Assessment of Yield and Nitrogen Utilization of the Mixed CRU and Urea in Wheat–Maize Production in a 5-Year Field Trial

To identify the general pattern of impact of the application of the mixed controlled-release urea (CRU) with urea (C-U) on grain yield, plant characteristics, NUE and soil nitrogen contents in wheat–maize production, a 5-year field trial with three release longevity and four ratios of CRU in C-U and common urea alone (U) was carried out in the North China Plain. Results with meta-analysis revealed that C-U had significant effects on grain yield and plant characteristics, NUE and soil NO 3 − -N contents in wheat–maize production positively with the release longevity of CRU and the ratio of CRU-N in C-U. The application of C-U with 60 d or 90 d CRU for wheat and maize had the best overall effects, while C-U treatment with 30 d CRU had a significant inhibitory effect. For maize, C-U with 30% CRU-N had the largest increase rate on yield, 1000-grain weight, plant height, dry weight and NUE by 5.13%, 1.61%, 3.70%, 11.33%, and 8.63%, respectively, while C-U with 40% CRU-N had the largest reduction soil NO 3 − -N. For wheat, the application of C-U with 40% CRU-N had a significant effect on yield, sterile spikelet number, and NUE by 4.45%, −9.76%, and −8.04%, respectively. To conclude, the use of the C-U with appropriate release longevity and the ratio of CRU has great potential to proliferate wheat–maize yields and reduce fertilizer loss especially for maize that not only provides an effective generic methodology for agriculture to improve measures but also ensures profitability.