Optimizing Controlled-Release Urea and Conventional Urea Ratios Enhances Nitrogen Use Efficiency and Yield in Peanut

Combined application of controlled-release urea (CRU) and urea (U) improves yield and nitrogen use efficiency (NUE) in various crops, but the optimal blending ratio and related mechanisms in peanut production, particularly regarding antioxidant enzyme responses, remain insufficiently studied. To address this, a two-year field experiment was conducted with six fertilization treatments at a nitrogen rate of 120 kg·ha −1 : CK (no nitrogen), T1 (100% U), T2 (100% CRU), T3 (50% CRU + 50% U), T4 (70% CRU + 30% U), and T5 (30% CRU + 70% U). The results showed that compared with T1, the blended treatments significantly increased yield by 5.41–10.88% and improved NUE by 35.90–64.37%, with T4 performing the best. The T4 treatment significantly enhanced photosynthetic characteristics, promoted dry matter accumulation, coordinated nitrogen supply across growth stages, strengthened nitrogen metabolism enzyme activity, and delayed leaf senescence. At harvesting stage, the activities of SOD, POD, and CAT in T4 were 12.82%, 22.37%, and 23.32% higher, respectively, than those in T1, while MDA content decreased by 11.29%. This study demonstrates that in the ridge-furrow plastic film mulching cultivation system of Shandong’s brown soil, coapplying 70% CRU with 30% U is an effective nitrogen management strategy for peanuts. This approach achieves high and stable yields by improving nitrogen metabolism and antioxidant capacity. The findings provide a theoretical basis and technical reference for sustainable intensification of peanut production in similar ecological regions and cultivation systems.