The footprints of water and nitrogen (WF and NF) provide a comprehensive overview of the type and quantity of water consumption and reactive nitrogen (Nr) loss in crop production.  In this study, a field experiment over two years (2019 and 2020) compared three integrated agronomic practice management (IAPM) systems: An improved management system (T2), a high-yield production system (T3), and an integrated soil–crop management system (ISCM) using a local smallholder farmer’s practice system (T1) as control, to investigate the responses of WF, Nr losses, water use efficiency (WUE), and nitrogen use efficiency (NUE) to IAPM.  The results showed that IAPM optimized water distribution and promoted water use by summer maize.  The evapotranspiration over the whole maize growth period of IAPM increased, but yield increased more, leading to a significant increase in WUE.  The WUE of the T2, T3, and ISCM treatments was significantly greater than in the T1 treatment, in 2019 and 2020 respectively, by 19.8–21.5, 31.8–40.6, and 34.4–44.6%.  The lowest WF was found in the ISCM treatment, which was 31.0% lower than that of the T1 treatment.  In addition, the ISCM treatment optimized soil total nitrogen (TN) distribution and significantly increased TN in the cultivated layer.  Excessive nitrogen fertilizer was applied in treatment T3, producing the highest maize yield, and resulting in the highest Nr losses.  In contrast, the ISCM treatment used a reduced nitrogen fertilizer rate, sacrificing grain yield partly, which reduced Nr losses and eventually led to a significant increase in nitrogen use efficiency and nitrogen recovery.  The Nr level in the ISCM treatment was 34.8% lower than in the T1 treatment while NUE was significantly higher than in the T1 treatment by 56.8–63.1% in 2019 and 2020, respectively.  Considering yield, WUE, NUE, WF, and NF together, ISCM should be used as a more sustainable and clean system for sustainable production of summer maize.

Characterizing the N uptake and utilization of different maize hybrids is essential for optimizing N application and increasing the profits from maize production.  Research trials were conducted with controlled-release urea (CRU) as a base fertilizer (TC) and urea split application in one (T1), two (T2), and three (T3) stages to evaluate the effects on N uptake, NUE, and yield using the ¹⁵N tracer technique between two maize hybrids; DH518 (an mid-early-maturing hybrid) and DH605 (a late-maturing hybrid).  According to the results, compared with urea, CRU as a base fertilizer and urea split application in two and three stages significantly increased grain yield and NUE while reducing environmental N loss.  Compared with T1, the grain yields of the TC, T2, and T3 treatments were, respectively, increased by 11.1, 9.8, and 11.7% in DH518 and by 16.4, 15.7, and 22.9% in DH605.  Regression analysis showed that the grain yield of DH518 displayed a bilinear trend of an initial rapid increase and then a slow increase with the increase in post-anthesis N accumulation, total N accumulation, N recovery efficiency, and N nutrition index (NNI).  By contrast, DH605 consistently showed a linear regression relationship with a rapid increase.  The crop recovery N efficiency (CRN) values in the T3 treatment for urea applied at the sowing stage and topdressing at the V9 stage in DH518 were 60.0 and 62.4% higher than under topdressing at the VT stage, respectively, while the CRN values of urea topdressing at the V9 and VT stages in DH605 were 37.7 and 37.1% higher than when applied at the sowing stage, respectively.  The higher pre-anthesis N demand and shorter growth period of DH518 maintained the N supply–demand balance, resulting in NNI (NNI≥0.988) falling within the range of slow yield increase under the T2 and TC treatments, while the N status of DH605 plants only reached optimal levels in the T3 treatment.  Therefore, a split three-stage application of urea or applying CRU as a base fertilizer and topdressing with urea in the later growth stages is recommended for mid-late-maturing hybrids to obtain an optimal yield.  In addition, for mid-early-maturing hybrids, applying CRU or reducing the number of times of split application, e.g., a split two-stage application, can ensure an adequate N supply in the later growth stages and increase production and thus profits.