The experimental design was a split plot in randomized complete blocks with three replicates. Three cropping systems (sole pea, sole maize and maize-pea strip intercropping) formed the main plots, and three N fertilizer management systems (N1, N2 and N3) with one control (N0, 0 kg N ha−1) formed the subplots. The sole maize treatment received N fertilizer at 450 kg N ha−1 as urea (46-0-0 of N-P2O5-K2O), with 20% of the total N (i.e., 90 kg N ha−1) evenly broadcasted and incorporated into the top 30 cm of soil using shallow rotary tillage prior to seeding (as base fertilizer), and the remaining 80% (i.e., 360 kg N ha−1) was divided into three portions as topdressing (implemented at typical maize growth stages, i.e., at jointing, pre-tasseling and 15 d post-flowering).