2 (N180-C1, N225-C1), 1∶1 (N180-C2, N225-C2), and 2∶1 (N180-C3, N225-C3). Plant samples were collected at the six-leaf (V6), ten-leaf (V10), silking (R1), milky (R3), and physiological maturity (R6) stages. The biomass and nitrogen content in various parts were measured to calculate nitrogen use efficiency parameters.

Results Under the three conventional urea treatments, the maximum grain yield was obtained at N 225 kg/hm². At the same N input, the two 1∶1 blending ratio treatments (N180-C2, N225-C2) recorded higher kernel numbers per ear and 100-kernel weight, thereby enhancing both yield and economic returns. Over the two years, the average yields under the N180-C2 and N225-C2 treatments were 7.92 and 8.44 t/hm², which were 4.76% and 8.34% higher than those under N180-U1 and N225-U1, respectively. Compared with N180-C2, the N225-C2 treatment increased yield by 6.57%, and boosted net income and the output/input ratio by 35.71% and 7.09%, respectively. The nitrogen input and blending ratios also significantly affected N content in stems, leaves, grains, bracts, and cobs at harvest, as well as N translocation from stems and leaves. The N225-C2 treatment recorded the highest values. At the 1∶1 blending ratio, the N180-C2 treatment recorded significantly higher nitrogen agronomic efficiency (NAE) and partial factor productivity (NPFP) than did N225-C2, with two-year average increases of 11.36% and 17.32%, respectively. Compared with the conventional fertilization treatment N225-U1, the N225-C2 treatment increased NAE, NPFP, apparent recovery efficiency, and N uptake efficiency by 14.72%, 7.36%, 34.25%, and 29.49% in 2023, and by 16.37%, 8.94%, 39.89%, and 19.78% in 2024.

Conclusions In the rainfed agricultural region of central Gansu, applying a blend of conventional urea and controlled-release urea as a single basal dressing at the optimal nitrogen rate (225 kg/hm²) enhanced nitrogen uptake and utilization in spring maize and promoted pre- and post-anthesis dry matter accumulation more effectively than split applications of conventional urea. The 1∶1 blending ratio outperformed the other ratios by improving pre-anthesis nitrogen and dry matter translocation, leading to higher grain yield and nitrogen accumulation, along with a significant increase in apparent nitrogen recovery efficiency. Thus, this fertilization strategy can serve as an effective nitrogen management approach for achieving high yield and high efficiency in spring maize production in the rainfed agricultural area of central Gansu.